Antibacterial Efficacy of Vernonia Amygdalina (Bitter Leaf) on Some Bacteria Isolated from Locally Produced Soymilk Sold in Different Markets in Enugu Metropolis

Abstract

This study aimed to investigate the antibacterial efficacy of Vernonia amygdalina (bitter leaf) on some bacteria isolated from locally produced soymilk in different markets in Enugu metropolis. The test organisms were identified using standard microbiological methods. The antibacterial activities of ethanolic and methanolic extracts of Vernonia amygdalina (bitter leaf) were carried out by agar well diffusion method. Ethanolic and methanolic extracts of the plant were used at varying concentrations of 200, 100, 50, 25, 12.5, 6.25, 3.125, 1.56, and 0.76 mg/ml, respectively. The two extracts were found to show antibacterial activity. However, the ethanolic extract had more activity than the methanolic extract. The inhibition zone diameter (IZD) of the ethanolic extract varied from 4 – 20 mm, while that of the methanolic extract varied from 4 -16 mm for all the bacteria tested. The minimum inhibitory concentration (MIC) of ethanolic and methanolic extracts varied with bacteria; 1.56 mg/ml respectively for Staphylococcus aureus, 3.125 mg/ml and 6.25 mg/ml for Escherichia coli, 6.25 mg/ml and 25 mg/ml for Salmonella spp, 3.125 mg/ml and 6.25 mg/ml for Klebsiella spp, and 3.125 mg/l for the typed strains (E. coli NCTC 12241, K. pneumoniae NCTC 13368). The ciprofloxacin (50mg/ml) used as a standard antibiotic compared well with the plant extracts at 200 mg/l. The phytochemical analyses revealed the presence of alkaloids, saponins, flavonoids, glycosides, and tannins. This study shows that plant extract can be used as an alternative to conventional antibiotics.