Phytochemical investigation of leaves extracts of Dodonaea angustifolia and evaluation of its antibacterial activities

Abstract

Natural products from plants and other natural sources have been providing noble and clinically active drugs. The plant-based traditional medicinal system continues to play significant role in health care, in which approximately 80% of the world’s population still rely mainly on traditional medicines for their primary health-care. Therefore, this study was undertaken to identify bioactive secondary metabolites from the leaves of Dodonaea angustifolia for antibacterial activiities. With this regard, the air dried leaves of Dodonaea angustifolia was extracted exhostvely with chloroform/methanol (1:1) by maceration. The chloroform/methanol extract was then partioned between ethyl acetate and H 2 O to give ethyl acetate extract. Both CHCl3 /CH3 OH and ethyl acetate crude extracts were evaluated for their antibacterial activity against four bacterial strains, namely; Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853) and Enterococcus faecalis (ATCC 29212). The ethyl acetate portion crude extracts showed antibacterial activities with zone of inhibition ranging from 7-22 mm. The observed activity against S. aureus (zone of inhibition, 22 mm) for ethyl acetate soluble extract was comparable with that of the referance drug, gentamycin, which desplayed 23 mm zone of inhibition on the same strain. Based on the superior activity of the ethyl acetate extract, it was subjected to fractionation using column chromatography (CC) over silica gel eluted with petroleum ether containing increasing amounts of ethyl acetate, which resulted with the identification of 5,7-dihydroxy-3,4‘6-trimethoxyflavone (1A) which showed moderate antibacterial actvity against the tested strains (E.faecali, E.coli, S.aureus, and P. aeruginosa). The structure of the isolated compound was established using 1D ( 1 H, 13 C) and 2D NMR spectroscopic techniques. Devising alternative method of extraction as well as carrying the antioxidant, antifungal and antiplasmodium activities of this plant are recommended for further researchers