| The marine environment has proven to be an excellent source of structurally novelnatural products. As part of an ongoing investigation of the bioactive chemical constituentsfrom marine organisms collected in the South China Sea, studies on four zoobenthosincluding three marine sponges (Agelas mauritiana, Pseudoceratina sp., Hyrtios sp.) andone marine bryozoan (Bugula neritina) led to the isolation and determination of64metabolites. Among these compounds, eight of them were new compounds. Theirantimicrobial, antimalarial, antileishmanial, cytotoxic, anti-HCV, cannabinoidreceptor-binding activities have been evaluated.23compounds (A1~A23) were isolated and purified from the Paracel Islands marinesponge Agelas mauritiana by solvent extraction,1H NMR guided-isolation, andchromatography methods including VLC, MPLC, HPLC on silica gel, ODS and SephadexLH-20. These compounds were identified by1H NMR,13C NMR,1H-1H COSY, HSQC,HMBC, NOESY, MS and circular dichroism as:(–)-ageloxime D (A1),(–)-8′-oxo-agelasine D (A2), ageloxime B (A3),(–)-agelasine D (A4),(+)-2-oxo-agelasidineC(A5), methyl (2Z,6S*,8R*,9E)-3,6-epoxy-4,6,8-triethyl-2,4,9-dodecatrienoate (A6),5α(H)-cholestan-3-one (A7),(3β)-stigmast-7-en-3-ol (A8),(+)-curcudiol (A9), dehydrocurcudiol (A10)4-bromo-N-(butoxymethyl)-1H-pyrrole-2-carboxamide (A11), N-(2-hydroxyethyl)-1H-py-rrole-2-carboxamide (A12),9-Methyl-9H-adenine (A13), aaptamine (A14), uracil (A15),thymine (A16), ethyl1H-Indole-3-carboxylate (A17),4,5-dibromopyrrole-2-carboxamide(A18),4,5-dibromopyrrole-2-methylformate (A19),1H-pyrrole-2-carboxylic acid (A20),n-tricosane (A21), hexadecane (A22), hexadecanoic acid (A23). The four compounds A2,A3, A5and A11were new compounds, Compounds A1and A3both showed antifungalactivity against Cryptococcus neoformans and antileishmanial activity against Leishmaniadonovani in vitro. Compound A3also exhibited antibacterial activity againstStaphylococcus aureus and methicillin-resistant S. aureus (MRS) in vitro.18compounds (B1~B18) were obtained from the Paracel Islands marine spongePseudoceratina sp by LC-MS guided-isolation and chromatography methods includingVLC, MPLC, HPLC on silica gel, ODS and Sephadex LH-20. Their structures wereidentified by spectroscopic analysis as fistularin3(B1), aerothionin (B2), homoaerothionin (B3), purealidin R (B4), hemifistularin3(B5),7-bromocavernicolenone (B6),cavernicoline1(B7), dienone B (B8), aeroplysinin-2(B9), subereaphenol B (B10),acetamide (B11),2,3-dibromo-5-(methoxymethyl)benzene-1,4-diol (B12),2-oxazolidinone(B13),2,5-cyclohexadiene-1-acetamide (B14),1H-Indole-3-carboxamide (B15), uracil(B16), aaptamine (B17),(3β)-stigmast-5-en-3-ol (B18). These metabolites included14brmo-derivatives, one of them (B12) was a new compound. Their antimicrobial,antimalarial, antileishmanial, cytotoxic, cannabinoid receptor-binding, neuro-protectionactivities have been evaluated. The antimicrobial assays of the brmo-metabolites indicatedthat compound B8exhibited antimicrobial activities against Staphylococcus aureus,methicillin-resistant S. aureus (MRS) and Escherichia coli in vitro. Compounds B4and B8showed antileishmanial activity against Leishmania donovani in vitro. In the cannabinoidreceptor-binding assay, B10exhibited selective affinity to CB1receptor: it has higheraffinity to the CB1receptor than the CB2receptors, and also has higher affinity to theKappa and Mu opioid receptors than the delta receptor. Compounds B1, B7and B8showed antimalarial activity against chloroquine sensitive (D6, Sierra Leone) and resistant(W2, Indo China) strains of Plasmodium falciparum. Compounds B4, B5, B6, B7, B8, B10and B12showed cytotoxicity against cancer cell line HepG2. The anti-HCV, anti-solidtumor, microglia protection bioassays of these brmo-compounds are currently ongoing. Inaddition, the biotransformaion work of aerothionin (B2) has being done, one newbrmo-metabolite was found.Seven metabolites (C1~C7) including five sesterterpenes were isolated from theParacel Islands marine sponge Hyrtios sp. by methods including VLC, MPLC, HPLC onsilica gel, ODS C-18and Sephadex LH-20. Their structures were identified byspectroscopic analysis as: sesterstamide (C1),12-epi-O-deacetyl-19-deoxy-scalarin (C2),16-O-Deacetyl-16-epi-scalarolbutenolide (C3), heteronemin (C4), scalarolide (C5), methyl(2Z,6S*,8R*,9E)-3,6-epoxy-4,6,8-triethyl-2,4,9-dodecatrienoate(C6),(3β)-stigmast-5-en-3-ol (C7). Compound C1was a new N-containing scalarane sesterterpene.Compound C2~C6showed cytotoxicity against cancer cell line HCT-116.16compounds (D1~D16) were isolated from marine bryozoan Bugula neritina bymethods including VLC, MPLC, HPLC on silica gel, ODS and Sephadex LH-20. Theirstructures were identified by spectroscopic analysis, they were: bryostatin8(D1),bryostatin19(D2), bryostatin4(D3), bryostatin6(D4), bryostatin10(D5), bryostatin18(D6), bryostatin5(D7),3β,24(S)-dihydroxycholesta-5,25-dien-7-one (D8), 3β,25-Dihydroxycholesta-5,23-dien-7-one (D9),24-methyl-cholesta-5,22(E)-dien-3β,7α-diol (D10), cholesta-5-ene-3β,7α-diol (D11), cholesta-5-ene-3β,7β-diol (D12),(3β,22E)-ergosta-5,22-dien-3-ol (D13),(3β,22E)-cholesta-5,22-dien-3-ol (D14),(3β)-cholest-5-en-3-ol (D15), n-hexadecoic acid (D16). These compounds included sevenbryostatins and eight steroids. Compounds D7and D8were new compounds, whichshowed cytotoxicity against cancer cell lines HepG2, HT-29, and NCI-H460.This dissertation describes the details of isolation and structure elucidation ofmetabolites from three marine sponges and one marine bryozoan collected from SouthChina Sea, the related bioactivities of the compounds were also reported. In conclusion,Ocean offers human an unparalleled source of novel and biologically active molecules, andthe studies of marine natural products can not only let us know what the amazing moleculestructure is, but also help us understand how the molecules can act on ourselves.
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