Isolation of C-Glucosylflavone from Lemon Peel and Antioxidative Activity of Flavonoid Compounds in Lemon Fruit

J. Agric. Food Chem., 45 (12), 4619 -4623, 1997. jf970498x S0021-8561(97)00498-6

Isolation of C-Glucosylflavone from Lemon Peel and Antioxidative Activity of Flavonoid Compounds in Lemon Fruit

Yoshiaki Miyake,* Kanefumi Yamamoto, Yasujiro Morimitsu, and Toshihiko Osawa

Central Research Laboratory of Pokka Corporation Ltd., 45-2 Kumanosyo, Shikatsu-cho, Nishikasugai-gun, Aichi, 481, Japan, and Department of Applied Biological Sciences, Nagoya University, Nagoya 464-01, Japan

Received for review June 13, 1997. Accepted October 1, 1997.

Abstract:

Two antioxidative two C-glucosylflavones were isolated from the peel of lemon fruit (Citrus limon B_URM. f.). They were identified as 6,8-di-C--glucosyldiosmin (LE-B) and 6-C--glucosyldiosmin (LE-C) by UV, IR, FAB-MS, ¹H NMR, and ¹³C NMR analyses. The antioxidative activities of LE-B, LE-C, and flavonoid compounds (eriocitrin, diosmin, hesperidin, and narirutin) in lemon fruit were examined using linoleic acid autoxidation, the liposome oxidation system, and the low-density lipoprotein (LDL) oxidation system. LE-B and LE-C showed antioxidative activity in these autoxidation systems but exhibited weaker activity than eriocitrin, its eriodictyol of its aglycon. Eriocitrin and its metabolites by intestinal bacteria (eriodictyol, 3,4-dihydroxyhydrocinnamic acid, and phloroglucinol) exhibited stronger antioxidative activity than -tocopherol in the LDL oxidation system and had approximately the same activity as (-)-epigallocatechin gallate. Eriocitrin and its metabolites are powerful antioxidants using an in vitro oxidation model for heart disease.

Keywords: Lemon fruit; Citrus limon; antioxidant; eriocitrin; flavonoid; 6,8-di-C--glucosyldiosmin; 6-C--glucosyldiosmin

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