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Effect of 3-O-Octanoyl-(+)-catechin on the Responses of GABA_A Receptors and Na⁺/Glucose Cotransporters Expressed in Xenopus Oocytes and on the Oocyte Membrane Potential

Hitoshi Aoshima,*^† Yoichi Okita,^† Sheikh Julfikar Hossain,^† Keiko Fukue,^† Mariko Mito,^† Yusuke Orihara,^† Terufumi Yokoyama,^‡ Mamoru Yamada,^‡ Ayako Kumagai,^§ Yasuo Nagaoka,^§ Shinichi Uesato,^§ and Yukihiko Hara

Department of Physics, Biology and Informatics, Faculty of Science, and Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8512, Japan, Department of Biotechnology, Faculty of Engineering, Kansai University, Suita, 564-8680 Osaka, Japan, and Mitsui Norin Company Limited, 3-2-11 Nishishinjuku, Shinjuku-Ku, Tokyo 160-8381, Japan

J. Agric. Food Chem., 2005, 53 (6), pp 1955–1959

DOI: 10.1021/jf048492c

Publication Date (Web): February 24, 2005

To whom correspondence should be addressed. Phone/fax: +81-83-933-5762. E-mail: aoshima@yamaguchi-u.ac.jp.

†

Faculty of Science, Yamaguchi University.

‡

Faculty of Agriculture, Yamaguchi University.

Kansai University.

Mitsui Norin Co. Ltd.

Abstract

Recently, 3-O-octanoyl-(+)-catechin (OC) was synthesized from (+)-catechin (C) by incorporation of an octanoyl chain into C in the light of (−)-epicatechin gallate (ECg) and (−)-epigallocatechin gallate (EGCg), which are the major polyphenols found in green tea and have strong physiological activities. OC was found to inhibit the response of ionotropic γ-aminobutyric acid (GABA) receptors (GABA_A receptors) and Na⁺/glucose cotransporters expressed in Xenopus oocytes in a noncompetitive manner more strongly than does C. OC also induced a nonspecific membrane current and decreased the membrane potential of the oocyte, and thus death of the oocyte occurred even at lower concentrations than that induced by C or EGCg. Although EGCg produced H₂O₂ in aqueous solution, OC did not. This newly synthesized catechin derivative OC possibly binds to the lipid membrane more strongly than does C, Ecg, or EGCg and as a result perturbs the membrane structure.

Keywords: Catechin; cell death; GABA_A, receptor; Na⁺/glucose cotransporter; Xenopus oocyte

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