Evaluation of in vitro antimicrobial properties of tannins isolated from the leaves of Vitex doniana Sweet. (Verbenaceae)

Abstract

Introduction: Vitex donniana Sweet is a medicinal plant used in traditional medicine in Nigeria for the treatment of many infections and ailments. The therapeutic effects have been attributed to high content of phenolic compounds such as tannins. Objective: To evaluate the antimicrobial effect of the tannins leaf extract against isolates of Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli Salmonela typhi and Candida albicans.Materials and Methods: The tannins content of the leaves was extracted by solvent extraction procedure and tannins confirmed using lead sub-acetate, bromine water and ferric chloride tests. Two-fold serial dilutions of 5mg/ml, 2.5mg/ml, 1.25mg/ml, 0.625mg/ml and 0.3125mg/ml were made. The antimicrobial assay was determined using the agar well diffusion method. The inhibitory effect was determined through diameter of inhibition zone. Results: The results showed that the minimum inhibitory effect against all the microbial isolates occurred at 2.5mg/ml concentration. The inhibitory effect was found to be dose dependent. The most sensitive microorganisms were Salmonella typhi and Candida albicans at concentration of 0.3125mg/ml and the most resistant microbial isolate was Staphilococcus aureus.Conclusion: The results showed that the tannins leaf extract of Vitex doniana has remarkable antimicrobial property. This confirms that the tannin constituent of the plant plays important role in its antimicrobial property.