Secondary Metabolites And Their Chemotaxonomic Significance Of The Gorgonians Subergorgia Suberosa And Menella Kanisa From The South China Sea

Marine ecological environment makes the fierce competition among marinespecies. Soft gorgonian belonging to inferior invertebrates, which produce secondarymetabolites with the nature of the chemical defense in a fierce marine ecologicalenvironment in order to survive and reproduce. In recent years, a lot of novel structureof secondary metabolites were found in the case of coral. Some secondary metabolitesmight be characteristic constituents of the gorgonian, and may be useful aschemotaxonomic markers for the gorgonian.In this paper, the bioactive secondary metabolites from Subergorgia suberosawhich were respectively collected from Meishan and Xisha seas, and Menella kanisaof the South China, were investigated according to the modern technology of marinenatural products. Column chromatography on silica gel and Sephadex LH-20, andsemi-preparative HPLC were used to isolate and purify the secondary metabolites.The structures of isolated compounds were finally identified by spectroscopic analysisincluding NMR, MS, IR and UV.55compounds were separated, and the structures of42compounds were elucidated, to carry out the research of biological activities of thesecondary metabolites.In this study,12compounds were separated from gorgonian Subergorgiasuberosa from Meishan seas of the South China Sea. There are: four pregnanesteroids (1–4), four other steroids (5–8), one suberosane sesquiterpene (9), twoglycerol ether (10,11), one lipid (12).23compounds were separated from gorgonianSubergorgia suberosa from Xisha seas of the South China Sea. There are: eightpregnane steroids (1–4,13–16), six other steroids (17–22), five suberosanesesquiterpenes (9,23–26), two alkaloids (27,28), one ceramide (29), one alcohol (30). Specially, compounds1,14and15are new natural products. Five same compoundshave been isolated from different seas with the same species of coral (Compounds1–4and9are repeated compounds). Comparatively studying S. suberosa collectedfrom different time and seas, and discovered that pregnane steroids with17-acetylgroup are characteristic constituents of of Subergorgia suberosa. Firstly studyingchemotaxonomic significance of chemical constituents of Subergorgia suberosa.Compared with other species in the genus Subergorgia, pregnane steroids with17-acetyl group were only achieved from S. suberosa, suggesting that the17-acetylpregnane steroids might be characteristic constituents of S. suberosa, and may beuseful as chemotaxonomic markers for the species S. suberosa.12compounds were separated from gorgonian Menella kanisa from Weizhoudaoseas of the South China Sea. There are: nine guaiane sesquiterpenoids (31–39). Onesuberosane sesquiterpene (40); Two steroids (41,42). Further highly oxygenatedguaiane lactones containing a,-unsaturated--lactone moiety might becharacteristic constituents of S. suberosa, and may also be useful as chemotaxonomicmarkers for the species Menella kanisa.The bioactive compounds from S. suberosa and Menella kanisa were evaluatedby four models: lethal to brine shrimp (Artimia salina), antibacterial, ichthyotoxic andcytotoxic activity models. Compounds1–4,13–16,31–33and35–37showedinhibition against brine shrimp at the concentration of50μg/mL. Compounds9,23,24and26exhibited potent antibacterial activity against Staphylococcus albus with theMIC value of5.0μg/mL,5.8μg/mL,5.3μg/mL and5.2μg/mL; Compound23exhibited potent antibacterial activity against Pichia guilliermondii with a MIC valueof5.8μg/mL, and compound16against Bacillus cereus with a MIC value of6.3μg/mL; Compounds34and38exhibited potent fish toxicity toward zebrafish embryo.34displayed tail teratogenicity of zebrafish with the EC50value of2.12μg/mL(72h),and death of zebrafish with the LC50value of2.02μg/mL(72h);38showed death ofzebrafish with the LC50value of1.56μg/mL (72h); Compound3showed potenttoxicity toward HeLa with the IC50value of25.40μg/mL. Come to preliminaryconclusion: pregnane steroids and suberosane sesquiterpenes are main bioactive secondary metabolites in gorgonian S. suberosa.It is meaningful for the discovery of new active lead compounds from marinebiological resources to deeply launch the research of chemical defense substances andespecially continue to discover chemical defense compounds. Furthermore, theresearch of characteristic constituents suggested chemotaxonomic significance of thegorgonians S. suberosa and Menella kanisa.