Antifungal properties of a new terpernoid saponin and other compounds from the stem bark of Polyscias fulva Hiern (Araliaceae)

In our previous studies, it was evident that the dichloromethane-methanol (1:1 v/v) stem barks extract of Polyscias fulva and fractions (ethyl acetate, n-butanol and residue) demonstrated interesting antidermatophytic activities. So, as a continuity of that, this work aimed at identifying active principles with antifungal properties from P. fulva that could be used as markers for possible standardization of this plant as phytomedicine. The ethyl acetate, n-butanol and residual fractions of the dichloromethane-methanol (1:1 v/v) stem bark extract of Polyscias fulva were further fractionated by column chromatography and the structures of isolated compounds elucidated based on their spectroscopic data in comparison with existing literature information. Antifungal activity was assayed by broth microdilution techniques on yeasts and dermatophytes spores. The fractionation of the crude dichloromethane-methanol (1:1 v/v) stem bark extract of Polyscias fulva led to the isolation of 10 known compounds (1 to 10) and one new saponin (11: 3-O-[α-L-rhamnopyranosyl (1-2)-α-L-arabinopyranosyl]-28-O-[α-L-4-O-acetyl-rhamnopyranosyl (1-4)-β-D-glucopyranosyl-(1-6)-β-D-glucopyranosyl]-hederagenin). Among these compounds, 3-O-α-L- arabinopyranosyl-hederagenin and 3-O-[α-L-rhamnopyranosyl (1-2)-α-L-arabinopyranosyl]-hederagenin were the most active on the tested fungi with MIC values ranging from 0.78 to 100 μg/ml against both yeasts and dermatophytes. The results of this work constitute a step forward in the possible development of an antidermatophytic phytomedicine from Polyscias fulva stem bark, the isolated compounds being possible markers for the standardisation.