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1
Fish, Paul Vincent. "Synthetic studies towards marine metabolites." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235997.
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Pathirana, Induruwa Charles. "Secondary metabolites from selected marine organisms." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/27506.
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Marine organisms are known to produce secondary metabolites which have novel structures and are often biologically active. Chemical studies of biologically active metabolites from three different marine organisms led to the discovery of six new compounds and six previously known compounds.
The brown alga Dictyota binghamiae is fairly abundant in British Columbia coastal waters. A chemical study of this alga yielded ten diterpenoids of which four are new compounds. All the new compounds, dictyoxide A (66), dictyol G acetate (68), dictyotriol A diacetate (69), and epidictyol B acetate (70) contain a perhydroazulene carbon skeleton first encountered in the algal metabolite pachydictyol A (29). Dictyoxide A (66) appears to be an artifact of isolation. The acetates 68, 69, 70 were found to be antibacterial and antifungal. Six previously known compounds pachydictyol A (29), dictyol C (32), dictyoxide (35), acetyldictyolal (49) and the acetals 61a and 61b were also isolated from this alga.
Chemical studies on an Agelas sp. of sponge collected in Sri Lanka yielded the antimicrobial metabolite desbromooroidin (79).
An interesting interaction between the starfish Dermasterias imbricata and the sea anemone Stompia coccinea was observed a long time ago. When contacted by the starfish, the anemone displays an unusual "swimming" response which was, according to other subsequent studies, caused by a single chemical substance in the starfish. A study conducted to elucidate the structure of this starfish metabolite led to the isolation of imbricatine (91), a unique benzyltetrahydroisoquinoline alkaloid. Imbricatine (91) induced S. coccinea swimming response at a very low concentration and also exhibited antitumor activity.
Structures of all the new metabolites were determined by spectral analysis, and chemical degradations and chemical interconversions.Science, Faculty of
Chemistry, Department of
Graduate
3
Wojnar, Joanna M. "Isolation of new secondary metabolites from New Zealand marine invertebrates : a thesis submitted to the Victoria University of Wellington in fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry /." ResearchArchive@Victoria e-Thesis, 2008. http://hdl.handle.net/10063/630.
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Mostafa, Wael M. Abdel-Mageed. "Investigations of secondary metabolites from marine organisms." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources. Online version available for University member only until Sep. 1, 2014, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=53365.
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Miao, Shichang. "Novel secondary metabolites from selected marine invertebrates." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/31133.
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Chemical studies of a Northeastern Pacific tunicate and three Papua New Guinea sponges have led to the isolation of sixteen new secondary metabolites. The structures of the new compounds were determined by spectroscopic analysis and chemical interconversions. The absolute stereochemistry of imbricatine, a previously reported starfish metabolite, has also been determined.
The northeastern Pacific tunicate Ritterella rubra has been found to contain a novel series of aromatic butenolides, rubrolides A-H (149-156). The structures of the rubrolides were solved by the analysis of NMR (¹H, ¹³C, COSY, nOe, HETCOR, FLOCK, HMQC and HMBC), MS and IR data combined with chemical interconversions. FLOCK, a new ¹H/¹³C long-range correlation experiment, played a key role in establishing the rubrolide carbon skeleton. The rubrolides represent the largest family of non-nitrogenous tunicate metabolites. The protein phosphatase inhibitory activity and the potent antibiotic activities of the rubrolides warrant further investigation.
The absolute stereochemistry of imbricatine (179), a compound reported from the starfish Dermasterias imbricata, has been determined by comparing the optical properties of its chemical degradation products with those of model compounds. Raney nickel reduction of 179 yielded benzyltetrahydroisoquinoline 188a which was methylated to give 188b. Comparison between the CD spectrum of 188b and those of model compounds 189 and 190 solved the absolute stereochemistry of the tetrahydroisoquinoline fragment of 179. Reductive hydrolysis of 179 followed by oxidation yielded histidine disulphide 182. Comparison of the optical rotation of 182 with the reported value solved the absolute stereochemistry of the histidine fragment of 179. Attempts to study the biogenesis of 179 were unsuccessful.
Examination of three Papua New Guinea sponges resulted in the isolation of eight new compounds. Six new bastadins (211-216) were isolated from Ianthella basta. The structures were elucidated by spectroscopic analysis as well as comparison with the previously reported bastadins. A Xestospongia species was found to contain xestospongin E (238), a new metabolite, and a number of known xestospongins. Both the bastadins and the xestospongins possess antibiotic and cytotoxic activities. A symmetrical enyne, callydiyne (247), was isolated from Callyspongia flammea. The structure of 247 was determined by spectroscopic studies.Science, Faculty of
Chemistry, Department of
Graduate
6
Tischler, Mark. "Secondary metabolites from selected British Columbian marine organisms." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26650.
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The two purine alkaloids, phidolopin (36) and desmethylphidolopin (37), originally isolated from Phidolopora pacifica, were synthesized in order to produce sufficient quantities of the natural products for extended biological and pharmacological screening and to confirm the previous structural assignment of 37 which was based on spectral data.
Various combinations of phidolopin (36), desmethylphidolopin (37), 4-hydroxymethyl-2-nitrophenol (38) and 4-methoxymethyl-2-nitrophenol (39) were isolated from four different species of bryozoans, Diaperoecia californica, Heteropora alaskensis, Tricellaria ternata and Hippodiplosia insculpta. A dietary origin is suggested for these metabolites. The red sponge, Anthoarcuata graceae yielded six novel steroids including the ∆⁴-3,6-diketosteroids 116, 117, the A-nor steroids anthosterone A (118) and anthosterone B (119) as well as two diosphenol containing steroids, 120 and 121. The proposed structures were based on a combination of spectral analysis, chemical interconversions, synthesis, and single crystal X-ray diffraction analysis.Science, Faculty of
Chemistry, Department of
Graduate
7
Morris, Sandra Anne. "Novel secondary metabolites isolated from selected marine invertebrates." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/31073.
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A study of the secondary metabolism of two northeastern Pacific sponges and two Sri Lankan nudibranchs has led to the isolation of thirteen new and one previously known natural products. The structures of all of the compounds were determined by a combination of spectroscopic data analysis and chemical interconversions.
A study of the chemistry of the northeastern Pacific sponge Hexadella sp. has resulted in the isolation of six new brominated alkaloids. Two of these, hexadellins A (77) and B (78), are derived from dibromotyrosine. The structures of compounds 77 and 78 were determined via their acetylated derivatives 79 and 80. Four compounds possessing novel bis(indole) structures have also been isolated. Topsentin B2 (74) was isolated as a mixture of two slowly interconverting tautomers, 74a and 74b. Methylation of 74 resulted in the production of trimethyltopsentin B2 (75); the structure of 75 was determined spectroscopically. The structures of dragmacidons A (81), B (82), and C (83) were determined by a combination of spectral data interpretation and chemical interconversions. Dragmacidon C (83) was originally incorrectly assigned as 88; the correct structure was determined based upon synthesis of the model compound 94. Compounds 77 and 78 possess antimicrobial activities. Compounds 74 and 81 show considerable cytotoxic and antineoplastic activities.
Five new triterpene glycosides have been isolated from the northeastern Pacific sponge Xestospongia vanilla. The structures of isoxestovanin A (125), xestovanin C (127), dehydroxestovanin A (129), epi-dehydroxestovanin A (131), and dehydroxestovanin C (132) were all determined by a combination of spectral data interpretation and chemical interconversions. These compounds all contain the deoxy sugars L-rhamnose and D-fucose. Isoxestovanin A (125) possesses a new carbon skeleton and xestovanin C (127) and dehydroxestovanin C (132) possess linear
trisaccharide fragments which have not been previously encountered in triterpene
glycosides isolated from X. vanilla.
The Sri Lankan nudibranch Chromodoris glenei has yielded the known compound 12-desacetoxyshahamin C (153) and the new metabolite shahamin K (155). Both compounds possess dendrillane diterpene skeletons. The compound chromodorolide B (156) was isolated from specimens of Chromodoris cavae. It is only the second known diterpene natural product possessing the chromodorane skeleton.Science, Faculty of
Chemistry, Department of
Graduate
8
Dewi, Ariyanti Suhita. "Biologically active secondary metabolites from tropical marine invertebrates." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/15299.
