Bioactive compounds from the endophytic fungus Colletotrichum sp. CRI535-02 isolated from Piper ornatumKamolchanok Tianpanich
( M.Sc. )
Chemical investigation of a crude broth extract of the endophytic fungus Colletotrichum sp. CRI535-02, which was obtained from the stems of Piper ornatum, gave five known isocoumarins including monocerin (1) and its derivative 7-O-desmethylmonocerin (2); fusarentin ether derivatives, fusarentin 6,7-dimethyl ether (3), fusarentin 6-methyl ether (4), and compound (5); and a new phthalide (6). The cytotoxic activity toward HepG2 cell line of monocerin derivative 2 was in the same order of magnitude as that of a standard anticancer drug, etoposide. Compound 4 was active toward HepG2 cell line. Compounds 2 and 4 could scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals (respective IC50 values of 23.4 and 16.4 μM) and inhibit superoxide anion radical formation (respective IC50 values of 52.6 and 4.3 μM). The C-7 hydroxyl group in 2 and 4 was found to be important for such radical scavenging activities. Isocoumarins 13 and a phthalide 6 showed potent antioxidant activity in the ORAC assay. Structures elucidation of the isolated compounds was performed by analysis of spectroscopic data (NMR, UV, IR and MS).