EVALUATION OF ANTIOXIDANT PROPERTIES OF SOME MEDICINAL PLANTS BY SULFUR FREE RADICAL REACTIVITY WITH CURCUMIN AS REFERENCE

Curcumin, the chrome orange-yellow coloring compound present in turmeric rhizomes, has long been known to possess antioxidant property. Crude methanol extracts of five medicinal plant species-Mimosa pudica, Vitex trifolia, Centella asiatica, Leucas aspera, and Plantago major were evaluated for their antioxidant properties using sulfur free radical reactivity with curcumin as reference indicator. Sulfur free radicals (GS) are generated by irradiating 15 mM glutathione (GSH) solution using a 5100Ci cobalt-60 gamma irradiator. As reference indicator for the reactivity with sulfur free radicals, we used the depletion of pure curcumin sample in vitro as determined by a simple spectrophotometric method. The addition of the supernatant from the plant extracts to the reaction mixture significantly decreased the depletion of curcumin, indicating that these extracts possessed antioxidant properties. The relative curcumin protection by different plant extracts against GS showed that L. aspera gave highest degree of radio protection. Our result shows the potential use of these plant parts as herbal medicine.