Influence of fatty acid patterns on the intestinal absorption pathway of quercetin in thoracic lymph duct-cannulated rats.

Since it is known that dietary fats improve the bioavailability of the flavonol quercetin, we purposed to investigate whether this effect is due to increased lymphatic transport of quercetin. In rats with implanted catheters in the thoracic lymph duct, we administered quercetin into the duodenum with TAG emulsions containing either long-chain fatty acids (LCT) or medium-chain fatty acids (MCT). Controls received quercetin together with a glucose solution.

Chronic quercetin feeding decreases plasma concentrations of salicylamide phase II metabolites in pigs following oral administration.

We investigated acute effects and effects after chronic intake of the orally administered flavonol quercetin on pharmacokinetics of salicylamide metabolites (SAM) after oral administration of salicylamide in pigs. Salicylamide (8 mg/kg body weight) was orally administered to seven pigs either without or with quercetin (10 mg/kg body weight). Additionally, salicylamide was administered to five pigs that had received a diet supplemented with the flavonol for 1 week.

Oral bioavailability of quercetin from different quercetin glycosides in dogs.

Although the flavonol quercetin is used as a supplement in commercial dog food, data on quercetin bioavailability in dogs are not available. Thus, we investigated quercetin bioavailability (measured as area under the concentration-time curve) in nine adult beagle dogs at an oral dose of 10 mg/kg body weight (b.w.

Gene Regulatory Effects of Ginkgo biloba Extract and Its Flavonol and Terpenelactone Fractions in Mouse Brain.

The standardised Ginkgo biloba extract EGb761 is known for its potential beneficial effects in the prevention and therapy of neurodegenerative disorders including Alzheimer's disease (AD). However, the molecular mechanisms and the specific role of its constituents are largely unknown. The aim of the present feeding trial was to investigate the effects of EGb761 and its major constituents on the expression of genes encoding for proteins involved in the pathogenesis of AD in mouse brain.

Effects of the flavonol quercetin on the bioavailability of simvastatin in pigs.

The influence of the dietary flavonol quercetin on the pharmacokinetics of the HMG-CoA reductase inhibitor simvastatin was investigated in pigs. Simvastatin (0.25mg/kg body weight) was orally administered to six pigs either without or with quercetin (10mg/kg).

The influence of postharvest processing and storage of foodstuffs on the bioavailability of flavonoids and phenolic acids.

Postharvest processing and storage not only influence the content and composition of flavonoids and phenolic acids in foodstuffs, thereby altering the amount of potentially bioavailable bioactive compounds, but can also modify their chemical form. Moreover, due to the intensive metabolism during absorption, the metabolites circulating in blood differ from the parent compounds found in food. Thus, it is difficult to predict potential in vivo effects of phenolic compounds merely by their contents in foodstuffs.

Effect of a short- and long-term treatment with Ginkgo biloba extract on amyloid precursor protein levels in a transgenic mouse model relevant to Alzheimer's disease.

Several clinical trials have reported beneficial effects of the Ginkgo biloba extract EGb761 in the prevention and therapy of cognitive disorders including Alzheimer's disease (AD). The aim of the present long-term feeding trial was to study the impact of dietary EGb761 on Amyloid precursor protein (APP) metabolism in mice transgenic for human APP (Tg2576). Tg2576 mice were fed diets with and without EGb761 (300 mg/kg diet) for 1 and 16 months, respectively.

Tissue distribution of quercetin in pigs after long-term dietary supplementation.

Although the flavonol quercetin is intensively investigated, our knowledge about its bioavailability and possible target organs is far from being complete. The aim of this study was to check the potential of quercetin to accumulate in various tissues after long-term dietary treatment compared with a single treatment with flavonol. Pigs ingested either a single dose of quercetin aglycone (25 mg/kg body weight; Expt.

Effect of dietary flavonoids on pathways involved in drug metabolism.

Flavonoids are a large group of plant polyphenols with presumed beneficial effects on several common diseases. The use of dietary supplements enriched with flavonoids is becoming increasingly popular. These polyphenols are substrates of enzymes like cytochrome P450 monooxygenases and phase II conjugation enzymes, as well as of drug transporters involved in drug excretion.

Ginkgo biloba extract and its flavonol and terpenelactone fractions do not affect beta-secretase mRNA and enzyme activity levels in cultured neurons and in mice.

