Study on antimicrobial and antioxidant potentials of Alchornea cordifolia (Linn.): an in vitro assessment

This study investigated antimicrobial properties of Alchornea cordifolia leaf extract against a panel of selected bacterial strains. It also assessed antioxidant and phytochemical properties of the plant constituents responsible for the bioactive actions recorded. The antimicrobial potentials of the crude extract along with the fractions obtained were determined using the agar well-diffusion method. The most active fraction was partially purified by a combination of thin-layer and column chromatography; and the antimicrobial activity of the resulting samples was tested against the bacterial strains. The results showed that the leaf extract of A. cordifolia and the obtained fractions exhibited varying degrees of antibacterial activities. Phytochemical tests revealed the presence of alkaloids, flavonoids, tannins, saponins, phenols, resins, sterols, carbohydrates and terpenoids. The minimum inhibitory concentrations of the crude extracts were 0.55–4.38 mg/mL while those of the chloroform and ethyl acetate fractions were 0.08–2.50 and 0.08–0.63 mg/mL, respectively. The rate of kill assay showed that the percentage of cells killed was related to concentrations and contact time. The nucleotide and potassium ion leakage from test cells also increased with an increase in the fraction concentrations as well as the contact time intervals. Alchornea cordifolia extract exhibited 50% 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities at 2.1 µg/mL, whereas the ascorbic acid used as standard had a half maximal inhibitory concentration (IC50) of 12.3 µg/mL. The major active constituent of the purified sample was 6-octadecanoic acid. This study showed that A. cordifolia leaf extract, which possesses antioxidant properties, exhibited significant antimicrobial activities against the test pathogens.