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Transformation of flavonoids by intestinal microorganisms

Blaut M, Schoefer L, Braune A

International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition, 2003

Abstract

Fruit, vegetables and cereals contain a wealth of secondary plan metabolites which have been implicated in the promotion of health. To understand the mechanism of their action it is necessary to gain more information on their fate in the body following ingestion. A certain proportion of ingested secondary plant constituents may escape absorption in the small intestine and therefore undergo transformation by intestinal microorganisms or enterohepatic circulation. To study the transformation of secondary plant metabolites by bacteria, Eubacterium ramulus was isolated from human feces and incubated with selected flavonoids. E. ramulus is a strictly anaerobic bacterium which was found to be present in the gastrointestinal tract of most individuals investigated. E. ramulus cleaves the ring system of several flavonols and flavones giving rise to the corresponding hydroxyphenylacetic and hydroxyphenylpropionic acids, respectively, as well as acetate and butyrate. Degradation pathways were proposed based on the intermediates detected by high performance liquid chromatography (HPLC) and HPLC coupled with mass spectrometry (LC-MS) and the detection of enzymes that catalyze reactions such as taxifolin isomerization, phloretin hydrolysis and phloroglucinol reduction. The dearomatizing phloroglucinol reductase, presumably part of all flavonoid degradation pathways, was purified and characterized. The gene encoding phloretin hydrolase was cloned from a E. ramulus gene library taking…

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