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In our effort to discover promising anticancer agents, we have screened a series of
compounds for their activities as indoleamine-2,3-dioxygenase (IDO) inhibitor and SHcontaining
inositol 5-phosphatase (SHIP1) activator. In comparison to aaptamine (2.1) and
demethylaaptamine (2.2), isoaaptamine (2.4) from Aaptos cf. suberitoides appears to be the most
promising IDO inhibitor with an IC₅₀ of 0.00215 mg/mL, owing to the presence of hydroxyl
group at C9 position and the methylation at N1 position. A study on the sponge extract of RJA
55275 for its SHIP activator yielded theonellapeptolide Id (3.4), the first peptide that enhanced
the SHIP with 25% activity at concentration 124 μM, thus makes it the most potent SHIP
activator known to date. The third project studied the crystals of a novel eunicellin-based
diterpenoid (4.39) with a modest SHIP activity from an unidentified Micronesian soft coral RJA
47686. The X-ray analysis illustrated that the crystals are monoclinic, space group P21/b, with a
= 9.3711(14) A; α = 90⁰; b = 13.5349(17) A; β = 99.142(7)⁰; c = 10.9891(17) A; γ = 90⁰; V =
1376.1 (3) ų; Z value = 2; Dcalc 1.189. 10-³ g/cm³; F₀₀₀ 536.00; Cu (MoKα) 0.84 cm-¹.
Based on the NMR and x–ray data 4.39 was shown to possess (1R*, 2R*, 3R*, 6R*, 7S*, 10R*,
14R*, 18R*)-configuration with an ether linkage connecting C2 and C6.
9
Tabudravu, Jioji N. "Investigations of secondary metabolites from Fijian marine sponges." Thesis, University of Aberdeen, 2001. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602042.
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The following thesis presents results from investigations of marine natural products. It is divided into 7 chapters consisting of an introduction, five chapters examining the metabolites from Fijian marine sponges and one chapter examining the secondary metabolites from the medicinal plant, kava {Piper methysticum). Two new psammaplins (psammaplin K and L), a new isomalabaricane triterpene monosaccharide, two new bromotyrosine alkaloids (purealidin S and purpureamine J) and two new cyclic peptides (axinellin C and wainunuamide), a new conformer of phakellistatin 2 together with other known secondary metabolites were isolated from marine sponges. The new conformer of phakellistatin 2 was observed to adopt another conformation in CDCI3. Psammaplin A was found to inhibit chitinase from a Bacillus sp. and Serratia marcescens. The mode of activity was investigated by enzyme reaction kinetics and supported by X-ray crystallography. A new isomer of flavokavain A, woflavokavain A was isolated from kava, together with 7 known compounds. Solution conformations of axinellin C, jasplakinolide, phakellistatin 2 and its two conformers were generated using nOe restrained molecular modelling techniques.
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Drainville-Higgins, Katherine Evelyn. "Isolation of marine metabolites from S̲y̲m̲b̲i̲o̲d̲i̲n̲i̲u̲m̲ species of dinoflagellates /." View online ; access limited to URI, 2004. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3135901.
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Ayer, Stephen William. "Novel secondary metabolites from selected British Columbian marine invertebrates." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25557.
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Marine organisms show potential as sources for novel, biologically and pharmacologically active, secondary metabolites. Examination of three nudibranch and one bryozoan species for biologically active metabolites has led to the isolation and structural elucidation of nine new and two known secondary metabolites. The structures of all the compounds were determined by using a combination of spectral analysis, chemical interconversion, synthesis, and single-crystal X-ray diffraction analysis.
The British Columbian dorid nudibranch Acanthodoris nanaimoensis yielded three new sesquiterpenoids. The structures
of nanaimoal (61) , acanthodoral (64) , and isoacanthodoral (65) represent novel sesquiterpenoid carbon skeletons. The natural mixture of aldehydes 61, 64, and 65 exhibited antibacterial and antifungal activity. From Aldisa cooperi, two ∆⁴-3-ketosteroidal acids 23 and 24, and glycerol ether 25 were isolated. Acid 23 showed feeding deterrent activity against fish. The dendronotid nudibranch Meli be leonina gave 2,6-dimethy1-5-heptenal 53 and 2,6-dimethyl-5-heptenoic acid 54. The aldehyde 53 was responsible for the "grapefruit like" odour of the nudibranch. The bryozoan Phidolopora pacifica was examined in an attempt to correlate the absence of surface fouling, in the field, with the presence of biologically active secondary metabolites. The purine alkaloids 179 and 180, which contain the rare naturally occurring nitro functionality, were responsible for much of the antifungal and antialgal activity of the crude extracts. Three nitrophenols 181, 189, and 209 were also isolated from P. pacifica. Nitrophenol 181 had been previously shown to inhibit chloroplast development both in green plants and in the unicellular algae Euglena sp.Science, Faculty of
Chemistry, Department of
Graduate
12
Fahy, Eoin. "Polyketide derived metabolites from the marine hydroid Garveia annulata." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/27071.
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The marine hydroid Garveia annulata is a small, brightly colored coelenterate whose crude methanol extracts exhibit potent antibacterial and antifungal activity. The compounds responsible for this biological activity were purified and characterised as a series of related 1-[4H]-anthracenone derivatives. Twenty one metabolites have been isolated and their structures were elucidated by using a combination of spectral analysis, chemical interconversions, synthesis and single crystal X-ray diffraction analysis.
The structure of garveatin A (77), the major metabolite, was determined via a series of NMR experiments and by an X-ray diffraction analysis of its enol triacetate 87. Garveatins B (88), C (93) and D (96) share a common carbon skeleton with 77.
The garvin family represents a different polyketide folding pattern as seen in garvin A (124) and garvin B (126.) which contain an n-propyl group and a delta lactone functionality, respectively. Both the garveatins and the garvins contain oxidized analogs in the form of 2-hydroxy derivatives, 9,10 quinones and C2,2' dimers. NMR analysis and optical rotation experiments indicate that the C2 position of the 2-hydroxy compounds is racemic.
Garvalones A (137) and B (141) represent the corresponding 2-(3-oxobutyl) derivatives of garvins A and B respectively. They occur as pairs of C2 epimers. Their structures were confirmed by spectral comparison with 2-(3-oxobutyl) garveatin A (140) which was synthesised from 77.
Annulins A (144) and B (148) have degraded anthracene skeletons and they appear to be products of garveatin B metabolism.
All four families of G. annulata secondary metabolites appear to be produced by straightforward polyketide biogenesis. Different folding patterns of a putative nonaketide precursor account for all the structures elaborated. These polyketides represent the first examples of this type of metabolism in coelenterates.Science, Faculty of
Chemistry, Department of
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13
Williams, David Ellis. "Novel secondary metabolites from selected cold water marine invertebrates." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/29175.
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A study of the secondary metabolism of two nudibranchs and one soft coral has led to the isolation of eighteen new and two known secondary metabolites. The structures of all compounds were determined by a combination of the interpretation of spectral data, chemical degradations and interconversions, and single crystal x-ray diffraction analysis.
The British Columbian dorid nudibranch Diaulula sandiegensis yielded two new steroidal metabolites, diaulusterols A (41) and B (42). The 25-(3-hydroxybutanoate) residue of diaulusterol A (41) and the 2α,3α-diol array of both 41 and 42 are not commonly encountered in naturally occurring steroids. Both metabolites exhibited considerable antibacterial and antifungal activity. Steroid 41 exhibited fish antifeedant activity. The relative concentration of 4.1 and 42 in the skin extracts of D. sandiegensis appears to be related to the animals' seasonal abundance.
Extracts of the British Columbian soft coral Gersemia rubiformis yielded a series of ten diterpenes possessing cembrane (170-175), pseudopterane (167-169) and gersolane (176) carbon skeletons. The structure of an eleventh diterpene remains unresolved. In addition, the structure of a degraded diterpene possessing a 13-membered ring (177) is tentatively proposed. G. rubiformis represents the first example of a soft coral to yield pseudopterane diterpenes. The organism is the first to contain cembrane, pseudopterane and gersolane metabolites, a fact which has biogenetic implications. Two new sesquiterpenes were also isolated. Tochuinyl acetate (165) and dihydrotochuinyl acetate (166) represent the first examples of cuparane sesquiterpenes to be isolated from a soft coral. A biogenesis is proposed. Metabolite 166 exhibited fish antifeedant activity.
