ASSESSING THE ANTIMICROBIAL PROPERTIES OF METHANOL EXTRACTS OF SELECTED NIGERIAN MEDICINAL PLANTS USING TETRAZOLIUM MICROPLATE ASSAY

Abstract

Medicinal plants have made significant contributions to the treatment of infectious diseases. An upsurge in antimicrobial resistance has caused an upsurge in the demand for the identification and development of novel antimicrobial agents. This study aimed to investigate the antimicrobial activity of methanol leaf extracts of viz; Deterium microcarpum Guill. & Perr, Lophira alata Banks ex Gaertn, Hibiscus tiliaceus L. and Ricinus communis L. The Minimal Inhibitory Concentration (MIC) values for the test microorganisms, Staphylococcus aureus (ATCC6571), Escherichia coli (ATCC25922), Pseudomonas aeruginosa (ATCC 27853), and Bacillus subtilis (ATCC3366), and isolates of Trichophyton rubrum and Candida albicans were determined using the modified rapid p-iodonitrotetrazolium chloride (INT) colorimetric assay. The antimicrobial activity of the extracts varied against all the test microorganisms, with MIC values ranging between 125.00-7.81µg/mL. Detarium microcarpum extract exhibited complete growth inhibition at the lowest extract concentration with a MIC value of 7.81 µg/mL on C. albican while Hibiscus tiliaceus and Ricinus communis had the highest growth inhibition on T. rubrum at the MIC value of 15.63 µg/mL. After subculturing, all the extracts displayed Minimum Fungicidal Concentration (MFC) ranged from 31.25-62.50 µg/mL on T. rubrum. Hibiscus tiliaceus, Detarium microcarpum and Lophira alata exhibited strong Minimum Bactericidal Concentration (MBC) on E. coli with an MBC value of 62.50 µg/mL. This study justifies the usage of these plants in ethnomedicine to treat a variety of infectious disorders, based on the broad-spectrum antimicrobial activity these plants have demonstrated. Keywords: Antimicrobial activity, p-Iodonitrotetrazolium chloride (PINT), antimicrobial resistance, Medicinal plants, Nigeria.