Pharmacokinetics and bioavailability of the flavonol quercetin in humans

Article (PDF Available)inInternational journal of clinical pharmacology and therapeutics 37(5):219-33 · June 1999with532 Reads
Source: PubMed
Flavonoids are plant polyphenolic compounds present in the daily diet. Latest epidemiological studies point to a crucial role of the flavonol quercetin in the prevention of cardiovascular diseases. It is assumed that this protective effect derives from the antioxidative capacity which quercetin shows in in vitro experiments. The antiproliferative and antimutagenic activities in vitro have made it a candidate for clinical trials in cancer therapy. Quercetin is also regarded as a putative active compound in various phytopharmaceuticals. However, in vivo data on the disposition, absorption, bioavailability, and metabolism of quercetin after intravenous and oral administration in humans are scarce and contradictory. The pharmacokinetic parameters following intravenous injection were determined in two studies. The elimination half-life was reported to be 2.4 h and 0.7 h, the volume of distribution at steady-state was 92.6 l and 6.2 l, and total body clearance was 34.6 lxh(-1) and 28.1 lxh(-1), respectively. Absorption after oral administration ranged from 0 to over 50% of the dose. These inconsistencies can partly be attributed to a lack of highly sensitive and specific assay methodology. The data available so far are insufficient to clarify whether or not quercetin can be held responsible for any protective or curative effect observed after oral intake.

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    • "The limited research suggests that quercetin and its metabolites tend to accumulate in the organs involved in its metabolism and excretion, and that perhaps mitochondria might be an area of quercetin concentration within cells36373839404142. Kidney is a major organ of excretion. Quercetin concentration in urine increased with the increasing dose and time after intake of fruit juice was ingested in human [36], perhaps benzoic acid derivatives are common metabolite of quercetin [37]. Human subjects can absorb significant amounts of quercetin from food or supplements, and elimination is quite slow, with a reported half-life ranging from 11 to 28 h [38]. "
    [Show abstract] [Hide abstract] ABSTRACT: In vitro and some animal models have shown that quercetin, a polyphenol derived from plants, has a wide range of biological actions including anti-carcinogenic, anti-inflammatory and antiviral activities; as well as attenuating lipid peroxidation, platelet aggregation and capillary permeability. This review focuses on the physicochemical properties, dietary sources, absorption, bioavailability and metabolism of quercetin, especially main effects of quercetin on inflammation and immune function. According to the results obtained both in vitro and in vivo, good perspectives have been opened for quercetin. Nevertheless, further studies are needed to better characterize the mechanisms of action underlying the beneficial effects of quercetin on inflammation and immunity.
    Full-text · Article · Mar 2016
    • "Nevertheless, they are also rapidly metabolized and no parent glycosides have been detected in plasma [16]. Quercetin yields various metabolites with retained flavonoid structure, among others, glucuronides, sulphates, diglucuronide, glucuronidesulphate of quercetin or its methylated metabolites isorhamnetin and tamarixetin [17,18]. In the latter two cases, only low concentrations of nonconjugated isorhamnetin and tamarixetin are found in plasma [14, 15]. "
    [Show abstract] [Hide abstract] ABSTRACT: Scope: A number of studies have suggested that higher flavonoid intake is associated with lower cardiovascular mortality. The direct vasodilatory potential of flavonoids is one proposed mechanism for this link. However, the bioavailability of flavonoid aglycones is low. The metabolites of flavonoids could therefore explain/contribute to the effect. Methods and results: We tested a series of quercetin metabolites formed by both human enzymes and colon microflora. In vitro, a number of these metabolites resulted in vasodilation of isolated rat aortic rings, precontracted with norepinephrine. However, 3-(3-hydroxyphenyl)propionic acid /3HPPA/ was clearly the most potent with an effect of about one order better than quercetin or its close methylderivatives, isorhamnetin and tamarixetin. In contrast, quercetin-3-O-glucuronide was void of any effect. The vasodilatory activity of 3HPPA was confirmed by in vivo experiments on both normotensive and spontaneously hypertensive rats. Subsequent experiments showed that the arterial blood pressure decrease found after 3HPPA was associated with the peripheral action of the compound on vascular beds and was NO-based. Conclusion: This is the first study showing that a metabolite of flavonoids formed by human microflora has haemodynamic effects. This article is protected by copyright. All rights reserved.
    Article · Jan 2016
    • "It has been well established that flavonoids in nature are the potential antioxidants. Quercetinm, a flavonoid that exists in numerous plants, possesses a very good antioxidant activity and hence it is currently being used in health food stores [24]. Another class of natural products, viz. "
    [Show abstract] [Hide abstract] ABSTRACT: The present work involves extraction of phytochemicals from the root bark of a well-known Indian traditional medicinal plant, viz. Mammea suriga, with various solvents and evaluation of their in vitro antimicrobial and antioxidant activities using standard methods. The phytochemical analysis indicates the presence of some interesting secondary metabolites like flavonoids, cardiac glycosides, alkaloids, saponins and tannins in the extracts. Also, the solvent extracts displayed promising antimicrobial activity against Staphylococcus aureus, Bacillus subtilis and Cryptococcus neoformans with zone of inhibition with a range of 20–33 mm. Further, results of their antioxidant screening revealed that aqueous extract (with IC50 values of 111.51±1.03 and 31.05±0.92 μg/mL in total reducing power assay and DPHH radical scavenging assay, respectively) and ethanolic extract (with IC50 values of 128.00±1.01 and 33.25±0.89 μg/mL in total reducing power assay and DPHH radical scavenging assay, respectively) were better antioxidants than standard ascorbic acid. Interestingly, FT-IR analysis of each extract established the presence of various biologically active functional groups in it.
    Article · Jan 2015
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