Quercetin

Looking to buy Quercetin? Buy from Amazon.com

Quercetin is a Bioflavonoids found in fruits and vegetables, but highest levels are found in apples and onions.

Like many other bioflavonoids, Quercetin has anti-oxidant, anti-artherogenic, and anti-carcinogenic properties. Quercetin is also neuroactive, with some of the same abilities as Caffeine but less potent.

There is a divide between the effects seen in quercetin in in vitro (cell cultured) studies and in vivo (in living) studies, with cell studies showing great results that are not that amazing in humans or animals. This is mostly due to quercetin having low oral bioavailability (low percentage of the compound is absorbed and put to use), but could also be due to in vitro studies using a form of quercetin called 'quercetin aglycone' whereas this particular form is never found in the blood, even after ingested, as it it gets changed in the liver.

Many studies also note a high range of differences between people who ingest the same amount of quercetin, suggesting a large degree of variability is possible with supplementation.

Quercetin has GRAS (Generally Recognized As Safe) status, and no side-effects have yet been noted in doses of a few grams a day in either humans or animals.

Looking to buy Quercetin? Buy from Amazon.com

Follow this Page for updates

Dosages of quercetin used are in the range of 12.5 to 25mg per kg body weight, which translates to a range of 1,136-2,272mg daily consumption of quercetin when in isolation.

It is suggested to supplement with other Bioflavonoids such as Resveratrol, genistein, or Green Tea Catechins to increase the potency synergistically and theoretically get the benefits at a reduced level of intake.

When looking for quercetin, the form of dihydrate has the apparent best bioavailability followed by glycosides, aglycone, and finally rutinoside.

The Human Effect Matrix looks at human studies (excluding animal/petri-dish studies) to tell you what effect Quercetin has in your body, and how strong these effects are.

Level of Evidence	Effect	Change	Magnitude of Effect Size	Scientific Consensus	Comments
C	Sleep Quality			100% See study	No significant influence on sleep quality
C	Fatigue			100% See study	No significant influence on fatigue nor vitality in otherwise healthy persons
C	Anaerobic Running Capacity			100% See study	No significant influence on anaerobic exercise capacity when preloaded
C	Inflammation			50% See 2 studies	Mixed influence on inflammation, but does not appear to at all be practically significant
C	Intestinal Permeability		Minor	100% See study	An increase in the amount of intestinal permeability induced by training in the heat has been noted with quercetin supplementation, which is an adverse event; the influence... show of quercetin at rest is uncertain
C	Exercise-induced Stress Response		Notable	100% See study	The exercise-induced increase in HSP70 expression is abolished with quercetin preloading
C	General Oxidation		Minor	100% See study	May reduce oxidative biomarkers in serum
C	Blood Pressure			100% See study	No acute alterations in blood pressure following Quercetin supplementation
C	Metabolic Rate			100% See study	No significant influence on metabolic rate following acute Quercetin supplementation
C	Fat Oxidation			100% See study	No significant alterations in fat oxidation noted with quercetin supplementation
D	Total Cholesterol		Minor	100% See study	An increase in total cholesterol has been noted, but mostly attributed to HDL
D	LDL-C		Minor	100% See study	A decrease in LDL-C has been noted in persons with high blood lipids
D	HDL-C		Minor	100% See study	An increase in HDL-C has been noted following quercetin supplementation

Looking to buy Quercetin? Buy from Amazon.com or BodyBuilding.com

Edit1. Sources and Structure

1.1. Food Sources

Quercetin is one of the most prominent bioflavonoid compounds in plants, and is found in the food products:

• Onions, commonly seen as the best source of Quercetin^[1] at 60-100mg/100g fresh weight^[2]
• Grapes,^[3] and due to that Wine also has a Quercetin content

Dietary supplements (fruits, leaves, or herbal compounds) may also confer a Quercetin content either as free Quercetin or one of its glycosides; popular or particularly good sources of Quercetin include:

• Herbs that are generally rich in all polyphenolics, such as Euonymus alatus (115mg/100g Quercetin in ethanolic extract),^[4][5] Nelumbo Nucifera (where Quercetin consists of 25-30% of the total flavonoids in flowers and 67.25-90.66% in the leaves and seeds)^[6]
• Ginkgo Biloba^[7]
• Morus Alba (Moraceae)

1.2. Structure

Quercetin possesses the basic flavonol backbone (hydroxylation on the 3 carbon of the central ring) with two other hydroxylations on the outer ring. Removal of one of these hydroxy groups creates Kaempferol, which is the backbone for the active metabolite of Horny Goat Weed, Icariin. Substitution of the removed group with a methoxy group creates the metabolite isorhamnetin. A glycoside of quercetin, called quercetin 3-O-beta-rutinode, is more commonly referred to as rutin.^[8]

Edit2. Pharmacology

2.1. Absorption and the Intestines

After oral ingestion of quercetin, it is taken up from the gut into the liver. The conjugate of quercetin influences its absorption rates. At least intestinally, quercetin glycosides (food source) were found to have a 52+/-15% uptake, quercetin rutinoside (tea) has a 17+/-15% uptake, and supplemental quercetin aglycone had a 24+/-9% uptake.^[9]

