Leaf Extracts of Vernonia amygdalina Del. from Northern Ghana Contain Bioactive Agents that Inhibit the Growth of Some Beta-lactamase Producing Bacteria in vitro

Abstract

Aims: The current study was aimed at evaluating the phytochemical profile and in vitro bacteria growth inhibitory potential of different solvent leaf extracts of V. amygdalina from northern Ghana. Study Design: Different solvent extracts of the plant were quantitatively and qualitatively evaluated for phytochemicals. In vitro bacteria sensitivity assay of the extracts was evaluated using some beta-lactamase producing bacteria as test microbes. Methodology: Ethanolic, methanolic, petroleum ether and aqueous leaf extracts of Vernonia amygdalina were studied in vitro for growth inhibition against beta-lactamase producing bacteria such as Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa using agar well diffusion method. Saponins, flavonoids, glycosides, alkaloids, tannins, phenolics, reducing sugars, anthracenosides, terpenes and phytosteroids were determined qualitatively and quantified. Results: All the phytochemicals tested were found to be present in both the methanolic and ethanolic leaf extracts. The aqueous extract showed the presence of saponins, reducing sugars and anthracenosides. Glycosides, flavonoids, saponins and alkaloids were the only groups of phytochemicals found in the petroleum ether extract. The methanolic extract showed the greatest amount of saponins (14.23%), flavonoids (2.15%), alkaloids (7.49%), tannins (5.4%), terpenes (10.20%) and phenolics (8.24%). The methanolic extract at concentration of 4 mg/ml showed growth inhibitory activities against all the test organisms with zone of inhibitions ranging from 16.00+0.50 (against E. coli) to 20.50+0.03 mm (against S. aureus). The ethanolic extract showed activity against only two of the test organisms viz. 23.00+0.33 mm against P. aeruginosa and 12.00+0.00 mm against S. aureus at similar concentration. All test organisms were resistant to both aqueous and pet ether extracts. Conclusion: The antibacterial activities of the methanolic and ethanolic extracts were significant (P < 0.05) and may be mediated by the presence of saponins, flavonoids, tannins, terpenes and alkaloids. Results from present study corroborate previous findings and also presents methanolic leaf extract of the plant as a credible candidate for the discovery of new phytotherapeutic agents against the beta-lactamase producing bacteria tested.