The Secondery Metabolites And Their Bioactivies Of A Gorgonian Coral And Two Sponge-Derived Fungi

Marine bioresources are an important source for drug discovery. Tropical coralreef ecosystem with rich biodiversity and chemical diversity has become a hotresource for the research on marine natural products and drugs. Especially, marineinvertebrates, lacking the capability of physical defense, and their symbioticmicroorganisms depend on the chemical defensive substances, which makes animportant resources for the discovery of drug lead compounds. More attentions havebeen payed to the marine chemical defensive substances with various pharmacologicalactivities in the fields of natural product chemistry and pharmacology.In present study, the secondary metabolites from a gorgonian and two fungi fromthe South China Sea were isolated and identified under the guidance of bioassay. Thebiological activities of the isolated compounds were evaluated.Investigation on the gorgonian Carijoa sp. led to the isolation of six steroids(1–6), including four pregnant steroids (1–4) and two ergosterols (5,6). Theirstructures were elucidated by NMR spectroscopy and compared with the previous datareported in the literature. Among the six compounds, compound1was identified as anew pregnant steroid. Compounds1,3and4showed cytotoxicity against Bel-7402with the IC50value of9.33,11.02and18.68μM, respectively. Additionally,compounds1–4showed weak cytotoxicity against MRC-5, indicating potential clinicalvalue. Compound1exhibited promising inhibitory activity against Pseudomonas putida,with an MIC value of31nM, which was approximately5-fold higher thanciprofloxacin (MIC=156nM). Compounds2and3showed inhibitory activity againstBacillus cereus and Tetragenococcus halophilus. Compounds1and4did not expressany significant antimicrobial activity, suggest that acetyl group might play animportant role in enhancing the antibacterial activity of these two compounds.13compounds were isolated from the Aspergillus insulicola (MD10-2) of theSouth China Sea sponge, including five sesquiterpenes (7–11) and eight ergosterols(5,12–18). While compound7was identified as a new compound and its absolute configuration was determined by Mosher reaction. Particularly, compound7–11wereisolated from this fungal species for the first time.It was worth noting that natural products with nitro group were very rare. Thefive sesquiterpene lactones isolated from Aspergillus insulicola (MD10-2) allcontained nitrobenzene. The cytotoxic activity of the five sesquiterpene lactones wereevaluated against five cell lines, viz, Bel-7402, A-549, Hela, H-460and HO8910.Among them, Compound8showed significant activity against H460, with an IC50of6.9μM, which was closely similar to the positive control taxol and it also exhibitedmoderate cytotoxicity against other cell lines. After structural modification of8, itscytotoxicity was significantly reduced, indicating that the hydroxy was an importantactive group of8.Three known compounds (20–22) were isolated from from the fermentation brothof sponge-derived fungus Aspergillus terreus PF26. Among them, compound21wasa precursor of terrein, which verified the biosynthetic pathway of terrein.In this study, the secondary metabolites from a gorgonian and twosponge-derived fungi were isolated and their structures were identified, and theirbiological activities were also evaluated. The results should supply with the valuableinformation for further reaearch on the relationships between structure and activityand also provide an important research idea for the discovery of marine leadcompounds from the marine microorganism.