African Journal of
Food Science

  • Abbreviation: Afr. J. Food Sci.
  • Language: English
  • ISSN: 1996-0794
  • DOI: 10.5897/AJFS
  • Start Year: 2007
  • Published Articles: 775

Full Length Research Paper

Two withanolides from Withania somnifera (solanaceae) and activity of methanolic extracts against fungal and bacterial pathogens that affects food crops

Regina Chepkorir
  • Regina Chepkorir
  • Department of Chemistry, Egerton University, Kenya.
  • Google Scholar
Josphat Clement Matasyoh
  • Josphat Clement Matasyoh
  • Department of Chemistry, Egerton University, Kenya.
  • Google Scholar
Isabel N. Wagara
  • Isabel N. Wagara
  • Department of Biological Sciences, Egerton University, Kenya.
  • Google Scholar


  •  Received: 16 August 2016
  •  Accepted: 15 September 2016
  •  Published: 31 May 2018

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.