Free radical scavenging and antigenotoxic activities of natural phenolic compounds in dried flowers of Hibiscus sabdariffa L.

The antioxidant and free radical scavenging effects of two fractions of the ethanolic extract (HSCF, chloroform soluble fraction and HSEA, ethyl acetate soluble fraction) obtained from the dried flowers of Hibiscus sabdariffa L were investigated. The total antioxidant activity of the extracts was estimated to be 4.6 and 8.6 mM of vitamin C for HSCF and HSEA, respectively. Both HSCF and HSEA scavenged hydrogen peroxide (H(2)O(2)) (79-94%) at the dose of 500 microg. Similarly, the extracts showed inhibitory (70-80%) effects on superoxide anions radicals (O(2) (- *)) at a dose of 1000 microg. The concentrations required for a 50% scavenging of hydroxyl radical (OH) (IC(50)) were 380 and 200 microg for HSCF and HSEA, respectively. HSEA and HSCF were better scavengers of O(2) (- *), *OH and H(2)O(2) as compared to BHA, quercetin and alpha-tocopherol. At a concentration of 25 microg/mL HSCF and HSEA exhibited 32 and 38% inhibition on CCl(4)-NADPH-induced lipid peroxidation, respectively, while both extracts exhibited 80 and 89% inhibitory effects at 100 microg/mL. Pretreatment with H. sabdariffa extracts orally with 100 mg/kg and 250 mg/kg simultaneously with intraperitoneal injection FeCl(2)-ascorbic acid-ADP mixture reduced (p < 0.01) the formation of malondialdehyde content. Treatment of rats with HSCF, HSEA and vitamin C (standard antioxidant) significantly inhibited the induction of micronucleated polychromatic erythrocytes by sodium arsenite (2.5 mg/kg) (p < 0.001) after 24 h by 60, 70 and 50%, respectively. The results indicate that extracts of H. sabdariffa showed strong antimutagenic activity and free radical scavenging effects on active oxygen species.