Deglycosylation of flavonoid and isoflavonoid glycosides by human small intestine and liver β‐glucosidase activity

Flavonoid and isoflavonoid glycosides are common dietary phenolics which may be absorbed from the small intestine of humans. The ability of cell‐free extracts from human small intestine and liver to deglycosylate various (iso)flavonoid glycosides was investigated. Quercetin 4′‐glucoside, naringenin 7‐glucoside, apigenin 7‐glucoside, genistein 7‐glucoside and daidzein 7‐glucoside were rapidly deglycosylated by both tissue extracts, whereas quercetin 3,4′‐diglucoside, quercetin 3‐glucoside, kaempferol 3‐glucoside, quercetin 3‐rhamnoglucoside and naringenin 7‐rhamnoglucoside remained unchanged. The K m for hydrolysis of quercetin 4′‐glucoside and genistein 7‐glucoside was ∼32±12 and ∼14±3 μM in both tissues respectively. The enzymatic activity of the cell‐free extracts exhibits similar properties to the cytosolic broad‐specificity β‐glucosidase previously described in mammals.

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