Quercetin

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Peter C H Hollman - One of the best experts on this subject based on the ideXlab platform.

  • Quercetin Glucuronides but Not Glucosides Are Present in Human Plasma after Consumption of Quercetin-3-Glucoside or Quercetin-4′-Glucoside
    The Journal of Nutrition, 2018
    Co-Authors: Aloys L A Sesink, Karen A. O'leary, Peter C H Hollman
    Abstract:

    The nature of Quercetin conjugates present in blood after consumption of Quercetin glucosides is still unclear. In this study, we analyzed plasma of volunteers that had consumed 325 micromol of either Quercetin-3-glucoside or Quercetin-4'-glucoside as an oral solution. Quercetin metabolites were extracted with acetonitrile/phosphoric acid and these extracts were analyzed using a high performance liquid chromatography with Coularray detection that distinguishes between the glucuronidated and the glucosylated forms of Quercetin. No intact Quercetin glucosides and only trace amounts of aglycone were found in human plasma, irrespective of the glucoside ingested. This was confirmed by spiking the plasma with glucoside standards. The major components in plasma had the same retention time as Quercetin glucuronide standards. These plasma components disappeared after treatment of the plasma with bovine liver beta-glucuronidase, under reformation of Quercetin, and showed the same oxidation pattern as the glucuronides. These results suggest that after consumption of Quercetin glucosides, Quercetin glucuronides are major metabolites in plasma.

  • supplementation of the pure flavonoids epicatechin and Quercetin affects some biomarkers of endothelial dysfunction and inflammation in pre hypertensive adults a randomized double blind placebo controlled crossover trial
    Journal of Nutrition, 2015
    Co-Authors: James I Dower, Daan Kromhout, Lieke Gijsbers, Casper G Schalkwijk, Johanna M. Geleijnse, Peter C H Hollman
    Abstract:

    Background Consumption of flavonoid-rich foods such as cocoa and tea may reduce cardiovascular disease risk. The flavonoids epicatechin (in cocoa and tea) and Quercetin (in tea) probably play a role by reducing endothelial dysfunction and inflammation, 2 main determinants of atherosclerosis. Objective We studied the effects of supplementation of pure epicatechin and Quercetin on biomarkers of endothelial dysfunction and inflammation. Methods Thirty-seven apparently healthy (pre)hypertensive men and women (40-80 y) participated in a randomized, double-blind, placebo-controlled crossover trial. Participants ingested (-)-epicatechin (100 mg/d), Quercetin-3-glucoside (160 mg/d), or placebo capsules for a period of 4 wk, in random order. Plasma biomarkers of endothelial dysfunction and inflammation were measured at the start and end of each 4-wk intervention period. The differences in changes over time between the intervention and placebo periods (Δintervention - Δplacebo) were calculated and tested with a linear mixed model for repeated measures. Results Epicatechin changed Δepicatechin - Δplacebo for soluble endothelial selectin (sE-selectin) by -7.7 ng/mL (95% CI: -14.5, -0.83; P = 0.03) but did not significantly change this difference (-0.30; 95% CI: -0.61, 0.01; P = 0.06) for the z score for endothelial dysfunction. Quercetin changed ΔQuercetin - Δplacebo for sE-selectin by -7.4 ng/mL (95% CI: -14.3, -0.56; P = 0.03), that for IL-1β by -0.23 pg/mL (95% CI: -0.40, -0.06; P = 0.009), and that for the z score for inflammation by -0.33 (95% CI: -0.60, -0.05; P = 0.02). Conclusions In (pre)hypertensive men and women, epicatechin may contribute to the cardioprotective effects of cocoa and tea through improvements in endothelial function. Quercetin may contribute to the cardioprotective effects of tea possibly by improving endothelial function and reducing inflammation. This trial was registered at clinicaltrials.gov as NCT01691404.