Investigations of Gersemia rubiformis collected in Newfoundland waters revealed that the secondary metabolism differed from west coast specimens. The isolation of the new unstable sesquiterpene (+)-β-cubebene-3-acetate (178) resulted.
Skin extracts of the dendronotoid nudibranch Toquina tetraquetra were examined in an attempt to correlate its feeding dependency and lack of predation to the presence of allomones. Metabolites 165, 166, 170, 179 and the new butanoate diterpene 180 could be traced to the coelenterates which make up the animal's diet. Tochuinyl acetate (165), dihydrotochuinyl acetate (166) and rubifolide (170) were previously found in extracts of Gersemia rubiformis. Ptilosarcenone (179) has been reported as one of the major metabolites of the sea pen Ptilosarcus
gurneyi²¹³. The exact origin of a sixth metabolite, pukalide (63), remains unknown. It is proposed that Tochuina tetraquetra selectively sequesters dietary metabolites for defensive purposes.Science, Faculty of
Chemistry, Department of
Graduate
14
Northcote, Peter T. "Novel terpenoid metabolites from the marine sponge xestopongia vanilla." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/29253.
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A chemical study of the marine petrosid sponge Xestospongia vanilla has led to the isolation of nine new isoprene derived secondary metabolites. Their proposed structures were elucidated by a combination of spectroscopic analysis and chemical degradation and interconversions.
Xestodiol (94), a C₁₈ apocarotenoid, appears to be a degradation product of the abundant marine carotenoid fucoxanthin (103). The xestovanins (98-102) are triterpene glycosides; their isolation represents the second reported occurrence of this type of compound from sponges. Their triterpene carbon skeletons are unique, and are either monocyclic (secoxestovanane skeleton) or bicyclic (xestovanane skeleton). All the xestovanins contain the same disaccharide fragment composed of L-rhamnose alpha linked to the 4 position of D-fucose. The fucose residue is beta linked to the same position on the aglycone in all isolated xestovanins. Xestovanin D (102) contains an extra L-rhamnose residue attached to a different position on the aglycone. Xestovanin A (98) was found to be an inhibitor of fungal growth, while xestovanin C (101) inhibited the growth of bacteria. A series of three smaller apparently related terpenes was also isolated. Xestenone (95) and secoxestenone (97) both contained new C₁₉ carbon skeletons. Secoxestenone (97), a monocyclic compound, could be converted into the bicyclic xestenone (95) by an intramolecular aldol condensation. The C₂₀ xestolide (96), with a similar structure to both xestenone and secoxestenone, had an unique carbon skeleton that could not be derived readily from an unrearranged diterpene skeleton. It is suggested that these three smaller terpenes (95-97) are degraded triterpenes, derived from a secoxestovanane carbon skeleton. The secondary metabolite chemistry of the petrosid sponges is reviewed, and an overview of triterpenes of marine origin is presented.Science, Faculty of
Chemistry, Department of
Graduate
15
Rateb, Mostafa Ezzat M. "Bioactive secondary metabolites from marine and under explored habitats." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=167782.
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This thesis presents results obtained from the investigation of secondary metabolites through screening of marine organisms, marine-derived microbes, and microbes form under-explored habitats. The first part includes the isolation of eight cytotoxic diterpene derivatives of which four were new from the organic extract of the sponge Spongionella sp. obtained from the U.S. National Cancer Institute’s Open Repository Program, the isolation of three new antibacterial dibenzofuran derivatives and a known butyrolactone from ascomycete Super1F1-09 isolated from the Indo-Pacific sponge Acanthella cavernosa. An attempt to synthesize these compounds was conducted. This part also includes the isolation of five known pyrroloiminoquinone alkaloids, from the Fijian sponge Zyzzya sp., which showed potent antiprotozoal activity. The second part comprises the use of OSMAC approach for the isolation of four new ansamycin-type polyketides, three new macrolactones and one known siderophore from Streptomyces strain C34 isolated from Atacama Desert, Chile. These compounds showed good antibacterial activity with one of the ansamycins showed pronounced antibacterial activity against a panel of clinical isolates of methicillin-sensitive as well as methicillin-resistant S. aureus (MRSA). This part also contains the use of microbial co-culture for the induction of secondary metabolites. It comprises the isolation of ten antiprotozoal fungal metabolites, of which one was new, from Aspergillus fumigatus when co-cultured with the novel strain Streptomyces C2 isolated from Atacama Desert. In conclusion, natural products from diverse sources proved to be the major resource of drug discovery. This thesis describes the isolation and structural characterisation of 35 compounds, 15 of which were new. Extremophiles proved to be a good source for new secondary metabolites.
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Antunes, Edith Martins. "Pyrroloiminoquinone metabolites from South African Latrunculid sponges." Thesis, Rhodes University, 2003. http://eprints.ru.ac.za/215/.
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Collett, Lynne Alison. "Structural and stereochemical investigations of terrestrial and marine pyrone metabolites." Thesis, Rhodes University, 1997. http://hdl.handle.net/10962/d1005013.
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This thesis presents an investigation into the chemistry of 6 substituted 5, 6-dihydro-a-pyrone compounds. A comprehensive review of these compounds was published in 1989 and the subsequent literature is covered in an updated review presented below. Eight 6-substituted 5,6-dihydro-a-pyrone metabolites from three different South African plant species Cryptocarya latijolia, Syncolostemon densiflorus, and Syncolostemon argenteus have been the subject of structural and stereochemical investigations. The absolute stereochemistry of the known compound "triacetate" from C. latijolia has been established as 6R-[2R,4S,6S-(triacetyloxy)heptylJ-5,6-dihydro-2H-pyran-2-one (74) using CD and acetonide formation with subsequent application of the modified Moshers method. The absolute stereochemistry of the related metabolite "diacetate", also from C. latijolia, has been assigned as 6R-[2S,4S-diacetyloxypentylJ-5,6-dihydro-2H-pyran-2-one (76). In addition, the outstanding stereochemistry at C-5' in syndenolide, from S. densiflorus, followed from conversion to its diacetonide and subsequent NMR analysis. Syndenolide is therefore 6R-[5S-(acetoxy)-IR,2R,3S-(trihydroxy)-heptylJ-5,6- dihydro-2H -pyran-2-one. The genus Syncolostemon has proved to be a rich source of a-pyrone compounds and the chemistry of S. argenteus, not investigated previously, was examined as part of an ongoing search for new 5,6-dihydro-a-pyrones. The study yielded five new a-pyrone natural products, synargentolide A-E. The structure of synargentolide A (82) has been assigned as 6R[4R,5R,6S-triacetyloxy-lE-heptenylJ-5,6-dihydro-2H-pyran-2-one using CD and NMR techniques. The structures of synargentolide B (87), C (92) and E (94) also followed from a detailed NMR analysis and the stereochemistry tentatively assigned based on CD and NMR data. Synargentolide D (93) was thermally unstable, and a paucity of material prevented stereochemical investigations, however the structure was determined from initial NMR analysis. The marine molluscs of the genus Siphonaria have only become the subject of chemical studies in the last fifteen years. These molluscs characteristically produce polypropionate type natural products. A review of Siphonarian polypropionate metabolites containing a pyrone functionality is presented. Examination of an endemic South African species Siphonaria serrata yielded one novel polypropionate metabolite containing a ),-pyrone functionality, siserrone A (131). The structure of this compound was unambiguously established using standard NMR experiments. The relative stereochemisty of the hemi-ketal moiety was assigned from a careful analysis of the ROESY NMR spectrum and the stereochemisty of the acyclic portion determined from a comparison of the 13C and 'H NMR data of a degradation product with the corresponding data of a synthetic compound. It was also established that the modified Moshers method could not be used to determine the absolute stereochemistry of the secondary hydroxy I substituent at C-11. The absolute stereochemistry of 131 was thus assigned in accordance with the proven stereochemistry of Siphonarian metabolites.
