Isocoumarins and dihydroisocoumarins from the endophytic fungus biscogniauxia capnodes isolated from the fruits of averrhoa carambola

Abstract

An endophytic fungus Biscogniauxia capnodes was isolated from a popular edible fruit Averrhoa carambola. The fungus was fermented in potato dextrose broth for 3 weeks, and then the culture broth and mycelium were extracted with ethyl acetate. Chromatographic separation of this extract furnished 2 isocoumarins, reticulol (1) and 6-O-methyl-reticulol (2), and 2 dihydroisocoumarins, 5-methylmellein (3) and 7-hydroxy-5-methylmellein (4). Compound 1 showed moderate antioxidant activity against 2,2′-diphenyl-1-picrylhydrazyl radicals (IC50 value, 58 μg/mL). This is the first report of the isolation of B. capnodes as an endophyte, as well as the compounds 1 to 4 from B. capnodes.