  • Tissue Distribution of Quercetin in Rats and Pigs
    Journal of Nutrition, 2005
    Co-Authors: Vincent C. J. De Boer, Siegfried Wolffram, Ilja C W Arts, Ashwin A. Dihal, Hester Van Der Woude, Gerrit M. Alink, Ivonne M.c.m. Rietjens, Jaap Keijer, Peter C H Hollman
    Abstract:

    Quercetin is a dietary polyphenolic compound with potentially beneficial effects on health. Claims that Quercetin has biological effects are based mainly on in vitro studies with Quercetin aglycone. However, Quercetin is rapidly metabolized, and we have little knowledge of its availability to tissues. To assess the long-term tissue distribution of Quercetin, 2 groups of rats were given a 0.1 or 1% Quercetin diet [∼50 or 500 mg/kg body weight (wt)] for 11 wk. In addition, a 3-d study was done with pigs fed a diet containing 500 mg Quercetin/kg body wt. Tissue concentrations of Quercetin and Quercetin metabolites were analyzed with an optimized extraction method. Quercetin and Quercetin metabolites were widely distributed in rat tissues, with the highest concentrations in lungs (3.98 and 15.3 nmol/g tissue for the 0.1 and 1% Quercetin diet, respectively) and the lowest in brain, white fat, and spleen. In the short-term pig study, liver (5.87 nmol/g tissue) and kidney (2.51 nmol/g tissue) contained high concentrations of Quercetin and Quercetin metabolites, whereas brain, heart, and spleen had low concentrations. These studies have for the first time identified target tissues of Quercetin, which may help to understand its mechanisms of action in vivo. © 2005 American Society for Nutritional Sciences.

  • the type of sugar moiety is a major determinant of the small intestinal uptake and subsequent biliary excretion of dietary Quercetin glycosides
    British Journal of Nutrition, 2004
    Co-Authors: Ilja C W Arts, Aloys L A Sesink, Maria Faassenpeters, Peter C H Hollman
    Abstract:

    Quercetin is an important dietary flavonoid with putative beneficial effects in the prevention of cancer and CVD. The in vivo bioactivity of Quercetin depends on its bioavailability, which varies widely between foods. We used an in situ rat intestinal perfusion model to study whether differential small intestinal hydrolysis of the sugar moiety of five naturally occurring Quercetin glycosides determines the small intestinal uptake and subsequent biliary excretion of Quercetin. After 30 min perfusion, a decrease of intact Quercetin glycoside in perfusate was observed for Quercetin-3-O-s-glucoside (20·9 (SEM 1·4) mmol/l) and Quercetin-4 0 -O-s-glucoside (23·5 (SEM 1·6) mmol/ l), but not of Quercetin-3-O-s-galactoside, Quercetin-3-O-s-rhamnoside and Quercetin-3-O-a-arabinopyranoside. Appearance of free Quercetin in perfusate and conjugated Quercetin metabolites (Quercetin, isorhamnetin, and tamarixetin) in portal and peripheral plasma and bile were also significantly greater after treatment with Quercetin-3-O-s-glucoside or Quercetin-4 0 -O-s-glucoside compared with any of the other glycosides. Thus, the type of sugar moiety is a major determinant of the small intestinal absorption of Quercetin glycosides, but the position (3 or 4 0 ) of the glucose moiety does not further influence absorption. The poor bioavailability of important dietary Quercetin glycosides has implications for their in vivo bioactivities. Flavonoid: Quercetin glycoside: Intestinal absorption: Lactase phlorizin hydrolase: Bile

  • Bioavailabilities of Quercetin-3-glucoside and Quercetin-4'-glucoside do not differ in humans.
    The Journal of nutrition, 2000
    Co-Authors: Margreet R Olthof, Peter C H Hollman, Tom B. Vree, Martijn B. Katan
    Abstract:

    The flavonoid Quercetin is an antioxidant which occurs in foods mainly as glycosides. The sugar moiety in Quercetin glycosides affects their bioavailability in humans. Quercetin-3-rutinoside is an important form of Quercetin in foods, but its bioavailability in humans is only 20% of that of Quercetin-4'-glucoside. Quercetin-3-rutinoside can be transformed into Quercetin-3-glucoside by splitting off a rhamnose molecule. We studied whether this 3-glucoside has the same high bioavailability as the Quercetin-4'-glucoside. To that end we fed five healthy men and four healthy women (19-57 y) a single dose of 325 micromol of pure Quercetin-3-glucoside and a single dose of 331 micromol of pure Quercetin-4'-glucoside and followed the plasma Quercetin concentrations. The bioavailability was the same for both Quercetin glucosides. The mean peak plasma concentration of Quercetin was 5.0+/-1.0 micromol/L (+/-SE) after subjects had ingested Quercetin-3-glucoside and 4.5+/-0.7 micromol/L after Quercetin-4'-glucoside consumption. Peak concentration was reached 37 +/-12 min after ingestion of Quercetin-3-glucoside and 27+/-5 min after Quercetin-4'-glucoside. Half-life of elimination of Quercetin from blood was 18.5+/-0.8 h after ingestion of Quercetin-3-glucoside and 17.7+/-0.9 h after Quercetin-4'-glucoside. We conclude that Quercetin glucosides are rapidly absorbed in humans, irrespective of the position of the glucose moiety. Conversion of Quercetin glycosides into glucosides is a promising strategy to enhance bioavailability of Quercetin from foods.