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Mkwananzi, Henry Bayanda. "A study of plocamium corallorhiza secondary metabolites and their biological activity." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1007666.
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Seaweeds of the genus Plocamium are known to produce a variety of halogenated monoterpenes. In addition to their ecological role as feeding deterrents, biological activities reported for these compounds include antibacterial, antialgal, antifungal and anticancer activities. An investigation of the non-polar extracts of the seaweed Plocamium corallorhiza resulted in the isolation of six known halogenated monoterpene compounds, 4-bromo-5-bromomethyl-1-chlorovinyl-2, 5-dichloro-methylcyclohexane (2.68), 1,4,8-tribromo-3 ,7-dichloro-3, 7-dimethyl-1,5-octadiene (2.67), 8-bromo-1 ,3,4,7-tetrachloro-3, 7-dimethyl-1,5-octadiene (2.66), 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2,7-octadiene (2.64), 4,8-dibromo-1,1,7-trichloro-3,7-dimethyl-2,5-octadiene (2.65) and 3,4 ,6,7-tetrachloro-3, 7-dimethyl-1-octene (2.63) as well as eight new compounds, including five halogenated monoterpene aldehydes. The new compounds were identified by 1D and 2D NMR spectroscopic techniques as: 8-Bromo-6,7-dichloro-3,7-dimethyl-octa-2,4-dienal (2.72), 8-Bromo-1,1,2,7-tetrachloro-3,7-dimethyl-octa-3,5-diene (2.70), 4,8-Dichloro-3,7-dimethyl-octa-2,4,6-trienal (2.74), 4-Bromo-8-chloro-3, 7-di methyl-octa-2, 6-dienal (2 76), 8-Bromo-4-chloro-3, 7-dimethyl-octa-2,4 ,6-trienaI (2.75), 4-Bromo-1,3,6,7-tetrachloro-3 ,7-dimethyl-octa-1,4-diene (2.71), 8-Bromo-1,3,4,7-tetrachloro-3,7-dimethyl-octa-1,5-diene (2.69), 4,6-Dibromo-3,7 -dimethyl-octa-2,7-dienal (2.73). All compounds were screened for antimicrobial activity, brine shrimp lethality and cytotoxicity towards oesophageal cancer cells. Compound 2.68 was toxic to brine shrimp larvae at a concentration of 50 μ/mL. It also showed promising activity towards oesophageal cancer cells with an IC₅₀, of 2 μg/mL.
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Van, Wyk Albert Wynand Wincke. "Studies in marine diterpene chemistry." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005019.
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This thesis comprises both a natural product investigation and a synthetic component. The natural product investigations are presented in Chapters Two and Three. In Chapter Two the isolation and spectroscopic identification of the new isocopalane diterpene 12S,13R,14Sisocopalan- 13-ol-12,14-diacetate (2.1) and two known 3-(14S)-isocopal-12-ene-15-oyl-1- acetyl-sn-glycerol (2.2) and 3-(14S)-isocopal-12-ene-15-oyl-2-acetyl-sn-glycerol (2.3) from a single, large, unidentified sub-Antarctic nudibranch, collected near Marion Island, approximately 2000 km south of Cape Town are described. Chapter Three discusses the isolation, spectroscopic structure elucidation and anti-oesophageal cancer activity (3.1-3.4 only) of two known labdane diterpenes 6β,7α-diacetoxylabda-8,13E-dien-15-ol (3.1) and 2α,6β,7α-triacetoxylabda-8,13E-dien-15-ol (3.2) and one new 6β,7α,15-triacetoxylabda 8,13E-diene (3.3), as well as new 3α,11-dihydroxy-9,11-seco-cholest-4,7-dien-6,9-dione (3.4) and cholest 7-en-3,5,7-triol (3.5) from the endemic pulmonate mollusc, Trimusculus costatus. The absolute configuration of 3.2, and hence 3.1 and 3.3 (from biogenetic arguments) was determined through X-ray diffraction of a single crystal of the camphanate ester of 3.2. The absolute configuration of the secondary hydroxyl at C-3 of 3.4 was established using the Modified Mosher’s method. The synthetic component of the thesis commences in Chapter Four with the semi-synthesis of labdane diterpene nitriles 9α-cyano-15,16-epoxy-7β-hydroxylabda-13(16),14-dien-6-one (4.1), 9α-cyano-15,16-epoxy-7-hydroxylabda-7,13(16),14-trien-6-one (4.2) and 9α-cyano-15,16- epoxy-6β,7β dihydroxylabda-13(16),14-diene (4.3) from the terrestrial labdane diterpene, hispanolone (4.4). This work is an extension of previous synthetic studies directed towards the synthesis of T. costatus metabolites. Diterpenes 4.1-4.3 exhibited in planta activity against the economically important crop pathogens, Magnaporthea grisea and Puccinia recondita. Chapter Five describes the successful semi-synthesis of two isomeric marine molluscan labdane diterpene aldehyde metabolites, labd-13E-ene-8β-ol-15-al (5.1) and labd-13Z-ene- 8β-ol-15-al (5.2) from the commercially available, terrestrial plant derived, labdane diterpene manool (5.3). Diterpenes 5.1 and 5.2, originally isolated from the Mediterranean nudibranch,Pleurobranchaea meckelii and selected diterpenes arising from this synthesis were evaluated for their activity against an oesophageal cancer cell line (WHCO1). Chapter Six further develops the research discussed in Chapter Five, where ethyl 17-norabiet-13(15)-E-en-8β-ol- 16-oate (5.49) and ethyl 17-norabiet-13(15)-Z-en-8β-ol-16-oate (5.50) were first semisynthesized serendipitously. Based on their structural relationship to naturally occurring tricyclic diterpenes with anti-plasmodial activity, tricyclic diterpenes, 17-norpimaran-13α- ethoxy-8,16-olactone (6.6), 17-norisopimar-15-ene-8β,13β-diol (6.7), 17-norisopimarane- 8β,16-diol (6.8) and 17-norabiet-13(15)-ene-8β,16-diol (6.9) were semi-synthesized from the terrestrial labdane diterpene, 5.3, and critically evaluated for their antimalarial potential from parasite inhibition and haemolytic studies.
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Gerard, Jeffery M. "Antibiotic secondary metabolites of bacteria isolated from the marine environment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25055.pdf.
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Kyeremeh, Kwaku. "Metal complexation, spectroscopic and electrochemical properties of marine secondary metabolites." Thesis, University of Aberdeen, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439964.
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The metal binding properties of the marine pyridoacridine alkaloid ascididemin was studied with a wide range of spectroscopic and spectrometric techniques. MSn electrospray ionization mass spectrometry showed that ascididemin binds Cu2+ and forms either 2 : 1 or 1 : 1 complexes depending on the concentration of the metal ion. Analysis of the MSn results showed that there is the possibility of a one electron reduction of Cu2+ to Cu+ on complexation to ascididemin. It was hypothesised that this one electron transfer was dependent on the type of salvation ligands present after ascididemin forms a complex with the metal ion. It looks as if ligands like C1-, OH- and CH3COO- do not favour the one electron transfer from ascididemin to copper and hence complexes solvated by these ligands have copper in the +2 oxidation state. Neutral ligands like H2O and CH3OH favour the one electron transfer and complexes solvated by these ligands have copper in the +1 oxidation state. Complexes between ascididemin and copper which were detected in MSn with no ligands of salvation had copper in the +1 oxidation state. UV results showed multiple isosbestic points for the gradual formation of the 2 (ascididemin) : (copper) complex when increasing concentrations of the metal ion (0-1 equivalents) were added to 2 equivalents of ascididemin. The fluorescence of ascididemin is quenched by the metal ions Cu2+, Co2+ and Ni2+ in a concentration dependent manner. However, Zn2+ does not quench the fluorescence of ascididemin which led to the suspicion that the metal does not form complexes with ascididemin. Detailed fluorescence spectroscopy studies revealed that Cu2+ is capable of competing out (binds preferentially) Co2+ and Ni2+ in binary solutions containing copper and either of the metals. In more complex mixtures simulated by a combination of all four metal ions (Cu2+, Co2+, Ni2+ and Zn2+) it seemed as if the effect of copper is not obvious at very low concentrations (10-9 -10-15 M). However, at higher concentrations (10-6 M or higher) copper is able to compete out all the three metals and the use of ascididemin as a chemosensor for copper is possible in this concentration region. Cyclic voltammetry studies showed that the formation of complexes between ascididemin and the divalent metal ions is able to decrease the amount of current formed (Ipc) at the glassy carbon electrode by reduction of Cu2+ to Cu+. This effect was attributed to either a decrease in the diffusion rates of mass transport for the complexes relative to the metal ions or a decrease in the concentration of the metal ion Cu2+ due to ascididemin complexation.
