Antimicrobial Activity and Phytochemical Screening of Methanolic Leaf Extract of Vernonia amygdalina

Aims: Crude methanolic leaf extract of Vernonia amygdalina was evaluated to determine its bioactive constituents, the antimicrobial properties, measure the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against some selected bacterial organisms. 
Place and Duration of Study: The investigation was carried out at University of Maiduguri in Borno State, Nigeria. The herb obtained from Lake Chad Research Institute were identified and validated by the department of Forestry and wild life, Mohammet Lawan College of Agriculture (MOLCA) in Maiduguri, Borno State. 
Methodology: Crude methanolic leaf extraction of the plant, qualitative phytochemical screening, antimicrobial sensitivity against some disease-causing organisms, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were carried out. 
Results: Phytochemical screening of V. amygdalina leaves extract revealed the presence of tannins, saponins, terpenoids, flavonoid, carbohydrates and cardiac glycosides. The antimicrobial sensitivity shows P. aeruginosa, had the highest sensitivity with effect at all concentrations (26 mm at 1000 mg/ml), the lowest against Salmonella typhi were 9 mm at 1000 mg/ml and 7 mm at 200 mg/ml, while the highest were 17 mm at 400 mg/ml and 14 mm at 200 mg/ml. When tested at all concentrations (200-1000 mg/ml), S. aureus, S. pyogenes, B. subtilis, Corynebacteria species, and K. pneumonia showed greater sensitivity than Salmonella typhi but less sensitivity to P. aeruginosa. Based on the outcomes of the MIC and MBC results, S. aureus was found to be sensitive to the extract at 100 and 200 mg/ml, while P. aeruginosa was found to have the highest sensitivity to the extract at all concentrations (25-200 mg/ml) with the exception of 12.5 mg/ml of the extract. 
Conclusion: The study highlighted the antimicrobial effects of V. amygdalina leave extracts on some pathogens thereby verifying the traditional healer’s claim.  Also, it was concluded that the extract of V. amygdalina contained pharmacologically active phytochemicals which could be responsible for the numerous medicinal properties exhibited by the plant leaf extract.