Numerous clinical trials have reported beneficial effects of the Ginkgo biloba extract EGb761 in the prevention and therapy of cognitive disorders including Alzheimer's disease (AD). Although neuroprotective properties of EGb761 have been consistently reported, the molecular mechanisms of EGb761 and the specific role of its major constituents, the flavonols and terpenlactones, are largely unknown. One major hallmark of AD is the deposition of amyloid-beta (A beta) as amyloid plaques in the brain.

The fatty acid pattern of dietary fat influences the oral bioavailability of the flavonol quercetin in pigs.

We have shown recently that dietary fat content influences the bioavailability of the flavonol quercetin. In the present study, the influence of the fatty acid pattern of dietary fats on the oral bioavailability of quercetin was investigated. Quercetin (30 micromol/kg body weight) was administered to growing pigs (n 6) in test meals consisting either of 200 g of a standard pig diet (2% crude fat) or of the same diet supplemented with 15 g fat/100 g diet using either medium-chain (MCT) or long-chain fatty acid triacylglycerols (LCT).

The potential of flavonoids to influence drug metabolism and pharmacokinetics by local gastrointestinal mechanisms.

In recent years, public and scientific interest in plant flavonoids has tremendously increased due to postulated health benefits. Whereas the amount of flavonoids ingested with the regular diet is rather low, the use of supplements enriched with these polyphenolics is becoming increasingly popular. This raises concerns about possible interactions of flavonoids with therapeutic drugs, because both are xenobiotics and, thus, share at least partially the same metabolic pathways.

In vitro degradation of the flavonol quercetin and of quercetin glycosides in the porcine hindgut.

The present study investigated the microbial degradation of the plant flavonol quercetin and its naturally occurring glycosides isoquercitrin and rutin in the porcine hindgut. The experiments were carried out with the semicontinuous colon-simulation technique. The fluid and particle phase of pig hindgut contents from freshly slaughtered animals were used for the in vitro incubations.

Effect of the flavonol quercetin on membrane conductances in rat colonic crypt cells.

The plant polyphenol quercetin was shown to induce Cl- secretion in rat colon. This study was performed to investigate the alterations of membrane conductances in isolated epithelial cells induced by quercetin. Whole-cell patch-clamp recordings were performed in isolated crypts from rat distal colon.

Quercetin glucosides inhibit glucose uptake into brush-border-membrane vesicles of porcine jejunum.

Recent experimental data point to an interaction of dietary flavonol monoglucosides with the intestinal Na-dependent glucose transporter 1 (SGLT1). To investigate this interaction in more detail, we performed experiments with SGLT1-containing brush-border-membrane vesicles (BBMV) from pig jejunum. The flavonol quercetin-3-O-glucoside (Q3G) concentration-dependently inhibited Na-dependent uptake of radioactively labelled d-glucose into BBMV.

Bioavailability of quercetin in pigs is influenced by the dietary fat content.

The flavonol quercetin is one of the most prevalent flavonoids found in edible plants. In this study, the influence of dietary fat on oral bioavailability of quercetin was investigated. Quercetin (30 micromol/kg body weight) was administered either as the lipophilic aglycone or as the more hydrophilic quercetin-3-O-glucoside in test meals differing in fat content (3, 17, or 32 g fat/100 g diet) to growing pigs.

The bioavailability of quercetin in pigs depends on the glycoside moiety and on dietary factors.

Recent investigations suggest that the bioavailability of quercetin depends on the glycoside moiety of the quercetin glycosides present in the diet. In this study, we compared the oral bioavailability of quercetin from quercetin aglycone and two different quercetin glycosides in pigs. Pigs were equipped with permanent catheters in the jugular and portal veins.

Gossypol induces chloride secretion in rat proximal colon.

The effect of gossypol on electrolyte transport was investigated in rat colon mounted in Ussing chambers. The addition of gossypol to the mucosal or serosal side led to an increase in mucus secretion, which we did not quantify. Mucosally or serosally added gossypol also induced a rise in short circuit current (I(sc)) and tissue conductance (G(t)).

The flavonol quercetin activates basolateral K(+) channels in rat distal colon epithelium.

1. The flavonol quercetin has been shown to activate a Cl(-) secretion in rat colon. Unlike the secretory activity of the related isoflavone genistein, quercetin's secretory activity does not depend on cyclic AMP; instead, it depends on Ca(2+).