Study On Chemical Constituents And Bioactivities Of A Marine Sponge And Two Gorgonian Corals From South China Sea

Marine natural products with complex chemical structures and diversitybiological activities have attracted a great deal of attention from scientists in the fieldsof pharmacology. In the past50years, drug research focused on marine organisms,and much of coral reef invertebrates. In our studies of searching for natural productswith unique structural features and diversity biological activities from marineorganisms, three coral reef invertebrates, the marine sponge Plakortis simplex,gorgonian coral Euplexaura curvata and Euplexaura robusta were been collected inthe China South Sea. The study includes isolation and structural elucidation of thechemical constituents, exploring the biosynthetic pathways of the novel compoundsand preliminary evaluation for bioactivities of pure compounds.By using silica column, Sephadex LH-20, ODS column, HPLC and etc,35compounds were isolation from the sponge Plakortis simplex and30compounds(1~30) were determined;15compounds were isolation from the gorgonianEuplexaura curvata and11compounds (31~41) were determined;25compoundswere isolation from the gorgonian Euplexaura robusta and22compounds (31~52)were determined. By means of physico-chemical properties and spectral analysis(NMR，MS，IR，UV，CD，Mosher’s method), structures of52pure compounds wererespectively determined. Among them there are11polyketides (1~7,9~12),28alkaloids (8,13~15,22~29,31~37,42~43,46~52),9sterols(19~21,38~41,44~45),3diketopiperazines (16~18),1benzene derivative. The antitumor activities againstseveral caner cell lines of pure compounds were assayed by MTT and SRB methods.Among them4compounds (3、5~6、42) with significant bioactivities were found. Theinhibitory activity against the c-Met kinase of pure compounds was assayed usingELISA method. Among them2compounds (4,8) with significant bioactivities were found.In this paper,11metabolites including7polyketides (1~7),4alkaloids (8,31,42~43), were found for the first time. Next, polyketides, characteristic secondarymetabolites from the sponge Plakortis simplex on which a great deal of continuingresearch had focused, were found once again with a large number, especially thediscovery of the compounds (1~2) with unique structural characteristic ofepoxide-linked α,β-unsaturated-γ-lactone ring and the compound (3) featured an rarepolyketide skeleton with a cyclopentane for the first time, greatly enhanced thesponge habitat specificity. The absolute configurations of polyketides (1~4) aredetermined by analyzing the NOESY and CD spectra, whereas polyketides (5~6) byanalyzing the NOESY and Mosher’s method. Third, The reports of alkaloidsdiscovered from gorgonians are a few, whereas the isolation of tetraprenylatedalkaloids from the gorgonians Euplexaura curvata and Euplexaura robusta,respectively, increased the numbers of alkaloids discovered from gorgonians, but alsowas a power proof that the gorgonians of the same genus may have a close geneticrelationship as well as significant species-specific differences in chemical constituents.At last, The bioactive marine secondary metabolites of invertebrates from coral reefecosystem provided diversity of compounds for the discovery of lead compounds andexploration of new medicinal bio-resources.