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Deglycosylation of flavonoid and isoflavonoid glycosides by human small intestine and liver beta-glucosidase activity.

Author(s): Baye G. Williamson, Daniel Dupont, David M. Rhodes, Gareth J. Morgan, S Ridley, Emily A. Day

Publication date: 1998-09-25

Keywords: Cell Extracts, Cell-Free System, Chamomile, Cytosol, enzymology, Flavanones, Flavonoids, metabolism, Genistein, Gluconates, pharmacology, Glycosides, Glycosylation, Humans, Inositol, analogs & derivatives, Intestine, Small, Isoflavones, Lactones, Liver, Oils, Volatile, Plants, Medicinal, Quercetin, Rutin, Taurocholic Acid, beta-Glucosidase, antagonists & inhibitors

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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 Km for hydrolysis of quercetin 4'-glucoside and genistein 7-glucoside was approximately 32+/-12 and approximately 14+/-3 microM in both tissues respectively. The enzymatic activity of the cell-free extracts exhibits similar properties to the cytosolic broad-specificity -glucosidase previously described in mammals.

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Most cited references 15

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Polyphenolic flavanols as scavengers of aqueous phase radicals and as chain-breaking antioxidants.

G Paganga, N Salah, G. Bolwell … (1995)

The purpose of this investigation was to establish the relative antioxidant activities in vitro of the flavanolic polyphenols, the catechins, and catechin-gallate esters. The relative antioxidant potentials were measured against radicals generated in the aqueous phase and against propagating lipid peroxyl radicals. The results show that in the aqueous phase their order of effectiveness as radical scavengers is epicatechin gallate (ECG) > epigallocatechin gallate (EGCG) > epigallocatechin (EGC) > gallic acid (GA) > epicatechin congruent to catechin; against propagating lipid peroxyl radical species, epicatechin and catechin are as effective as ECG and EGCG, the least efficacious being EGC and GA. This is consistent with their relative abilities to protect against consumption of LDL alpha-tocopherol. The results are discussed in the context of the most relevant antioxidant constituents of green tea extracts.