Inhibitory Effects of the C-2 Epimeric Isomers of Tea Catechins on Mouse Type IV Allergy

The inhibitory effects of C-2 epimeric isomers of (-)-epigallocatechin-3-O-gallate (EGCG) and two O-methylated EGCG derivatives, (-)-epigallocatechin-3-O-(3-O-methyl)gallate (EGCG3''Me) and (-)-epigallocatechin-3-O-(4-O-methyl)gallate (EGCG4''Me), against oxazolone-induced type IV allergy in male mice were investigated. These compounds exhibited strong antiallergic effects by percutaneous administration at a dose of 0.13 mg/ear. The inhibition rates of (-)-gallocatechin-3-O-gallate (GCG), (-)-gallocatechin-3-O-(3-O-methyl)gallate (GCG3''Me), and (-)-gallocatechin-3-O-(4-O-methyl)gallate (GCG4''Me) on mouse type IV allergy were 52.1, 53.3, and 54.8%, respectively. However, the antiallergic effects were weaker than those of their corresponding original tea catechins (2R,3R type). The inhibition rates of those were 88.0, 73.2, and 77.6%, respectively. For all of the catechins tested, oral administration at a dose of 50 mg/kg body weight significantly suppressed the allergic symptoms. The inhibitory rates varied from 24.0 to 60.6%. No significant differences were observed between the effects of the epimers (2S,3R type) and their corresponding original catechins (2R,3R type). The antiallergic effects of tea catechins and their C-2 epimers observed in this study were dose-dependent. These results suggest that C-2 epimers of tea catechins, which are produced during heat processing at high temperatures, could be disadvantageous for the antiallergic effects on type IV allergy.