Martijn B. Katan - One of the best experts on this subject based on the ideXlab platform.

  • Bioavailabilities of Quercetin-3-glucoside and Quercetin-4'-glucoside do not differ in humans.
    The Journal of nutrition, 2000
    Co-Authors: Margreet R Olthof, Peter C H Hollman, Tom B. Vree, Martijn B. Katan
    Abstract:

    The flavonoid Quercetin is an antioxidant which occurs in foods mainly as glycosides. The sugar moiety in Quercetin glycosides affects their bioavailability in humans. Quercetin-3-rutinoside is an important form of Quercetin in foods, but its bioavailability in humans is only 20% of that of Quercetin-4'-glucoside. Quercetin-3-rutinoside can be transformed into Quercetin-3-glucoside by splitting off a rhamnose molecule. We studied whether this 3-glucoside has the same high bioavailability as the Quercetin-4'-glucoside. To that end we fed five healthy men and four healthy women (19-57 y) a single dose of 325 micromol of pure Quercetin-3-glucoside and a single dose of 331 micromol of pure Quercetin-4'-glucoside and followed the plasma Quercetin concentrations. The bioavailability was the same for both Quercetin glucosides. The mean peak plasma concentration of Quercetin was 5.0+/-1.0 micromol/L (+/-SE) after subjects had ingested Quercetin-3-glucoside and 4.5+/-0.7 micromol/L after Quercetin-4'-glucoside consumption. Peak concentration was reached 37 +/-12 min after ingestion of Quercetin-3-glucoside and 27+/-5 min after Quercetin-4'-glucoside. Half-life of elimination of Quercetin from blood was 18.5+/-0.8 h after ingestion of Quercetin-3-glucoside and 17.7+/-0.9 h after Quercetin-4'-glucoside. We conclude that Quercetin glucosides are rapidly absorbed in humans, irrespective of the position of the glucose moiety. Conversion of Quercetin glycosides into glucosides is a promising strategy to enhance bioavailability of Quercetin from foods.

  • Bioavailability of the dietary antioxidant flavonol Quercetin in man.
    Cancer letters, 1997
    Co-Authors: Peter C H Hollman, John M.p. Van Trijp, Marcel J.b. Mengelers, J H De Vries, Martijn B. Katan
    Abstract:

    Quercetin, a dietary antioxidant flavonoid, has anticarcinogenic properties. We quantified the absorption of Quercetin in ileostomists. Absorption was 52 +/- 5% for Quercetin glucosides from onions, 17 +/- 15% for Quercetin rutinoside, and 24 +/- 9% for Quercetin aglycone. The plasma Quercetin concentration in subjects with an intact colon, after ingestion of fried onions, apples and pure Quercetin rutinoside, decreased slowly with elimination half-lives of about 25 h. Thus, repeated dietary intake of Quercetin will lead to accumulation in plasma. The relative bioavailability of Quercetin from apples and rutinoside was one-third of that from onions. Absorption kinetics and bioavailibility might be determined by the type of glycoside. Dietary Quercetin could increase the antioxidant capacity of blood plasma.

  • Relative bioavailability of the antioxidant flavonoid Quercetin from various foods in man
    FEBS Letters, 1997
    Co-Authors: Peter C H Hollman, John M.p. Van Trijp, Michel N.c.p. Buysman, Martijn S. Martijn, Marcel J.b. Mengelers, Jeanne H M De Vries, Martijn B. Katan
    Abstract:

    Quercetin is a strong antioxidant and a major dietary flavonoid, Epidemiological studies suggest that consumption of Quercetin protects against cardiovascular disease, but its absorption in man is controversial. We fed nine subjects a single large dose of onions, which contain glucose conjugates of Quercetin, apples, which contain both glucose and non-glucose Quercetin glycosides, or pure Quercetin-3-rutinoside, the major Quercetin glycoside in tea. Plasma levels were then measured over 36 h. Bioavailability of Quercetin from apples and of pure Quercetin rutinoside was both 30% relative to onions. Peak levels were achieved less than 0.7 h after ingestion of onions, 2.5 h after apples and 9 h after the rutinoside. Half-lives of elimination were 28 h for onions and 23 h for apples. We conclude that conjugation with glucose enhances absorption from the small gut. Because of the long half-lives of elimination, repeated consumption of Quercetin-containing foods will cause accumulation of Quercetin in blood.

