| Abstract
| - Calf thymus DNA was oxidized by Fenton's reagent with or without synthetic antioxidants (Troloxand DMPO) and natural antioxidantsquercetin, apigenin, 2‘ ‘-O-glycosylisovitexin (2‘ ‘-O-GIV),(+)-catechin, cyanidin, pelargonidin, keracyanin, and callistephin. Malonaldehyde (MA) formed inoxidized DNA was analyzed using gas chromatography. MA formed from oxidized DNA without antioxidants was 4.0 ± 0.53 nmol/mg of DNA in buffer solution, 3.7 ± 0.34 nmol/mg of DNA in NaOHsolution, and 4.6 ± 0.19 nmol/mg of DNA in HCl solution. MA formed from DNA with antioxidants (atthe level of 0.1 μmol/mL) ranged from 1.90 ± 0.18 (catechin) to 4.10 ± 0.18 nmol/mg of DNA(cyanidin). Trolox and DMPO inhibited MA formation from DNA by 41.2% and 18.6%, respectively,at the level of 0.1 μmol/mL. Trolox (water-soluble vitamin E) exhibited dose-dependent inhibition. Thedecreasing order of inhibitory effect by flavonoids at the level of 0.1 μmol/mL was catechin (48.5%)> quercetin (47.1%) > 2‘ ‘-O-GIV (40.5%) > apigenin (29.9%) and by the anthocyanins at the levelof 0.1 μmol/mL was callistephin (45%) > keracyanin (33.2%) > pelargonidin (25.1%) > cyanidin (10.2%). Keywords: DNA; flavonoids; malonaldehyde; natural antioxidants; oxidative damage; Trolox
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