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Abstract-Background: Vernoniaamygdalina and Ocimumgratissimumare widely used plants in the tropics. The leaves of these plants are popularly acclaimed to have medicinal values, with scarce information on the effect of graded extracts in mediating oxidative stress. The interest on these leaves derives from the need to have an insight to the possible effect of thesegraded leaves extracts may have on oxidative stress. Objectives: The objective of the study was to examine the effect of graded extracts of Vernoniaamygdalina and Ocimumgratissimum leaves specifically on free radical inhibition, reducing power and lipid peroxidation in rat liver and kidneys. Methods: The leave samples were collected and air dried, homogenized and sieved to obtain particle sizes of ≤ 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 peroxidationin liver and kidneys were determined, using standard analytical assays. Results: Phenolic contents of both leave extracts were higher in aqueous medium vernoniaamygdalina (0.85 ± 0.07mgGAE/g) and Ocimumgratissimum (1.59 ± 0.13mgGAE/g). The alkaloid contents of the leaves were higher in methanolic extracts, with Ocimumgratissimum highest (0.96 ± 0.04μg/g) and vernoniaamygdalina (0.38 ± 0.01μg/g). The reducing power of these leaves increased with increasing extract concentrations. Ocimumgratissimum had the highest reducing power in both methanolic (3.00 O.D) and aqueous (2.82 O.D) medium in comparison with respective butylatedhydroxytoluene (BHT) (2.49 O.D) and ascorbic acid (2.16 O.D) controls. The ability to scavenge free radicals increased with increasing extract concentrations in both leaves with highest percentages in aqueous extracts.Ocimumgratissimum(95.90%) and vernoniaamygdalina(98.80%) compared to control (100%).The leave extracts of both plants significantly (p<0.05) increased lipid peroxidations in liver and kidneys of rats. Conclusion: Fresh leaves of Ocimumgratissimumand vernoniaamygdalinahave shown potentials to be valuable in reducing powers and free radical quenching.