| Seaweed is primary production of marine ecosystem food chain and the energy sources supplier of marine life. So there must be some allelopathic substances for struggling for the living space, safeguarding the increasing of the species. So separating and identification the metabolic products is one of the hot points of marine chemistry ecology. In addition, the marine inferior invertebrates in the coral reefs ecosystem contain lots of secondary metabolites with novel structure and obvious allelopathic activities, and have become a hot point biology resource for marine drugs lead compounds and marine drugs researching. Actually, they have become hot point biosourses for searching for the marine drugs lead compounds and marine drugs researching.In this paper, the allelopathic substances from Sargassum thunbergii and Sinularia sp.were investigated according to the methodology of chemical ecology combining with modern technology of marine natural products. The bioactive secondary metabolites were isolated and elucidated from the two species by column chromatography, Sephadex LH-20, HPLC and NMR, MS, IR, UV.32 compounds were separated. The structures of 26 compounds were elucidated.In this paper,12 compounds were separated from S. thunbergii. They were: 2-[(3S,7S,11S)-3-hydroxy-3,7,11,15-tetramethylhexadecyl]-3,5,6-trimethylcyclohex a-2,5-diene-1,4-dione (1),22-dehydrocholesterol (2), stigmast-5-en-3-ol (3), fucosterol (4), saringosterol (5), fucosterone (6), ergosterol peroxide (7), 1-(hexadecyloxy)-propane-2,3-diol(8),1-(15-methylheptadecyloxy)-propane-2,3-dio 1 (9),3,7,11,15-tetramethyl-hexadecane-1-ol (10), phytol (11),3-[(1-oxohexadecyl) oxy]-2-[[(9Z,12Z)-1-oxo-9,12-octadecadien-1-yl]oxy]propyl (12).14 compounds were separated from Sinularia sp.. They were:sinularolide N (13), lobomichaolide (14),14-acetoxy-3,4-epoxycembra-7,11,15-triene-17,2-olide (15), michaolide F (16), sinularolide C (17), presinularolide B (18),20-acetylsinularolide B (19), ergost-22-en-3-ol (20), ergost-5-en-3-ol (21), lumisterol (22), chimyl alcohol (23), 9,12-octadecadien-1-ol (24), octadecan-1-ol (25), hexadecan-1-ol (26). It was the first time to isolate and elucidate the secondary metabolites compounds 1,3～10 and 12 from S. thunbergii and compounds 13,15,16,18 and 24 from the soft coral Sinularia sp., of which, compound 13 was a new compound.The biological activities of the compounds from the two species were evaluated by two models:lethal to brine shrimp (Artimia salina) and zebrafish embryotoxicity model. Compounds 1,6 and 7 showed stronger inhibition against brine shrimp, the lethality rate were 70.8%,70.5% and 66.6% at the concentration of 50μg/mL. The case in Sinularia sp., compounds 16 and 19 showed stronger inhibition against brine shrimp, the lethality rate were 90.5%,90.0% under the concentration of 50μg/mL. Compound 19 showed higher rate of malformed egg, EC50μg/mL was 39.12. So compound 19 was deduced as one of the allelopathic substances in Sinularia sp. And the cembrane-type terpenoids were deduced as the allelopathic substances in Sinularia sp..In this paper, the allelopathic substances from S. thunbergii; Sinularia sp. were also evaluated. This study provided a basis for the research on the chemical defense substances of the algeas and soft corals. The marine chemistry ecology research thread and method were used to screening and discovering of the marine active natural compounds, for which, a novel research thread and method were proposed. |
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