Comparative antibacterial efficacies of the extracts of <i>Enantia chlorantha</i> (Awopa) on selected clinical isolates

Abstract

Researchers and health scientists are challenged by the phenomenon of antimicrobial resistance which has necessitated the need for the  discovery of novel antimicrobial agents. This study evaluated the antimicrobial efficacy of the bark of Enantia chlorantha (Awopa) based  on extractions using selected polar and non-polar solvents (Aqueous, Dichloromethane, Petroleum ether, and N-hexane). Antimicrobial  activities were investigated against six clinical isolates (Candida albicans, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus,  Streptococcus pneumoniae, and Pseudomonas aeruginosa) via the agar well diffusion assay. Minimum inhibitory concentration (MIC)  and Minimum Bactericidal Concentration (MBC) were also determined by the macro broth dilution method. The phytochemical  components of the extracts were analyzed qualitatively and quantitatively. The dichloromethane extract of E. chlorantha expressed the  highest antimicrobial activity against all the test organisms with K. pneumonia being the most susceptible with (21.50 mm zone of inhibition) at a concentration of 50mg/mL; while C. albicans was the least susceptible organism with 3.00 mm zone of inhibition at concentration of 500mg/mL. On the other hand, extract from the petroleum ether expressed no antimicrobial activities, based on the absence of the zones of inhibition around the cultures of the respective organisms. Mainly the Dichloromethane and aqueous extracts of  E. chlorantha expressed varying organism-dependent MIC on the test isolates. While the lowest MIC of dichloromethane extract was  expressed on S. aureus at 6.25mg/mL; the highest MIC (50mg/mL) was exerted on C. albicans. Phytochemical screening of the extracts  revealed the presence of glycosides, oxalates, steroids, alkaloids, tannins, flavonoids, phenol, triterpenes, saponin and phytate; while  terpenoid was not found in all the plant’s extracts. Findings in this study suggest that the bioactive ingredients of E. chlorantha barks  could be best extracted by polar solvents which are evident in the superior antimicrobial activities of dichloromethane and aqueous  extracts. The non-polar solvents such as n-hexane and petroleum ether are poor extractant, thus necessitating the need to carefully  select suitable solvent for the extraction of any plant’s bioactive compounds.