Evaluation of Selected Nigerian Medicinal Plants for Phenolic Content, Antimicrobial, and Cytotoxic Activities

Abstract

Evaluation of Selected Nigerian Medicinal Plants for Phenolic Content, Antimicrobial, and Cytotoxic Activities. Abstract Increased exposure to pathogens and free radicals contributes to the high incidence and mortality rate of various types of cancers in Nigeria and globally. This study aimed to screen twenty extracts from fifteen selected Nigerian medicinal plants used traditionally for cancer treatment for phenolic content, antimicrobial, and cytotoxic activities. The phenolic content was determined by Folin – Ciocalteu method, and antimicrobial potentials of the extracts was evaluated using spectrophotometric growth inhibition method while MTT assay was used to assess their cytotoxicity to cancer cell lines. Bark and root extracts of T. tetraptera and X. aethiopica demonstrated satisfactory activities in all the biological tests, which could be linked to their high phenolic contents. The findings support the ethnomedicinal uses of most of the tested medicinal plants. The antimicrobial study showed that the extracts exhibit inhibitory activity against tested bacterial and fungal strains (Table 3). The root and bark extracts of X. aethiopica and leaf extracts of A. difformis, Morinda lucida , and Pterocarpus osun had IC 50 of 1.5, 20.0, 3.8, 16.9, and 4.1 against Salmonella typhi. Similarly, A. difformis and bark extract of X. aethiopica produced comparable activities against E. coli . All tested extracts were active against Pseudomonas aeruginosa ; however, none was comparable (P<0.05) to the activity of Streptomycin with IC 50 of 0.9 µg mL -1 . Root extracts of X. aethiopica and leaf extract of A. difformis showed a broad spectrum of antibacterial activities. Antifungal studies against Candida albicans showed that root extracts of C. retusa, T. tetraptera , and Ketoconazole exhibited comparable (P<0.05) antifungal activities.