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

TLDR

Flavonoid and isoflavonoid glycosides are common dietary phenolics that can be absorbed in the human small intestine. The study examined whether cell‑free extracts from human small intestine and liver can deglycosylate various (iso)flavonoid glycosides. Both tissues rapidly deglycosylated quercetin 4′‑glucoside, naringenin 7‑glucoside, apigenin 7‑glucoside, genistein 7‑glucoside and daidzein 7‑glucoside, but left quercetin 3,4′‑diglucoside, quercetin 3‑glucoside, kaempferol 3‑glucoside, quercetin 3‑rhamnoglucoside and naringenin 7‑rhamnoglucoside unchanged; Km values were ~32 µM for quercetin 4′‑glucoside and ~14 µM for genistein 7‑glucoside, indicating activity similar to mammalian cytosolic broad‑specificity β‑glucosidase.

Abstract

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.