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Kottakota, Suresh Kumar. "The synthesis of novel biologically active marine sponge secondary metabolites." Thesis, University of Sunderland, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.592881.
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Bromotyrosine-derived secondary metabolites from marine sponges of the order Verongida provide unique diversity in chemical structure and a wide range of biological activities. With a decline in the number of novel antibiotic scaffolds which are emerging and the on-going search for more effective antibacterial and anticancer drugs, these brominated metabolites are attractive candidates for further total synthesis and biological evaluation. An Efficient total synthesis of bromotyrosine alkaloids purpurealdin E (92), aplyzanzine A (122), suberedamine A (123) and B (124), iso-Anomoian A (121a) and aplysamine-2 (104) were achieved through the carbodiimide coupling of appropriate tyrosine/tyramine units in excellent yields. Their structures have been confirmed through direct comparison with spectroscopic data of isolated natural products. The key step was the one-pot Bocdeprotection, dimethylation and hydrolysis of desired intermediate, which was achieved in 88% yield. A new synthetic route was developed for the preparation of diverse analogues for biological assessment. This route utilized cheap and commercially available starting materials, and allowed access to various analogues inaccessible via currently reported methods. By utilising this route, the total syntheses of 5- bromoverongamine (207), 20-N-methylpu rpuramine E (208) , psammaplin A (150), psammaplin C (156), spermatinamine (50) and tokaradine A (209) were successfully carried out and are reported herein. These new syntheses of spermatinamine and psammaplin A are more efficient than previously reported sequences. In addition, we explored a method for the selective removal of benzyl protecting groups in the presence of both oxime and disulphide moieties. Aplyzanzine A (122) was found to be the most active product against a Grampositive bacterial and fungal screen demonstrating MIC values 2-4 times lower than the other compounds. All compounds, except purpurealdin E and psammaplin C, exhibit modest inhibition against M. bovis BCG and M. tuberculosis H37Rv. 20-N-methylpurpuramine-E (208) was most active with an MIC (5 μg/mL) towards M. bovis BCG. iso-Anomoian A (1 21a) and suberedamine B (124) showed antitumor activity in the NCI-DTP60 cell line screen at single micromolar concentrations, with iso-anomoian A (121 a) inhibiting 53 cell lines. These molecules present novel scaffolds for further optimization.
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Mann, Maryssa Gudrun Ailsa. "An investigation of the antimicrobial and antifouling properties of marine algal metabolites." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1007465.
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Prevention of the accumulation of undesirable biological material i.e. biofouling upon a solid surface requires the use of antifouling systems. The solid surface may be a contact lens, an off shore oil rig or a living organism. When chemicals are employed as a mechanism of defense against biofouling, the agents involved are known as antifouling agents. Marine algae must protect themselves from fouling organisms and it is thought that one of the mechanisms used by these organisms is the production of secondary metabolites with an array of biological activities. In vitro studies have shown numerous compounds isolated from marine algae to possess antibacterial, antifungal and antimacrofouling activity. The aim of this study was to evaluate the secondary metabolite extracts of selected Southern African marine macro-algae as a potential source of compounds that inhibit biofilm formation and that could be used as antifouling agents. In this project, marine macro-algae were collected from various sites along the South African coastline. Their extracts were screened for antimicrobial activity against four ubiquitous microorganisms, Staphylococcus aureus, Klebsiella pneumoniae, Mycobacterium aurm and Candida albicans. Results of screening assays guided the fractionation of two Rhodophyta, Plocamium corallorhiza and Laurencia flexuosa. The algae were fractionated using silica gel column chromatography and compounds were isolated by semi-preparative normal phase HPLC. Compound characterization was performed using UV, IR and advanced one- and two-dimensional NMR (¹H, ¹³C NMR, COSY, HSQC, HMBC and NOESY) spectroscopy and mass spectrometry. Ten halogenated monoterpenes including four members of the small class of halogenated monoterpene aldehydes were isolated from extracts of P. corallorhiza. The compounds isolated included the known compounds 3,4,6,7-tetrachloro-3,7-dimethyl-1-octene; 4,6-dibromo-1, 1-dichloro-3,7 -dimethyl-2E,7 octadiene; 4,8-d ibromo-1,1,7 -trichloro-3, 7-dimethyl-2,5Eoctadiene;1 ,4,8-tribromo-3, 7 -dichloro-3,7-dimethyl-1 E,5E-octadiene; 8-bremo-6, 7-dichloro-3,7-dimethyl-octa-2E,4E-dienal; 4-Bromo-8-chloro-3,7-dimethyl-octa-2E,6E-dienal; 4,6- Dibromo-3,7-dimethyl-octa-2E,7-dienal; 2,4-dichloro-1-(2-chlorovinyl)-1-methyl-5-methylidene-cyclohexane and two new metabolites 4,8-chloro-3,7-dimethyl-2Z,4,6Z-octatrien-1-al and Compound 3.47. Methodology was developed for the chemical derivatization and mass spectrometric analysis of the aldehydic compounds, The aldehyde trapping reagent 0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride was used to derivatize the molecules, stabilizing them and allowing for their complete characterization. From Laurencia flexuosa a new cuparene sesquiterpene 4-bremo-2-(5-hydroxy-1,2,2- trimethylcyclopent-3-enyl)-5-methylphenol was isolated along with two geometric isomers of the vinyl acetylene bromofucin , An halogenated monoterpene 3S*,4R*-1-bromo-3,4,8-trichloro-9-dichloromethyl-1-E,5-E,7-Z-octatriene was also isolated but was suspected to be a contaminant and an investigation into its biological source revealed that it originated from Plocamium suhrii. A third alga, Martensia elegans was extracted based on published reports of antimicrobial compounds in related species. A new a-alkyl malate derivative was isolated and characterized. Selected compounds isolated during the course of the study were employed in preliminary assays that tested their ability to inhibit biofilm formation by Pseudomonas aeruginosa. The halogenated monoterpenes isolated from the Plocamium species were the only active compounds. 3S*,4R*-1-bromo-3,4,S-trichloro-g-dichloromethyl-1-E,5-E,7-octatriene from P. suhrii inhibited biofilm formation through antibacterial activity on planktonic cells but could not prevent biofilm formation when employed as a film on the surface of microtitre plate wells. 1,4,8-tribromo-3,7-dichloro-3,7-dimethyl-1E,5E-octadiene and 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2E,7-octadiene inhibited biofilm formation when applied as a film to the microtitre plate wells but had no significant antibacterial activity. No potential antifouling agents were identified in this project but the antimicrobial activity exhibited by the crude algal extracts was highly encouraging and a number of new research areas have been identified.KMBT_363
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Egan, Suhelen Microbiology & Immunology UNSW. "Production and regulation of fouling inhibitory compounds by the marine bacterium Pseudoalteromonas tunicata." Awarded by:University of New South Wales. Microbiology and Immunology, 2001. http://handle.unsw.edu.au/1959.4/17838.
