Absorption, metabolism and health effects of dietary flavonoids in man

摘要: Summary Flavonoids are polyphenolic compounds that occur ubiquitously in foods of plant origin. Over 4,000 different flavonoids have been described, and they categorized into flavonols, flavones, catechins, flavanones, anthocyanidins isoflavonoids. a variety biological effects numerous mammalian cell systems, vitro as well vivo. Recently, much attention has paid to their antioxidant properties inhibitory role various stages tumour development animal studies. Quercetin, the major representative flavonol subclass, is strong antioxidant, prevents oxidation low density lipoproteins vitro. Oxidized atherogenic, considered be crucial intermediate formation atherosclerotic plaques. This agrees with observations epidemiological studies intake flavonols flavones was inversely associated subsequent coronary heart disease. However, no on cancer were found these The extent absorption an important unsolved problem judging many alleged health effects. present non-absorbable because bound sugars s-glycosides. Only free without sugar molecule, so-called aglycones, thought able pass through gut wall. Hydrolysis only occurs colon by microorganisms, which at same time degrade flavonoids. We performed study quantify dietary forms quercetin. To our surprise, quercetin glycosides from onions absorbed far better than pure aglycone. Subsequent pharmacokinetic showed marked differences rate bioavailability. Absorbed eliminated slowly blood. metabolism studied frequently animals, but very few data humans available. Two sites flavonoid liver colonic flora. There evidence for O-methylation, sulphation glucuronidation hydroxyl groups liver. Bacterial ring fission colon. degradation products, phenolic acids, can urine animals. Quantitative scarce.