Metabolism of antioxidant in lemon fruit (Citrus limon BURM. f.) by human intestinal bacteria

The metabolism of eriocitrin (eriodictyol 7-rutinoside), an antioxidant in lemon fruit (Citrus limon BURM. f.), was examined using intestinal bacteria. In the experiment, it was shown that eriocitrin was hydrolyzed to eriodictyol, its aglycon, by Bacteroides distasonis and Bacteroides uniformis. Eriodictyol was converted to 3,4-dihydroxyhydrocinnamic acid (3,4,-DHCA) and phloroglucinol (PHL) by Clostridium butyricum. The metabolic pathway of eriocitrin to eriodictyol and 3,4-DHCA was confirmed by using human feces. The antioxidative activity of eriocitrin metabolites, eriodictyol, 3,4-DHCA, and PHL, was examined using linoleic acid autoxidation and a rabbit erythrocyte membrane oxidation system. It was shown that eriodictyol exhibited stronger activity than α-tocopherol. The activities of 3,4-DHCA and PHL were weak, but they preserved the antioxidative activity. Keywords: Lemon fruit; Citrus limon; antioxidant; eriocitrin; flavanone; metabolism; intestinal bacteria