Introduction: The plant, Vernonia amygdalina is a tropical plant commonly used in the treatment of ailments locally because it is assumed that it possesses medicinal properties. Objective: The mediating role of its leaf extract in ameliorating oxidative stress is thus explored in this investigation. Methods: The leave samples were collected, air dried, homogenized and sieved to obtain particle sizes of â‰¤ 0.250mm. Aqueous and methanolic extracts of samples were obtained and used to assay for total alkaloid and phenolic contents, free radical scavenging activity, reducing power and the extent of lipid peroxidation in liver and kidneys were determined. Standard analytical methods were used in all assays. Results: Free radicals inhibitions and reducing powers of extracts were found to increase with increasing extracts concentrations, with highest inhibitions obtained as 98.80 ± 6.45 and 77.99 ± 6.34% in aqueous and methanol, as against 100.00 ± 0.00% respective controls of ascorbic acid and Butylated Hydroxytoluene (BHT). Reducing powers of extracts increased with progressive increases in extracts concentrations, with 1.23 ± 6.34mgRE/g for aqueous and 0.53 ± 0.04mgRE/g in methanol, as compared with respective controls of 2.13 ± 0.04 and 2.49 ± 0.03 respectively. The inhibitory concentrations (IC50) for aqueous and MeOH extracts are 2.0mg/mL and 2.3mg/mL respectively. For reducing power, it was 4.2mgRE/g and 2.2mgRE/g respectively, as against 2.8 mgRE/g and 2.96mgRE/g for Vit C and BHT controls respectively. The leave extracts of Vernonia amygdalina significantly (p
Bitter leaf, free radicals, lipid peroxidation.