  • absorption and disposition kinetics of the dietary antioxidant Quercetin in man
    Free Radical Biology and Medicine, 1996
    Co-Authors: Peter C H Hollman, John M.p. Van Trijp, Marcel J.b. Mengelers, Jeanne H M De Vries, Martijn V D Gaag, Martijn B. Katan
    Abstract:

    Quercetin is a dietary antioxidant that prevents oxidation of low-density lipoproteins in vitro by scavenging of free oxygen radicals. Its intake was inversely associated with coronary heart disease mortality in Dutch elderly men. However, data on absorption of Quercetin in man are scarce and contradictory. We studied the time course of the plasma Quercetin concentration in two subjects after ingestion of fried onions containing Quercetin glucosides equivalent to 64 mg of Quercetin aglycone. Peak plasma levels of 196 ng/ml were reached after 2.9 h, with a half-life of absorption of 0.87 h. The half-life of the distribution phase was 3.8 h, and of the subsequent elimination phase 16.8 h. After 48 h the plasma concentration was about 10 ng/ml. We conclude that Quercetin glucosides from onions are absorbed and are eliminated slowly throughout the day. Thus, the dietary antioxidant Quercetine could increase the antioxidant capacity of blood plasma.

  • Absorption of dietary Quercetin glycosides and Quercetin in healthy ileostomy volunteers
    American Journal of Clinical Nutrition, 1995
    Co-Authors: Peter C H Hollman, Sonja D. Van Leeuwen, Marcel J.b. Mengelers, Jeanne H M De Vries, Martijn B. Katan
    Abstract:

    Quercetin is a dietary antioxidant that prevents oxidation of low-density lipoproteins in vitro. Intake of Quercetin was inversely associated with coronary heart disease mortality in elderly Dutch men. However, the extent of absorption of Quercetin in humans is unclear. The aim of this study was to quantify absorption of various forms of Quercetin. Nine healthy ileostomy subjects were studied, to avoid losses caused by colonic bacteria. They followed a Quercetin-free diet for 12 d; on days 4, 8, and 12 they received a supplement of fried onions at breakfast (rich in Quercetin glucosides) equivalent to 89 mg aglycone, pure Quercetin rutinoside (the major Quercetin compound in tea) equivalent to 100 mg aglycone, or 100 mg pure Quercetin aglycone, in random order. Subsequently, participants collected ileostomy effluent and urine for 13 h. In vitro incubations of Quercetin or its glycosides with gastrointestinal fluids showed minimal degradation. Absorption of Quercetin, defined as oral intake minus ileostomy excretion and corrected for 14% degradation within the ileostomy bag, was 52 +/- 15% for Quercetin glucosides from onions, 17 +/- 15% for Quercetin rutinoside, and 24 +/- 9% for Quercetin aglycone. Mean excretion of Quercetin or its conjugates in urine was 0.5% of the amount absorbed; Quercetin excretion in urine was negatively correlated with excretion in ileostomy effluent (r = -0.78, n = 27). We conclude that humans absorb appreciable amounts of Quercetin and that absorption is enhanced by conjugation with glucose.

Juong G Rhee - One of the best experts on this subject based on the ideXlab platform.

  • effects of low dose Quercetin cancer cell specific inhibition of cell cycle progression
    Journal of Cellular Biochemistry, 2009
    Co-Authors: Jaehoon Jeong, Jee Young An, Yong Tae Kwon, Juong G Rhee
    Abstract:

    Quercetin is a flavonoid present in many vegetables, fruits, and beverages. Due to its anti-oxidant, anti-tumor, and anti-inflammatory activity, Quercetin has been studied extensively as a chemoprevention agent in several cancer models. Since most of these studies used higher doses of Quercetin than clinically achievable, we focused on the effectiveness of physiologically relevant doses of Quercetin. A low dose of Quercetin exerted cancer cell-specific inhibition of proliferation and this inhibition resulted from cell cycle arrest at the G1 phase. Quercetin induced p21 CDK inhibitor with a concomitant decrease of phosphorylation of pRb, which inhibits the G1/S cell cycle progression by trapping E2F1. A low dose of Quercetin induced mild DNA damage and Chk2 activation, which is the main regulator of p21 expression by Quercetin. In addition, Quercetin down-regulated the cyclin B1 and CDK1, essential components of G2/M cell cycle progression. Inhibition of the recruitment of key transcription factor NF-Y to cyclin B1 gene promoter by Quercetin led to transcriptional inhibition. This study proved that the chemo-preventive efficacy of a physiologically relevant dose of Quercetin can be achievable through the inhibition of cell cycle progression. J. Cell. Biochem. 106: 73–82, 2009. © 2008 Wiley-Liss, Inc.