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The marine surface-associated bacterium Pseudoaltermonas tunicata, produces a range of compounds that inhibit fouling organisms, including invertebrate larvae, bacteria, algal spores and fungi. In addition to these antifouling compounds P. tunicata cells produce both a yellow and a purple pigment. The aim of this study was to further characterise the antifouling activities, their regulation and relationship with pigmentation, and the ecological significance of P. tunicata and related organisms. It was discovered that the anti-algal compound was extracellular, heat sensitive, polar and between 3 and 10 kDa in size. The anti-fungal compound was found to be the yellow pigment and active against a wide range of fungal and yeast isolates. Chemical analysis suggests that this compound consists of a carbon ring bound to a fatty-acid side chain. Genetic analysis supports the chemical data for the active compound as a mutant in a gene encoding for a long-chain fatty-acid CoA ligase was deficient for anti-fungal activity. To address the regulation of antifouling compounds and their relationship to pigmentation transposon mutagenesis of P. tunicata was performed. Mutants lacking the yellow pigment displayed a reduced ability to inhibit fouling organisms. Further analysis of these mutants identified genes involved with the synthesis and regulation of synthesis of pigment and antifouling compounds. One of these mutants was disrupted in a gene (wmpR) with similarity to the transcriptional regulators ToxR from Vibrio cholerae and CadC from Escherichia coli. Analysis of global protein expression using two-dimensional gel electrophoresis showed that WmpR is essential for the expression of at least fifteen proteins important for the synthesis of fouling inhibitors. The ecological significance of antifouling bacteria was addressed by assessing the antifouling capabilities of a collection of bacteria isolated from different marine surfaces. Overall, isolates from living surfaces displayed more antifouling traits then strains isolated from non-living surfaces. Five dark-pigmented strains originating from the alga Ulva lactuca were further studied. Phylogenetic and phenotypic analysis revealed that they were all members of the genus Pseudoalteromonas and were closely related to P. tunicata. Two strains represented a novel species within the genus and were taxonomically defined as P. ulvae sp. nov.
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Fakee, Jameel. "The isolation and characterisation of secondary metabolites from selected South African marine red algae (Rhodophyta)." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001472.
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Secondary metabolites from natural sources are fast growing as popular drug leads. The structural novelty and favourable biological activity that these compounds display contribute to their popularity as drugs of the future. Examples of such compounds include the potent anticancer drug paclitaxel isolated from the bark of a yew tree as well as the more commonly known analgesic aspirin which stems from the bark of the willow tree. The biological activities exhibited by these secondary metabolites are vast and range from antimicrobial to anticancer activity to mention but a few. As a result, the isolation of novel compounds from natural sources is on the rise. The South African seaboard is home to a wealth of various marine algal species which produce fascinating secondary metabolites. For example, Portierria hornemanii was shown to produce halomon, a halogenated monoterpene which has displayed promising cytotoxic activity. This study thus focused primarily on pursuing novel compounds from three endemic South African marine algal species which have never been analysed previously from a chemical perspective. These are Plocamium rigidum (Bory de Saint-Vincent), Laurencia natalensis (Kylin) and Delisea flaccida (Suhr) Papenfuss. Four known compounds and one new halogenated monoterpene, (2E,5E,7Z)-8-chloro- 7-(dichloromethyl)-4-hydroxy-3-methylocta-2,5,7-trienal, were isolated from Plocamium rigidum. The breast cancer (MCF-7 cell line) inhibitory activity for these compounds was assessed and it was observed that an increase in the lipophilic nature of the compounds produced more favourable IC50 values. A pre-cursor to bromofucin type compounds, cis-laurencenyne, was isolated from Laurencia natalensis, as well as a new acetoxy chamigrane type compound, 4-bromo- 3,10-dichloro-7-hydroxy-3,7,11,11-tetramethylspiro [6.6] undec-1-yl acetate. Delisea flaccida was seen to contain two known bromofuranone type compounds isolated as an isomeric mixture, 1-[(5Z)-4-bromo-5-(bromomethylidene)-2-oxo-2,5- dihydrofuran-3-yl] butyl acetate and 1-[(5E)-4-bromo-5-(bromomethylidene)-2- oxo-2,5-dihydrofuran-3-yl]butyl acetate. These compounds are famous for their ability to inhibit bacterial biofilm production and they have been isolated before from an Australian Delisea sppAdobe Acrobat 9.53 Paper Capture Plug-in
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Amiri, Moghaddam Jamshid [Verfasser]. "Genome mining of marine bacteria for bioactive metabolites / Jamshid Amiri Moghaddam." Bonn : Universitäts- und Landesbibliothek Bonn, 2019. http://d-nb.info/1181855918/34.
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Afolayan, Anthonia Folake. "Isolation and characterization of antiplasmodial metabolites from South African marine alga." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1003063.
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Malaria is one of the three most deadly diseases in Africa. Although there are available treatments, their efficacy has been greatly reduced over the past two decades due to the development of resistance to currently available drugs. This has necessitated the search for new and effective antimalarial agents. This project approached the search for new antimalarial compounds in two ways: (i) by screening natural products isolated from marine algae against the Plasmodium parasite and (ii) by modification of selected isolated active compounds to target 1-deoxY-đ-xylulose 5-phosphate reductoisomerase (DXR), an enzyme found in the nonmevalonate isoprenoid biosynthetic pathway of Plasmodium Jalciparum. It was envisaged that such a compound would exhibit dual action on the Plasmodium parasite. Extracts obtained from 22 marine algae were prefractionated by solvent partitioning and were screened for anti plasmodial activity against the chloroquine sensitive (CQS) P. Jalciparum D 10 strain. Overall, 50% of the algae screened produced at least one crude fraction with activity against P. Jalciparum. Extracts of the algae Sargassum heterophyllum, Plocamium cornutum, Amphiroa ephedrea and Pterosiphonia cloiophylla gave the most promising results. Fractionation of S. heterophyllum afforded three tetraprenyltoluquinols (3.1, 3.2 and 3.5) and an all-trans-fucoxanthin (3.6). Three new compounds (4.5, 4.6 and 4.7) and two known halogenated monoterpenes (4.1 and 4.4) were isolated from P. cornutum. Each of the isolated compounds from both S. heterophyllum and P. cornutum showed antiplasmodial activity with IC₅₀ values ranging from 2.0 - 15.3 μM for S. heterophyllum and 13 - 230 μM for P. cornutum. Attempts to synthetically modify halogenated monoterpene 4.4 by dihydroxylation and phosphorylation in order to inhibit the DXR enzyme was unsuccessful. However, the hemiterpene analogue (5.42) of the halogenated monoterpenes was successfully phosphorylated and dihydroxylated to give compound 5.45 which showed promising activity against DXR. The result obtained indicated that the proposed phosphorylation and dihydroxylation of the halogenated monoterpene 4.4 would result in the synthesis of a potent DXR inhibitor and therefore a potential antimalarial agent with dual mode of action on the Plasmodium parasite.
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Paul, Nicholas Andrew School of Biological Earth & Environmental Sciences UNSW. "The ecology of chemical defence in a filamentous marine red alga." Awarded by:University of New South Wales. School of Biological, Earth and Environmental Sciences, 2006. http://handle.unsw.edu.au/1959.4/24304.
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I investigated the ecological functions of halogenated secondary metabolites from the red alga Asparagopsis armata, their localisation in specialised cells and also their cost of production. A. armata produces large amounts of halogenated metabolites ( < 20 ??g / mg dry weight) that are sequestered in gland cells, as was demonstrated with light, epifluorescence and transmission electron microscopy. Cellular structures were identified that likely assist the release of metabolites from the gland cells to the algal surface. The halogenated metabolites of A. armata have multiple ecological roles, functioning as both inhibitors of bacterial fouling and as herbivore deterrents. Their activity against bacteria and herbivores was measured by a novel test in which the metabolites were manipulated in A. armata by omitting bromide ions from the culture media. This technique prevented the production of halogenated metabolites, but did not impact on other aspects of algal biology. Algae lacking halogenated metabolites (bromide [-] algae) had higher densities of epiphytic bacteria than those that continued to produce metabolites (bromide [+] algae). Bioassays with pure compounds against individual bacterial isolates further supported an inhibitory role for the halogenated metabolites against epiphytic bacteria, and also indicated an affect on bacterial community structure as well as abundance. Bromide (+) A. armata produced halogenated metabolites that also deterred feeding by two herbivores (an amphipod and an abalone), but not a third (an opisthobranch mollusc). A novel outcome from these feeding assays was the demonstration of a relationship between herbivore size and consumption of the chemically defended A. armata by the abalone Haliotis rubra. In addition to the fitness benefits gained from chemical defence, there were also costs for allocating resources to secondary metabolites. These costs were only detected under limiting light resources, consistent with predictions of the plant defence models. The integration of chemical analyses and cellular measures of chemical defence proved essential in elucidating resource allocation to chemical defence in the filamentous stage of A. armata. This thesis highlights that the simple relationships between growth and defence in filamentous algae can provide an excellent model for studies of the ecology and evolution of chemical defences in marine algae.
