In-vitro assessment of antibacterial activity of crude methanolic and aqueous extracts of Mitracarpus villosus

Globally, there is an increasing report of bacterial resistance to currently available antibiotics. The urgent need for newer therapeutic modalities was the incentive for the current evaluation of bactericidal and inhibitory effects of methanolic and aqueous extracts of Mitracarpus villosus on selected antibiotic resistant Gram-positive and Gram-negative bacteria. Ten-fold serial dilution was used to test the effects of the extracts. The percentage yield of extractable components was 22% for methanol and 8.3% for water. The minimum inhibitory concentration (MIC) of methanolic extract was 0.001 mg/mL against Streptococcus pyogenes, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, and Salmonella Typhi showing resistance to antibiotics and 0.01 mg/mL for Staphylococcus aureus, Bacillus subtilis, and Klebsiella pneumoniae while the minimum bactericidal concentration (MBC) was 0.1 mg/mL for all the isolates except S. aureus and E. coli with MBC of 0.01 mg/mL. Similarly, the MIC of aqueous extract was 0.01 mg/mL for S. pyogenes, S. aureus, B. subtilis, and K. pneumoniae; 0.1 mg/mL against S. faecalis and E. coli; 0.001 mg/mL against P. aeruginosa and S. typhi. The MBC of the aqueous extract at 0.1 mg/mL was active against S. pyogenes, S. faecalis, P. aeruginosa, K. pneumonia, and S. typhi; 1.0 mg/mL was active against S. aureus, B. subtilis, and E. coli. Findings from the present study indicate that the extracts of M.  villosus have the potential to be used for treatment and cure of infections caused by selected bacteria. The methanolic extracts show more potent activity. Further study on a larger scale at varied concentrations including a test for potential toxicity in cultured cells are needed to depict their safety profiles before recommendation for inclusion in the antibacterial armamentarium.   Key words: Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), M. villosus, bioactive compounds.