Varvain Glucoside from the Stem Bark of Ceiba Pentandra Controls Postharvest Loss inDioscorea alata Tubers

Ceiba pentandra is a plant renowned for its wound healing ability and antimicrobial characteristics. This work focused on isolating and characterizing antimicrobial compounds from the stem bark of Ceiba pentandra. Plant extracts were prepared by successive maceration of the ground stem bark in hexane, ethyl acetate, and methanol. The extracts were subjected to column chromatography on silica gel to isolate compounds that could be used as antimicrobial agents against tuber rot in Dioscorea alata. The compounds obtained were varvain-3-O-glucoside, ferulic acid, catechin-3-O-glucoside, and a mixture of sitosterol and stigmasterol. The compounds were identified using NMR and high-resolution mass spectrometry techniques, and their identities were verified by comparing their data with information found in literature reports. Antimicrobial assays of the extracts and isolated compounds against bacterial and fungal isolates from Dioscorea alata tubers revealed that the compounds are active against tuber rot bacteria and fungi with MICs between 50.0 and 12.5 µg/mL. The extracts were less active, with MICs between 50.0 and 25.0 µg/mL. In conclusion, the relatively low MICs indicate the ability of these compounds to inhibit the growth of pathogenic microorganisms commonly associated with postharvest losses of Dioscorea alata tubers.