Antimicrobial activities of Vernonia tenoreana

Abstract

The antimicrobial activity of Vernonia tenoreana was investigated. Crude extracts and solvent fractions of the leaf and bark of V. tenoreana were obtained using methanol and distilled water (2:3, v:v),
ethylacetate, chloroform, and n-hexane as solvents of extraction. The crude and solvent fractions showed broad spectrum activities against Staphylococcus aureus, Streptococcus faecalis, Bacillus
subtilis, B. cereus, Shigella dysenteriae, Klebsiella pneumonia, Pseudomonas aeruginosa and Proteus vulgaris, with zones of inhibition ranging from 1.7 to 18.3 mm. The leaf extracts showed better
antimicrobial activities, as the minimum inhibitory concentration (MIC) values for most of the isolates was 10 mg/ml with a least value of 5 mg/ml recorded for P. aeruginosa (NCIB 950). On the contrary, in
the case of bark extract, 15 mg/ml was the MIC value recorded for most of the test isolates with the least value of 10 mg/ml recorded for S. aureus, B. subtilis, and K. pneumoniae. Out of all the solvent
fractions, the chloroform fractions exhibited the highest antimicrobial activities. The bark extracts exercised antifungal activities against Candida albicans, Aspergillus niger and A. flavus, while the leaf
extract was inactive against all the fungal isolates. Phytochemical constituents revealed the presence of saponins, tannins, and anthraquinones in the bark extracts, while, tannins, anthraquinones, and
cardenolides were present in the leaf extract.