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Osterhage, Claudia. "Isolation, structure determination and biological activity assessment of secondary metabolites from marine-derived fungi." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962823368.
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Jenkins, Kelly Matthew. "Chemical investigations of marine filamentous and zoosporic fungi and studies in marine microbial chemical ecology /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9907830.
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Swasono, Respati Tri. "Bioactive secondary metabolites from Australian invertebrates, Indonesian marine sponges, and an Indonesian terrestrial plant /." [St. Lucia, Qld.], 2006. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19275.pdf.
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Oh, Dong-Chan. "New secondary metabolites from the marine actinomycete, Salinispora, and microbial co-cultures /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3236625.
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Kubanek, Julia Marie. "Chemical studies on the origin of secondary metabolites in selected marine invertebrates." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq27181.pdf.
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Roper, Kathrein Elizabeth. "Cellular and molecular targets of allelochemicals from marine sponges /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19101.pdf.
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Richardson, Daniel M. "The biological effects of polycyclic aromatic hydrocarbons in the Scottish marine environment." Thesis, Robert Gordon University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247488.
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Sunkel, Vanessa Ann. "The investigation of novel marine microorganisms for the production of biologically active metabolites." Thesis, Rhodes University, 2009. http://hdl.handle.net/10962/d1004579.
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New drugs, particularly antibiotics, are urgently required to combat the increasing problem of antibiotic resistant human pathogens. Due to the scarcity of products available today, the pharmaceutical industry is now under pressure to reassess compounds derived from plants, soil and marine organisms. Pharmaceutical companies are showing renewed interest in marine biotechnology as the oceans represent a rich source of both biological and chemical diversity of novel molecular structures with anti-cancer, anti-inflammatory and antibiotic properties. Formerly unexplored locations, such as deep ocean sediments, show great potential as a source of genetically novel microorganisms producing structurally unique secondary metabolites. In this research, a metabolite producing marine Pseudoalteromonas strain, known as AP5, was initially used to develop methods for the detection, optimisation of production and extraction of bioactive metabolites from other potentially novel marine isolates. Two hundred and seventy six (276) marine isolates from water and sediment samples from the Antarctic Ocean and Marion Island were isolated. Ten visually different isolates were screened for bioactivity against Gram-positive and -negative bacteria, fungi and yeast. Three out of the 10 isolates, WL61 , WL 114 and WL 136, appeared to be novel Streptomyces spp. showing activity against different test organisms. Many of these marine microorganisms are difficult to culture in the laboratory, particularly when they are cultivated continuously in shake flasks as they can stop producing bioactive compounds. The cultivation of marine isolates in bioreactors may be a more beneficial process for the optimisation of metabolite production compared to conventional liquid fermentation techniques whereby the solid-liquid-air interface of membrane bioreactors can imitate the natural environment of microbes. The membrane bioreactor system is a stable growth environment with low shear that supports steady-state biofilm growth consisting of a high cell density due to a high mass transfer of nutrients and oxygen to the cells. This approach was employed and isolates WL61, WL114 and WL136 were immobilised onto ceramic membranes using Quorus single fibre bioreactors (SFR). The SFRs were used to establish the most suitable growth medium for continuous secondary metabolite production. The best growth conditions were applied to the Quorus multifibre bioreactor (MFR) for scale up of biologically active metabolites, highlighting the potential of bioreactor technology for use in bioprospecting for isolating and screening novel and known organisms for new and interesting natural products. Furthermore, the Quorus MFR was shown to be suitable for the production of high yields of antimicrobial metabolites and is an efficient new fermentation production system. Purification by HPLC fractionation was used to characterise four major compounds from isolate WL 114 extracts. NMR structure elucidation identified one of the two primary compounds as Bisphenol A. The complete chemical structure for the second potent bioactive compound could not be determined due to the low concentration and volume of material.KMBT_363
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Lister, Troy, and mike perkins@flinders edu au. "Total Synthesis of Auripyrone A and Related Metabolites." Flinders University. School of Chemistry, Physics and Earth Sciences, 2006. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20060804.125858.
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In recent decades the emergence of marine polypropionate natural products as compounds of diverse structural complexity and intriguing biological activity has influenced the advancement of asymmetric synthesis and predicated detailed studies of marine ecology. The introductory chapter of this thesis explores the nature of marine natural products, including their structure, biological activity and biosynthesis. Additionally, a brief review of the aldol reaction is presented. This well established biomimetic chemical transformation underpins polyketide synthesis and was utilised extensively in the research contributing to this dissertation. Chapter Two describes the first asymmetric total synthesis of the two marine polypropionates isolated from specimens of Siphonaria australis by Hochlowski et al. in 1984. Spectroscopic analysis revealed hemiacetal 22 and ester 23 to be identical to the secondary metabolites extracted from the marine pulmonate. The synthetic approach to hemiacetal 22 utilised lactate derived ketone (S)-67 to control the configuration of the C7 and C8 stereocentres and involved the discovery of a mild protocol for the synthesis of trimethylsilyl enol ether 109, which was employed for a Mukaiyama aldol homologation reaction. Additionally, ester 23 was synthesised from hemiacetal 22 via a retro-Claisen fragmentation.
The retro-Claisen approach utilised in the synthesis of ester 23 was extended in Chapter Three to serve as the pivotal transformation in an attempted total synthesis of the unusual marine polypropionate dolabriferol (30). The strategy toward dolabriferol (30) involved an iterative homologation of chiral ketone (S)-67 to install all but one of the requisite stereocentres in the natural product. Chemoselective deprotection of acyclic precursor 160 gave the elaborate 2,4,6-trioxaadamantane 167, whose participation as a protecting group mimic lead to the formation of ester 169 after reaction of the polycycle 167 with base. The synthesis of ester 169, which represents a direct precursor to dolabriferol (30), was achieved in 16 steps with an overall yield of 24%. Unfortunately, a robust protecting group on ester 169 prohibited a synthesis of dolabriferol (30), but intriguingly in one deprotection of ester 169 with aqueous hydrofluoric acid, spiroacetal 172 was isolated.
Chapter Four describes the first total synthesis of cytotoxic marine polypropionate auripyrone A (78) and establishes the absolute configuration of this important natural product as that depicted for compound 78. The requisite C8-C12 stereopentad of auripyrone A (78) was formulated from Evans� dipropionate equivalent 53 in a double stereodifferentiating aldol reaction, followed by syn-reduction to give diol 206. Differentiation of the secondary alcohols in compound 206 was achieved by migration of the PMB protecting group and protection at C11 with the requisite acyloxy group of auripyrone A (78). Differential protection was critical to achieving selective spiroacetalisation to afford the unique spiroacetal dihydropyrone core of the natural product. The utility of LiHMDS for highly selective double stereodifferentiating aldol homologations of sensitive fragments is also discussed. This mild aldol protocol was pivotal to forming the carbogenic skeleton of auripyrone A, in particular, elaborate adduct 278.
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Matobole, Relebohile Matthew. "Matrix comparison of isolation conditions for secondary metabolite producing marine sponge associated bacteria." University of the Western Cape, 2015. http://hdl.handle.net/11394/4754.
