| Abstract
| - It was previously reported that (−)-epigallocatechin-3-O-gallate (EGCG) suppresses the expressionof the high-affinity IgE receptor FcεRI in human basophilic cells and that this suppressive effect isassociated with EGCG binding to the cell surface. This study examined the effects of five methylatedderivatives of EGCG, (−)-epigallocatechin-3-O-(3-O-methyl)gallate (EGCG 3‘ ‘Me), (−)-epigallocatechin-3-O-(4-O-methyl)gallate (EGCG 4‘ ‘Me), (−)-4‘-O-methyl-epigallocatechin-3-O-gallate (EGCG4‘Me), (−)-epigallocatechin-3-O-(3,4-O-methyl)gallate (EGCG 3‘ ‘4‘ ‘diMe), and (−)-4‘-O-methyl-epigallocatechin-3-O-(4-O-methyl)gallate (EGCG 4‘4‘ ‘diMe) on FcεRI expression and ERK1/2 phosphorylation, and each of their cell surface binding activities was measured. Of these five methylatedderivatives, three that are methylated at the 3‘ ‘- and/or 4‘ ‘-position, EGCG 3‘ ‘Me, EGCG 4‘ ‘Me, andEGCG 3‘ ‘4‘ ‘diMe, suppressed FcεRI expression and ERK1/2 phosphorylation, although the suppressive effects were lower than that of EGCG. EGCG 4‘Me and EGCG 4‘4‘ ‘diMe, both of which aremethylated at the 4‘-position, did not demonstrate a suppressive effect. Furthermore, it was foundthat EGCG 3‘ ‘Me, EGCG 4‘ ‘Me, EGCG 3‘ ‘4‘ ‘diMe, and EGCG 4‘Me, which are methylated at the 3‘ ‘-and/or 4‘ ‘-positions or the 4‘-position, could bind to the cell surface even though their binding activitieswere lower than that of EGCG. Only EGCG 4‘4‘ ‘diMe, which is methylated at both the 4‘- and 4‘ ‘-positions, could not bind. These results suggest that the trihydroxyl structure of the B ring is essentialfor EGCG to exert the suppressive effects and that the hydroxyl groups on both the 4‘-position in theB ring and the 4‘ ‘-position in the gallate are crucial for the cell surface binding activity of EGCG. Keywords: Methylated derivatives of EGCG; FcεRI; ERK1/2; cell surface binding activity
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