IN-VITRO ANTIOXIDANT AND FREE RADICAL SCAVENGING ACTIVITIES OF OCIMUM SANCTUM

The present study was carried out to evaluate the antioxidant and free radical scavenging activity of aqueous ethanolic (1:1) extract of Ocimum sanctum (AEOS) in various systems. DPPH radical, nitric oxide radical, superoxide anion radical and hydroxyl radical scavenging assays were carried out to evaluate the antioxidant potential of the extract. The antioxidant activity of aqueous ethanolic extract increased in a dose dependent manner. About 50, 100, 200, 300, 400 and 500 μg/mL of AEOS showed 38.06, 41.45, 44.83, 49.06, 57.78 and 65.98% inhibition respectively on peroxidation of linoleic acid emulsion. Like antioxidant activity, the effect of AEOS on reducing power increases in a dose dependent manner, indicating some compounds in Ocimum sanctum is both electron donors and could react with free radicals to convert them into more stable products and to terminate radical chain reactions. In DPPH radical scavenging assay the IC50 value of the extract was found to be 34.21μg/mL where as IC50 value of ascorbic acid was 18.69 μg/mL. AEOS was found to inhibit the nitric oxide radicals generated from sodium nitroprusside, the IC50 value was found to be 86.91 μg/mL, whereas the IC50 value of curcumin was 86.91 μg/mL. Moreover, the AEOS was found to scavenge the superoxide generated by PMS/NADH-NBT system. The IC50 value of extract was found to be 73.38 μg/mL whereas the IC50 value of curcumin was found to be 24.67 μg/mL. AEOS was also found to inhibit the hydroxyl radical generated by the deoxyribose method, the concentration of extract needed for 50% inhibition was found to be 42.69 μg/mL. Catechin, used as a standard, showing an IC50 value 17.71 μg/mL, which indicates the prooxidant activity of AEOS. The total phenolic and flavonoid content of Ocimum sanctum were also determined in this study and is found to be 82.02 ± 8.17 mg GAE/g and 74.6±5.1 mg/g respectively. The results obtained in the present study indicate that the AEOS can be a potential source of natural antioxidant.