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>Magister Scientiae - MScThe discovery of novel secondary metabolites has declined significantly in recent years whereas there is a rise in the number of multi-drug resistant pathogens and other types of diseases. The decline in natural product discovery was due to high rediscovery of already known compounds and the costs in developing natural products. As a result pharmaceutical companies lost interest in investing in natural product discovery. However, there is a renewed interest in marine sponge associated microorganisms as a rich and untapped source of secondary metabolites. The objective of this study was to design a matrix to investigate the extent to which the One Strain-Many Compounds (OSMAC) approach applies to a collection of marine sponge isolates harvested from two South African marine sponge samples. Terminal restriction fragment length polymorphisms (T-RFLP) analysis was used to investigate and ascertain the two marine sponges which hosted the highest microbial diversities to be used for further culture-dependent studies. The culture-dependent studies, using 33 media which included liquid enrichment, heat treatments and antibiotic treatments, resulted in 400 sponge isolates from the two marine sponges Isodictya compressa and Higginsia bidentifera. Using antibacterial overlay assays, 31 dereplicated isolates showed antibacterial activity. Bioactivities were also exhibited against E. coli 1699 which is genetically engineered for resistance against 52 antibiotics which implies that some of the bioactive compounds could be novel. The 16S rRNA gene sequences revealed that the microbial phyla isolated from the marine sponges belonged to Actinobacteria, Firmicutes and Proteobacteria (Alphaproteobacteria and Gammaproteobacteria).Thirty isolates were selected for an OSMAC-based matrix study, 17 of which showed noantibacterial activities in preliminary screening. The application of the OSMAC approach using co-culture and 36 culture conditions resulted in 6 isolates showing antibacterial activities, three of which did not show activities in preliminary screening. One of these, a Bacillus pumilus isolated from I. compressa displayed antibacterial activity against 5 indicator strains whereas in preliminary screening it had not shown activity. The results show that marine sponges can host novel microbial species which may produce novel bioactive compounds. The results also confirm that traditional methods employing a single culture condition restricts the expression of some biosynthetic pathways of microorganisms and as a result many metabolites have yet to be identified.
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Till, Marisa. "Studies of New Zealand Marine Organisms." The University of Waikato, 2007. http://hdl.handle.net/10289/2498.
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The chemical study of three New Zealand marine organisms is described, along with a survey of the chemistry and biological activity of eighty-five marine organisms collected from New Zealand waters. The study of the New Zealand marine bryozoan Pterocella vesiculosa has resulted in the isolation of three new compounds; pterocellin H, pterocellin I and 1-methyl-5-bromo-8-methoxy-β-carboline. These compounds were characterised using high resolution mass spectrometry, one- and two-dimensional nuclear magnetic resonance spectroscopy and X-ray crystallography. The biological activity of these compounds was investigated and a discussion of the results including a comparison with the activity of closely related compounds is also presented. The crude extracts of eighty-five marine organisms were surveyed to establish their biological activity and chemical constituents. The results of this study indicated which species had interesting biological activity. The chemical survey allowed geographical and intra-species comparisons of chemical constituents between samples, as well as potentially indicating the presence of known secondary metabolites. For the Pterocella vesiculosa samples the survey methodology clearly illustrated the presence of pterocellins A and B. Two marine organisms were chosen for further investigation based on their biological activity and chemical survey results. Bioactivity directed isolation procedures yielded no new compounds from the organisms. The sterol composition of these species is also presented.
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Dávila, Céspedes Antonio [Verfasser]. "Metabolites of bacteria isolated from marine environments: chemistry and bioactivities / Antonio Dávila Céspedes." Bonn : Universitäts- und Landesbibliothek Bonn, 2018. http://d-nb.info/119893333X/34.
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Daletos, Georgios [Verfasser]. "Isolation and Structure Elucidation of Bioactive Secondary Metabolites from Marine Sponges / Georgios Daletos." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2016. http://d-nb.info/1101693908/34.
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Scheepers, Brent Ashley. "Synthesis of triprenylated toluquinone and toluhydroquinone metabolites from a marine-derived Penicillium fungus." Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1005038.
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This project forms part of a collaborative effort between the marine natural products chemists at Rhodes University and the medical biochemists at the University of Cape Town’s School of Medicine. Our UCT collaborators tested the cytotoxicity of a group of toluhydroquinones and toluquinones (9-15) against the oesophageal cancer cell line WHCO1 and revealed that the triprenylated toluhydroquinone 11 and it’s oxidised analogue 12 were the most active. This thesis presents an investigation into the role of the polyprenyl side-chain in the cytotoxicity of compound 11 and it’s oxidised analogue 12 by synthesizing and testing the cytotoxicity of simplified analogues of this compound. The synthesis of the two ortho-prenylated toluhydroquinone analogues 5-methyl-2-[(2'E,6'E)-3',7' -dimethyl-2',6'-octadienyl]-1,4-benzenediol (19) and 5-methyl-2-[(2'E,6'E)-3',7',11'-trimethyl-2',6',10'-dodecatrienyl]-1,4-benzenediol (21) and their two ortho-prenylated toluquinone analogues, 5-methyl-2-[(2'E,6'E)-3',7'-dimethyl-2',6'-octadienyl]-2,5-cyclohexadiene-1,4-dione (20) and 5-methyl-2-[(2'E,6'E)-3',7',11'-trimethyl-2',6',10'-dodecatrienyl]-2,5-cyclohexadiene-1,4-dione (22) is described. Our initial attempts to couple geranyl bromide, farnesyl bromide and farnesal to the aromatic precursors m-cresol and 1,4-dimethoxy-2-methylbenzene using directed ortho-prenylation and phenoxide carbon-alkylation were unsuccessful. The four target analogues were eventually synthesized via the initial metal halogen exchange reaction between 1-bromo-2,5-dimethoxy-4-methylbenzene and geranyl bromide/farnesyl bromide using n-BuLi and TMEDA in ditheyl ether at 0 °C to yield 92 and 104 respectively in moderate yield. The demethylation of both compounds preceded smoothly using AgO giving the target analogues 20 and 22 in good yield (approx. 90 %). The reduction of quinones 20 and 22 with sodium dithionite gave 19 and 21 in quantitative yield. The synthesis reported here is the first regioselective synthesis of these compounds. The anti-oesophageal cancer activity of 19-22 and two commercially available non-prenylated analogues 17 and 18 were tested against WHCO1. The conclusion drawn from the anti-oesophageal cancer study was that the polyprenyl side-chain plays a negligable role in the cytotoxicity of compounds such as 11 and 9 against the oesophageal cancer cell line WHCO1.
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Wegerski, Christopher John. "Chemistry under the sea : secondary metabolites from marine sponges of Papua New Guinea /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.
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Chow, Sharon. "Studies towards the total syntheses of natural metabolites isolated from insects and a marine alga /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18056.pdf.
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Ross, Andrew R. "Studies towards the synthesis of Popolohuanone E." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388550.
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Zang, Qin. "Towards the total synthesis of peloruside A analogues." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1663059931&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Critcher, Douglas James. "The total synthesis of neohalicholactone." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296300.
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Boonlarppradab, Chollaratt. "Investigation of the potential anticancer and antifungal active secondary metabolites from marine natural products." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3274752.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed October 5, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Hassouna, Dina [Verfasser], Peter [Akademischer Betreuer] Proksch, and Matthias [Gutachter] Kassack. "Secondary Metabolites of Marine-Derived Fungi / Dina Hassouna ; Gutachter: Matthias Kassack ; Betreuer: Peter Proksch." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2021. http://d-nb.info/1231075139/34.
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Abualreesh, Heba. "Screening for antibacterial metabolites in marine sponges collected from the coastline of Sri Lanka." Thesis, Uppsala universitet, Farmakognosi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-451690.
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Natural products and their derivatives have and are still used by humans for various health ailments due to their rich sources of drug discovery. New biologically active compounds from natural products play a key role in drug development. Marine sponges and their associated microbes contain a lot of bioactive compounds that are potential for drug development. These compounds produce chemical compounds with useful pharmaceutical properties such as antitumor, anti-infective, anti-inflammatory, and antibacterial properties. The main focus of this project was on the antibacterial activity of six different sponge specimens. The aim was to screen the antibacterial activity of the sponge specimen’s extracts. In order to do so, a Minimum Inhibitory Concentration assay was performed to screen the sponge's antibacterial activity against E. coli and S. aureus. Analytical HPLC was used for separation and Solid Phase Extraction (SPE) was used for determining the effect of salts towards the inhibition of anti-bacterial activity for two selected extracts. Ethanolic extract of Stylissa massa showed antibacterial activity against S. aureus. SPE would be a rapid purification step to remove the salts present in sponges at a high concentration but it has not shown a significant effect on the inhibition of antibacterial activity. However, further separation and purification need to be done to be able to completely screen for all the six different sponge specimens.