  • effects of low dose Quercetin cancer cell specific inhibition of cell cycle progression
    Journal of Cellular Biochemistry, 2009
    Co-Authors: Jaehoon Jeong, Jee Young An, Yong Tae Kwon, Juong G Rhee
    Abstract:

    Quercetin is a flavonoid present in many vegetables, fruits, and beverages. Due to its anti-oxidant, anti-tumor, and anti-inflammatory activity, Quercetin has been studied extensively as a chemoprevention agent in several cancer models. Since most of these studies used higher doses of Quercetin than clinically achievable, we focused on the effectiveness of physiologically relevant doses of Quercetin. A low dose of Quercetin exerted cancer cell-specific inhibition of proliferation and this inhibition resulted from cell cycle arrest at the G1 phase. Quercetin induced p21 CDK inhibitor with a concomitant decrease of phosphorylation of pRb, which inhibits the G1/S cell cycle progression by trapping E2F1. A low dose of Quercetin induced mild DNA damage and Chk2 activation, which is the main regulator of p21 expression by Quercetin. In addition, Quercetin down-regulated the cyclin B1 and CDK1, essential components of G2/M cell cycle progression. Inhibition of the recruitment of key transcription factor NF-Y to cyclin B1 gene promoter by Quercetin led to transcriptional inhibition. This study proved that the chemo-preventive efficacy of a physiologically relevant dose of Quercetin can be achievable through the inhibition of cell cycle progression. J. Cell. Biochem. 106: 73–82, 2009. © 2008 Wiley-Liss, Inc.

Su Zeng - One of the best experts on this subject based on the ideXlab platform.

  • structure metabolism relationships for the glucuronidation of flavonoids by ugt1a3 and ugt1a9
    Journal of Pharmacy and Pharmacology, 2011
    Co-Authors: Yakun Chen, Shuqing Chen, Su Zeng
    Abstract:

    Objectives This study tries to find structure-metabolism relationships between flavonoids and human UGT1A3 and UGT1A9. Methods The glucuronidation of flavonoids was studied with recombinant UGT1A3 and UGT1A9, and the glucuronidation activity was determined by HPLC. Key findings Of the flavonoids studied, it was shown for the first time that baicalein, Quercetin-3-OCH 2 OCH 3 , Quercetin-4'-CH 3 , Quercetin-3'-OCH 3 and Quercetin-3'-Br are substrates of UGT1A3. Wogonin, baicalein, Quercetin-4'-Cl, Quercetin-3-OCH 2 OCH 3 , Quercetin-3-O-arabinoside, Quercetin-4'-CH 3 , Quercetin-3'-OCH 3 and Quercetin-3'-Br are the newly reported substrates of UGT1A9. The preferred substrates for UGT1A3 and UGT1A9 contain the hydroxyl group at the C7-position. The glycon and the position of the B ring have conspicuous influences on the glucuronidation activity, and other chemical structures of flavonoids have minor effects. Conclusions From the quantitative study, UGT1A9 in general has higher glucuronidation efficiency than UGT1A3.

  • Structure–metabolism relationships for the glucuronidation of flavonoids by UGT1A3 and UGT1A9
    Journal of Pharmacy and Pharmacology, 2010
    Co-Authors: Yakun Chen, Shuqing Chen, Su Zeng
    Abstract:

    Objectives This study tries to find structure-metabolism relationships between flavonoids and human UGT1A3 and UGT1A9. Methods The glucuronidation of flavonoids was studied with recombinant UGT1A3 and UGT1A9, and the glucuronidation activity was determined by HPLC. Key findings Of the flavonoids studied, it was shown for the first time that baicalein, Quercetin-3-OCH 2 OCH 3 , Quercetin-4'-CH 3 , Quercetin-3'-OCH 3 and Quercetin-3'-Br are substrates of UGT1A3. Wogonin, baicalein, Quercetin-4'-Cl, Quercetin-3-OCH 2 OCH 3 , Quercetin-3-O-arabinoside, Quercetin-4'-CH 3 , Quercetin-3'-OCH 3 and Quercetin-3'-Br are the newly reported substrates of UGT1A9. The preferred substrates for UGT1A3 and UGT1A9 contain the hydroxyl group at the C7-position. The glycon and the position of the B ring have conspicuous influences on the glucuronidation activity, and other chemical structures of flavonoids have minor effects. Conclusions From the quantitative study, UGT1A9 in general has higher glucuronidation efficiency than UGT1A3.

