PHYTOCHEMICAL SCREENING, ANTIMICROBIAL ASSESSMENT, AND ISOLATION OF A NOVEL BIOACTIVE FRIEDELANE-TYPE TRITERPENOID FROM THE STEMBARK EXTRACTS OF Uapaca ambanjensis Leandri.

Abstract

The hexane, dichloromethane, ethyl acetate and methanol extracts of the stem bark of Uapaca ambanjensis were investigated for their phytochemical constituents and activity against selected microorganisms. Whereas all the phytochemicals, except anthraquinones, are indicated in various extracts, the most impressive antimicrobial potencies of extracts compared to standard drugs were observed for methanol (against Salmonella typhi and Candida albicans), n-hexane (against Staphylococcus aureus, C. albicans, S. typhi and Klebisiela pneumoniae) and ethyl acetate (against Pseudomonas aeruginosa). Chromatographic separation and purification of the methanol extract led to the isolation of compound 1 (labelled G24) which upon characterization using 1D and 2D NMR was elucidated to be a novel friedelane–type pentacyclic triterpenoid, 2β-propanoyloxy-friedelan-3-one. In vitro antimicrobial screening of the new compound showed that it has both gram-positive and gram-negative antibacterial, and antifungal potencies with the strongest activities against P. aeruginosa, C. albicans, S. aureus and Streptococcus pyogenes. It is most likely a medicinal principle or antibiotic with activity against ailments for which the stated microbes are implicated, and may also account for the ethnomedicinal uses of the crude plant extract to treat typhoid fever, other fevers, skin diseases and stroke.