Antioxidant effects of extracts from Cassia tora L. prepared under different degrees of roasting on the oxidative damage to biomolecules

The effects of water extracts from Cassia tora L. (WECT) treated with diffe rent degrees of roasting (unroasted and roasted at 150, 200, and 250 degree s C) on the oxidative damage to deoxyribose, DNA, and DNA base in vitro wer e investigated. It was found that WECT alone induced a slight strand breaki ng of DNA. In the presence of Fe3+/H2O2, WECT accelerated the strand breaki ng of DNA at a concentration of 2 mu g/mL; however, it decreased with incre asing concentrations (>5 mu g/mL) of WECT. WECT also accelerated the oxidat ion of deoxyribose induced by Fe3+-EDTA/H2O2 at a concentration of 0.2 mg/m L but inhibited the oxidation of deoxyribose induced by Fe3+-EDTA/H2O2/asco rbic acid. Furthermore, WECT accelerated the oxidation of 2'-deoxyguanosine (2'-dG) to form 8-OH-2'-dG induced by Fe3+-EDTA/H2O2. The prooxidant actio n of WECT on the oxidation of 2'-dG was in the order of unroasted > roasted at 150 degrees C > roasted at 200 degrees C > roasted at 250 degrees C. Th e decrease in the prooxidant activity of the roasted sample might be due to the reduction in its anthraquinone glycoside content or the formation of a ntioxidant Maillard reaction products after roasting. Thus, WECT exhibited either a prooxidant or an antioxidant property in the model system that was dependent on the activities of the reducing metal ions, scavenging hydroxy l radical, and chelating ferrous ion.