Rui Hai Liu - One of the best experts on this subject based on the ideXlab platform.

  • In vitro digestion and lactase treatment influence uptake of Quercetin and Quercetin glucoside by the Caco-2 cell monolayer.
    Nutrition Journal, 2005
    Co-Authors: Jeanelle Boyer, Dan L. Brown, Rui Hai Liu
    Abstract:

    Quercetin and Quercetin glycosides are widely consumed flavonoids found in many fruits and vegetables. These compounds have a wide range of potential health benefits, and understanding the bioavailability of flavonoids from foods is becoming increasingly important. This study combined an in vitro digestion, a lactase treatment and the Caco-2 cell model to examine Quercetin and Quercetin glucoside uptake from shallot and apple homogenates. The in vitro digestion alone significantly decreased Quercetin aglycone recovery from the shallot digestate (p 0.05). Digestion increased the Caco-2 cell uptake of shallot Quercetin-4'-glucoside by 2-fold when compared to the non-digested shallot. Despite the loss of Quercetin from the digested shallot, the bioavailability of Quercetin aglycone to the Caco-2 cells was the same in both the digested and non-digested shallot. Treatment with lactase increased Quercetin recovery from the shallot digestate nearly 10-fold and decreased Quercetin-4'-glucoside recovery by more than 100-fold (p < 0.05), but had no effect on Quercetin recovery from apple digestates. Lactase treatment also increased shallot Quercetin bioavailability to the Caco-2 cells approximately 14-fold, and decreased shallot Quercetin-4'-glucoside bioavailability 23-fold (p < 0.05). These Caco-2 cells had lactase activity similar to that expressed by a lactose intolerant human. The increase in Quercetin uptake following treatment with lactase suggests that dietary supplementation with lactase may increase Quercetin bioavailability in lactose intolerant humans. Combining the digestion, the lactase treatment and the Caco-2 cell culture model may provide a reliable in vitro model for examining flavonoid glucoside bioavailability from foods.

  • In vitro digestion and lactase treatment influence uptake of Quercetin and Quercetin glucoside by the Caco-2 cell monolayer
    Nutrition Journal, 2005
    Co-Authors: Jeanelle Boyer, Dan Brown, Rui Hai Liu
    Abstract:

    BACKGROUND: Quercetin and Quercetin glycosides are widely consumed flavonoids found in many fruits and vegetables. These compounds have a wide range of potential health benefits, and understanding the bioavailability of flavonoids from foods is becoming increasingly important. METHODS: This study combined an in vitro digestion, a lactase treatment and the Caco-2 cell model to examine Quercetin and Quercetin glucoside uptake from shallot and apple homogenates. RESULTS: The in vitro digestion alone significantly decreased Quercetin aglycone recovery from the shallot digestate (p < 0.05), but had no significant effect on Quercetin-3-glucoside recovery (p > 0.05). Digestion increased the Caco-2 cell uptake of shallot Quercetin-4'-glucoside by 2-fold when compared to the non-digested shallot. Despite the loss of Quercetin from the digested shallot, the bioavailability of Quercetin aglycone to the Caco-2 cells was the same in both the digested and non-digested shallot. Treatment with lactase increased Quercetin recovery from the shallot digestate nearly 10-fold and decreased Quercetin-4'-glucoside recovery by more than 100-fold (p < 0.05), but had no effect on Quercetin recovery from apple digestates. Lactase treatment also increased shallot Quercetin bioavailability to the Caco-2 cells approximately 14-fold, and decreased shallot Quercetin-4'-glucoside bioavailability 23-fold (p < 0.05). These Caco-2 cells had lactase activity similar to that expressed by a lactose intolerant human. CONCLUSIONS: The increase in Quercetin uptake following treatment with lactase suggests that dietary supplementation with lactase may increase Quercetin bioavailability in lactose intolerant humans. Combining the digestion, the lactase treatment and the Caco-2 cell culture model may provide a reliable in vitro model for examining flavonoid glucoside bioavailability from foods.