Evaluation of in-vitro antibacterial activity of extracts of Calpurina aurea, Vernonia amygdalina and Rumex nepalensis in Goba district, southeastern Ethiopia

Abstract

ABSTRACT The great majority of the rural populations in developing countries relies on traditional medicinal plants for treating different diseases. This study investigated the antibacterial activity of Calpurnia aurea, Vernonia amygdalina, and Rumex nepalensis collected from Goba District, Bale Zone, southeastern Ethiopia against five human bacterial test pathogens (Escherichia coli, Salmonella typhi, Staphylococcus aureus, Shigella dysenteriae and Pseudomonas aeruginosa). Plant specimens were extracted with 70% ethanol, 80% methanol, petroleum ether, and distilled water. The crude extracts were evaluated against test pathogens using agar well diffusion and micro dilution methods. The highest yield was achieved by aqueous extract of C. aurea leaf (16.6 mg/ml). The antibacterial activity of the plants’ extracts ranged from a zone of inhibition of 5.4 ± 0.4 mm to 23.0 ± 0.3 mm. Overall, the highest zone of inhibition (23 ± 0.3 mm) and the highest activity index (AI) comparable to 80% of inhibition by standard antibiotic ciprofloxacin (5 µg/disc) were revealed by the methanol extract of C. aurea leaves against S. aureus. The smallest minimum inhibitory concentration (0.78 mg/ml) was achieved by 80% methanol extracts of C. aurea roots and V. amygdalina leaves against S. aureus and E. coli, respectively. Our study revealed promising antibacterial activity of the evaluated plants.. Further studies are required to evaluate the active ingredients at the in-vitro and in-vivo levels.