1985 Volume 59 Issue 2 Pages 129-134
Instant green tea was extracted with chloroform and ethyl acetate to obtain a crude catechin mixture. The four main tea catechin components (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg) and (-)-epigallocatechin gallate (EGCg) were isolated from the crude catechin by HPLC and purified. The antioxidative effects of the four catechins were tested by the active oxygen method (AOM) at 97.8°C on lard. The antioxidative activity increased in molarity in the following order: EC<ECg<EGC<EGCg. This implies that their activities were related to their structural formula.
The synergism of EGCg with 19 amino acids, several organic acids and tocopherol was tested on lard by AOM at 97.8°C or 60°C. Among amino acids tested only L-methionine showed slight synergism, whereas most of the others showed accelerated oxidation. Tocopherol and several organic acids including L-ascorbic acid showed a remarkable synergistic effect. EGCg also acted as an antioxidant in the linoleic acid system but its activity was milder than in the lard system. In addition, the antioxidative activity of EGCg was demonstrated in a system where linoleic acid was solubilized in a large amount of water. EGCg had an antioxidative activity in both the oil and aqueous system. The crude catechin mixture showed a similar antioxidative effect as EGCg in the lard system and was also effective in commercial salad oil.