ANTIOXIDANT ACTIVITY OF GREEN TEAS IN DIFFERENT LIPID SYSTEMS

Different commercial green teas from Japan, China, and India, were com pared in different lipid systems. Green teas were active antioxidants in bulk corn oil oxidized at 50 degrees C but were prooxidant in the c orresponding oil-in-water emulsions. Green teas also were active antio xidants in soybean lecithin liposomes oxidized at 37 degrees C in the presence of cupric acetate as catalyst. At 50 degrees C, however, thre e of the samples of green tea were active antioxidants in the absence of copper catalyst, and two samples showed prooxidant activity in the presence of copper catalyst. The marked variation in activity among gr een tea samples may be due partly to differences in their relative par tition between phases in different lipid systems. The improved antioxi dant activity observed for green teas in lecithin liposomes compared t o corn oil emulsions can be explained by the greater affinity of the p olar tea catechin gallates for the polar surface of the lecithin bilay ers, thus affording better protection against oxidation. Liposomes may thus be appropriate lipid models to evaluate antioxidants for foods c ontaining phospholipids.