Antioxidant properties of water extracts from Cassia tora L. in relation to the degree of roasting

The antioxidant properties of water extracts from Cassia tora L. (WECT) pre pared under different degrees of roasting were investigated. The water extr acts of unroasted C. tora L. (WEUCT) showed 94% inhibition of peroxidation of linoleic acid at a dose of 0.2 mg/mL, which was higher than that of alph a-tocopherol (82%). Water extracts prepared from C. tora L. roasted at 175 degrees C for 5 min and at 200 degrees C for 5 min exhibited 83% and 2%, re spectively, inhibition of linoleic acid peroxidation. This result indicated that the antioxidant activities of WECT decreased with longer roasting tim e or higher roasting temperature. The IC50 Of WEUCT in liposome oxidation i nduced by the Fenton reaction was 0.41 mg/mL, which was higher than that of alpha-tocopherol (IC50 = 0.55 mg/mL). WEUCT also exhibited good antioxidan t activity in enzymatic and nonenzymatic microsome oxidative systems. The w ater extracts of roasted C. tora IL. increased in the degree of browning an d produced chemiluminescence when compared with the unroasted sample. Howev er, the total polyphenolic compounds of WECT decreased after the roasting p rocess finished. In conclusion, the decrease in the antioxidant activity of water extracts from roasted C. tora L. might have been due to the degradat ion of Maillard reaction products and the decrease of polyphenolic compound s.