In Vitro Evaluation of Antioxidant and Free Radical Scavenging Activities of Rhodiola imbricata

The present study was undertaken to evaluate the in vitro antioxidant activities of aqueous extract of Rhodiola imbricata rhizome. The plant extract was evaluated for DPPH (1,1-diphenyl, 2-picryl hydrazyl) radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, anti-lipid peroxidation assay, metal chelating activity, reducing power and total flavonoid content. Rhodiola imbricata aqueous extract (RIAE) exhibited more DPPH scavenging potential with IC50 value of 5.56 µg/ml as compared to standard butylated hydroxytoluene (BHT) (IC50 = 5.74 µg/ml). The extract also provided superoxide anion radicals' scavenging (IC50 = 4.68 vs 4.63 µg/ml) and anti-lipid per-oxidation activity (IC50 = 5.06 vs 4.91 µg/ml) and IC50 value was comparable to standard ?-tocopherol. The RIAE showed a decrease in hydrogen peroxide generation with IC50 value of 3.25 µg/ml when compared with standard ?-tocopherol (IC50 value=4.00 µg/ml). IC50 of the extract for chelating activity was 5.33 ?g/ml which was lower than the positive standard quercetin (IC50 = 3.12 ?g/ml) but higher than ?-tocopherol (IC50 = 6.13 ?g/ml). The reducing capability of extract increased in dose dependent manner. Flavonoid content of RIAE determined spectrophotometrically in terms of Quercetin equivalent was 66.7µg/mg. The results obtained in the present study indicated that aqueous extract of root of Rhodiola imbricata is a potent source of natural antioxidant.