Abstract

Methanolic extract obtained from the dried leaves of Withania Somnifera was subjected to column chromatography leading to the isolation of two withanolides. Their structures were elucidated using 1D and 2D NMR spectroscopy. The isolated withanolides were determined to be 5α, 17β-dihydroxy-6α, 7β-epoxy-1-oxo-witha-2, 24-dienolide (1) and 4, 5, 6, 15-tetrahydroxy-1-oxo-witha-7-enolide (2). The bioassay of the methanolic extracts showed activity against the fungal pathogens, Fusarium moniliforme, Fusarium graminearum, Colletotrichum lindemuthianum and Pythium spp. The extract was also active against bacterial pathogens, Xanthomonas campestris pv. phaseoli and Pseudomonas syringae pv. phaseolicola. The withanolides did not show any bioactivity indicating that they are either active only synergistically with other compounds within the extracts or there are other active compounds in the extract.

Key words: Withania somnifera, withanolides, methanolic extract, antifungal, antibacterial.