A new derivative of epicatechin glucopyranoside, (2R,3R)-3,7,4'-trihydroxy-5,3'-dimethoxyflavan 7-O-β-d-glucopyranoside (1), together with three mononuclear phenolic acid esters, methyl orsellinate (2), ethyl orsellinate (3) and methyl β-orcinolcarboxylate (4) were isolated from the bark of Styrax suberifolius. The structures of 1-4 were determined on the basis of extensive analysis of NMR and MS spectra combined with chemical hydrolysis. The antifungal activities of the isolated compounds against three plant pathogenic fungi, Alternaria solani, Fusarium oxysporum and Phomopsis cytospore were evaluated using radial growth inhibition assay. Compounds 2, 3 and 4 exerted selective inhibitory activities against the tested fungi. Among of them, methyl β-orcinolcarboxylate (4) exhibited obvious inhibitory effect against P. cytospore, with an inhibition rate of 86.72% at 100 μg/ml.
Keywords: Styrax suberifolius; antifungal activity; epicatechin derivative; flavonoid glycoside.