The identification of flavonoids as glycosides in human plasma.

This study describes evidence for the absorption of flavonoids and their presence in human plasma in the glycosylated form by HPLC analysis with photodiode array detection. Rutin and other quercetin glycosides, phloridzin, as well as an anthocyanin are detected simultaneously. In addition, a compound eluting with the spectral properties of the aurone family is identified. The results reveal that phloretin and quercetin are absorbed from the diet as glycosides. The polyphenols are detected in plasma from non-supplemented humans at individual levels in the range 0.5-1.6 microM.