Screening of Vernonia amygdalina leaf extracts for antioxidant and antimicrobial activity

Abstract

Vernonia amygdalina (VA), a member of Asteraceae is one of the plants with medicinal properties. This present study was carried out to evaluate the antioxidant and antimicrobial properties of VA leaf extracts at various concentrations (20 mg/mL, 40 mg/mL, 60 mg/mL, 80 mg/mL, and 100 mg/mL) using petroleum ether, ethyl acetate and methanol solvent via soxhlet extraction method. The methanol extract (ME), ethyl acetate extract (EAE) and petroleum ether extract (PEE) were subjected to DPPH radical scavenging activity, ferric reducing antioxidant power activity (FRAP) total phenolic (TP) content, total flavonoid (TF) content assay, and antibiotic sensitivity test (AST). Results were analyzed using ANOVA. In DPPH assay, the ME shows significantly increased (90.11%) scavenging activity followed by EAE (64.12%) and PEE (37.39%). The ME has significantly higher absorbance (1.007) followed by EAE (0.664) and PEE (0.145) for FRAP assay. The TP content was significantly highest in ME (96.14 mg GAE/g extract) followed by EAE (95.18 mg GAE/g extract) and PEE (31.50 mg GAE/g extract). The TF content was 44.35, 42.52 and 15.16 mg QE/g extract for ME, EAE, and PEE respectively. The AST demonstrates S.aureus sensitive towards ME, EAE and PEE. The E. faecalis were sensitive towards ME and EAE. Both P.aeruginosa and E.coli were resistant towards all of the crude extracts. ME contains highest antioxidant and antimicrobial activity which increases with concentration.