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

The metabolism of eriocitrin (eriodictyol 7-rutinoside), an antioxidant in lemon fruit (Citrus limon B-URM. 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 alpha-tocopherol. The activities of 3,4-DHCA and PHL were weak, but they preserved the antioxidative activity.