Antimicrobial screening and chemical investigation of the root wood ethanolic extract of Dalbergia saxatilis (Fabaceae)

Abstract

The ethno-medicinal uses of Dalbergia saxatilis have made it a useful plant for both chemical and biological investigations. The dried root wood was extracted with 95 % ethanol to obtain a crude extract, part of which was partitioned into acidic, basic, polar and non-polar neutral fractions. The crude extract was subjected to preliminary phytochemical screening and both the crude extract and fractions were screened for antimicrobial activity. The qualitative phytochemical investigation showed the presence of cardenolides, tannins, alkaloids, saponins, steroids, terpenoids, and resins. The antimicrobial activity of the crude and the different fractions was determined against some bacteria, including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa and fungi, including Candida albicans, and Aspergillis niger, using different culture media for sensitivity test, Minimum Inhibitory Concentration and Minimum Bacteriocidal Concentration determinations. The crude extract and fractions exhibited strong concentration-dependent activity against the test organisms at various concentrations. Column chromatographic fractionation of the antimicrobial neutral polar fraction, followed by GC-MS analysis of column fractions revealed the presence of metabolites, including oleic acid, oleamide, 4-phenylbut-3-ene-1-yne and homopterocarpin, known to have bioactivities that are of medicinal significance. Their presence therefore supports the ethno-medicinal uses of the plant in some Nigerian communities.