In Vitro Antimicrobial Studies of Plait Aqueous Extracts of Some Nigerian Medicinal Plants

Medicinal plants have been used by man to treat various kinds of infections without scientfic pror of their efficacy. The Antimicrobial activities of aqueous extracts of four Nigerian medicinal plants namely: Solanum americanum, Euphorbia hirta, Cassia occidentalis and Telfaria occidentalis  were investigated against a wide range of isolated strains of bacteria by the disc diffusion method. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the extracts were also determined on the susceptible organisms. These plant extracts are used in Nigeria folklore medicine to treat infections of microbial origin. Aqueous extracts of the investigated plants showed antibacterial activities against different pathogenic bacteria. Among the pathogenic organisms  used, Staphylococcus  aureus, Pseudomonas aeruginosa, Klebsiella  pneumoniae  and Escherichia coli were susceptible to three of the aqueous extracts used at concentrations of 100μg/ml. The plant  extracts demonstrated broadspectrum antibacterial activity against the microorganisms tested. The Minimum Inhibitory Concentration (MIC) of Solanum americanum  was between 6.3μg/ml to 25μg/ml against these test organisms while MIC of Cassia occidental is ranged between 12.5μg/ml to 25μg/ml, while that of Eurporbia hirta  ranged between 25μg/ml and 50μg/ml. The Minimum Bactericidal Concentration (MBC) of Cassia occidentalis  and Euphorbia hirta was 25μg/ml for all the bacterial isolates, while that for Solanum americanum  was 12.5μg/ml for Pseudomonas aemginosa  and Staphlococcus aureus and 25μg/ml for E. coli and Klebsiella pneumoniae. Keywords : Antimicrobial activity, Medicinal plants, Minimum Bactericidal Concentration, Minimum Inhibitory Concentration