Free radical damage was believed to be an important cause of aging. Various flavonoids were shown to be free radical scavengers and antioxidants. The wide distribution of flavonoids in plant kingdom prompts us to search for anti-aging agents from Chinese herbs. Naringin, hesperidin and rutin are flavonoid glycosides which are major constituents of herbs, e. g. zhiquor, chenpee and huaihua. This study investigated the absorption and metabolism of those three glycosides and their aglycones as pure compounds and from herbal decoctions. HPLC method was used to assay the serum and urine concentrations of the parent compounds and their metabolites. Our results indicated that the flavonoid glycosides were hydrolyzed by microflora in gut lumen into aglycones which is the absorbable form. During the first pass through gut wall, conjugation metabolism occurred appreciably. The pharmacokinetic parameters were calculated by using WINNONLIN. The absorption of these three flavonoids glycosides was quite low, especially for hesperidin. Most of the absorbed flavonoids circulate as glucuronides in the body. There was significant enterohepatic recycling. We suggested that preformulation study of these flavonoid glycosides were needed in order to enhance their absorption and efficacy.
