Secondary Metabolites From Two Strains Of Marine Nereid Gut Fungi And Its Bioactivities

Gut symbiotic fungi of marine animals can produce many bioactive secondary metabolites with novel structures which is an important part of marine microorganism and a significant source of new natural products.In order to find new secondary metabolites with novel structures and bioactivities,two strains of gut fungi SCD1-1 and SCHe3-3 living in a marine nereid were selected to investigate the secondary metabolites.Twenty-one compounds were isolated through Sephadex LH-20 column chromatography,silica gel column chromatography,silica gel thin layer chromatography and high performance liquid chromatography.Compounds 1-17 were isolated from the fungus Arthrinium sp.SCD1-1 and determined by spectral analysis of IR,MS,UV and NMR.These compounds included three polyhydroxyacid methyl esters,one aliphatic acid,four xanthone derivatives,one anthraquinone,two pyrone derivatives,two isocoumarins,two sesquiterpenes,one sesterterpene and one steroid.Compounds 1-5 are new ones.Compounds 18-21 were isolated from the fungus Microsphaeropsis sp.SCHe3-3,and one of them is new macrolide(18).Antibacterial activities of compounds 1-5,6,8,10,13,15,18 and 19 were tested by Kirby-Bauer Paper flakes diffusion method and the results showed that compound 10 showed some antibacterial activity against Staphylococcus,epidermidis and Staphylococcus.aureus with a concentration of 20 ug/small piece of paper,and other compounds do not show any activity.In addition,the cytotoxicity of compounds 1-5,6,8,10,13,15,18 and 19 was tested using SRB method.The result showed that all of these compounds had no obvious cytotoxic activity against PC3 cells.