Effect of Roasting Process on the Antioxidant Properties of Cassia tora L

The antioxidant properties of water extracts from Cassia tora L. prepared under different degrees of roasting were investigated. The water extracts of Cassia tora showed inhibition of peroxidation of linoleic acid, which was higher than that of a-tocopherol. It exhibited good antioxidant activity in liposome oxidation induced by Fenton reaction as well as in enzymatic microsome oxidative systems. It also inhibited the oxidative DNA damage in human lymphocytes, induced by hydrogen peroxide as evaluated by the comet assay. However, the antioxidant activities of water extracts of Cassia tora decreased with higher roasting temperature or longer roasting time. The water extracts of roasted Cassia tora increased in the degree of browning and produced chemiluminescence when compared with the unroasted sample. The total polyphenolic compounds and anthraquinones of extracts of Cassia tora decreased after the roasting process finished. In conclusion, the decrease in the antioxidant activity of water extracts from roasted Cassia tora might have been due to the decrease of polyphenolic compounds and the degradation of Maillard reaction products.