One pharmacokinetic study in humans following consumption of 500mg Quercetin (as aglycone) noted that the delivery of Quercetin chews had a C_max of 1051.9+/-393.1ug/mL at T_max of 3.66 hours, with the C_max and T_max of Food bar format and juice suspension reaching 698.1+/-189.5μg/L (in 2.3h) and 354.4+/-87.6μg/L (4.7h), respectively.^[10] This study had all forms using QU995, and was unable to conclude any significant differences between groups due to higher variability (just different average).^[10]

Appears to per se have a moderate to low bioavailability, depending on the source

Due to enhanced lymphatic release of Quercetin following administration of Long-Chain Fatty acids (LCFAs), it is thought that the formation of micelles from LCFAs can enhance the apparent bioavailability of Quercetin.^[11]

Quercetin is a potent inhibitor of intestinal sulfurotransferases, and has some activity on hepatic sulfurotransferases as well.^[12] This mechanism may increase bioavailability of compounds that undergo extensive intestinal metabolism via this method, like Resveratrol.^[13]

Interacts with intestinal conjugation enzymes, which may predispose Quercetin to nutrient-nutrient interactions

2.2. Hepatic (Liver)

After the liver, quercetin exists in the blood solely as quercetin glucuronides.^[14] Regardless of initial source, all forms of quercetin undergo hydrolysis and get glucuronidated in the liver before being released into systemic circulation.

2.3. Circulating Quercetin

Quercetin has been measured in the blood 15-30 minutes after ingestion of 250-500mg, with peak levels 120-180 minutes after ingestion and returns to baseline levels in humans 24 hours after ingestion. Additional ingestion of quercetin dose-dependently increases plasma quercetin glucoronides.^[15] Accumulation of quercetin has been noted in many tissues including kidneys, colon, liver, brain, lung and muscle.

Systemically, resting quercetin levels are highly variable. The previous study noted resting quercetin levels (from food intake) ranging from 30-163uM/L. After supplementation of 50,100,and 150mg quercetin dihydrate serum ranges increased to 95.9-255, 164-497, and 240-1292 respectively. These concentrations are much larger than neural concentrations.^[16]

However, those are general ideas as quercetin bioavailability seems contradictory in many studies, possibly due to large differences between individuals and quercetin supplementation^[17]

2.4. Neurology

In pigs, feeding of quercetin aglycone at 50mg/kg BW increased neurological concentrations to 0.02uM,^[18] while another study noted levels of 0.22uM with a dosage of 500mg/kg BW.^[19]

Quercetin is a highly polar (water-soluble) compound, but seems to be able to cross models of the blood brain barrier.^[20][21] Mixed onion flavanoids (of which Quercetin comprises a large amount) appear to have around a 60% efficacy in crossing the BBB.^[22]

Edit3. Notable Enzymatic/Receptor Interactions

Like some other Bioflavonoids, quercetin has the ability to inhibit the xanthine oxidase enzyme^[23]

Quercetin, like Caffeine, is also an adenosine receptor antagonist^[24] although at a dose equivalent to 200mg caffeine quercetin failed to have caffeine like effects.

Quercetin has its antioxidant potential reduced via the enzyme catechol-o-methyl transferase^[25] which is strongly inhibited by Green Tea Catechins.

Edit4. Neurology and the Brain

4.1. Neuroprotection

In vitro studies at 25-100uM show that quercetin is able to protect PC-12 neurons from oxidative stress induces from toxins and peroxides^[26][27] as well as inhibiting formation of beta-amyloid pigmentation.^[28] Protective effects against some ROS has been reported as low as 0.5uM of quercetin-3-glucuronide, which may be the only effects notable with basic quercetin supplementation due to low oral bioavailability and brain concentrations.^[29]

On the other side of things, quercetin can be a potential neurotoxic substance in supraphysiological levels. Quercetin has been noted in some studied to initially protect the neuron and later act as a toxin in in vitro studies.^[30] Quercetin seems to, in pure in vitro neuronal cultures, to induce toxicity at a concentration of 1-10uM^[31] but is protected to a degree in vivo by metabolization by glial cells around neurons.^[32] Inducing supraphysiological concentrations of quercetin in the range of 30uM-100uM in cultures with glia cells shows no signs of toxicity and increased survivial of neurons, however the effectiveness of the quercetin per unit is reduced by the protecting metabolization.^[33][34]

4.2. Inflammation

In regards to neuroinflammation, quercetin is able to act as an anti-inflammatory in the brain (and thus protectant of Alzheimers and Parkinsons, of which inflammation is an exacerbating factor) by increasing heme-oxygenase-1 expression which suppresses nitric oxide release induced from an inflammation response at concentrations as low as 10uM.^[35][36] Suppression of other pro-inflammatory markers, TNF-alpha and IL-1alpha, occurred with quercetin (and resveratrol) at concentrations as low as 0.1uM.^[37]

4.3. Stimulation

When fed to rats at doses between 10-40mg/kg bodyweight, Quercetin does not seem to influence movement or stimulation any more than control.^[38]

4.4. Learning

One animal model noted that Quercetin, dosed at 10,20, or 40mg/kg bodyweight taken orally, was able to reduce learning as assessed by the Y-Maze and Morris Water maze task^[38] yet no dose-dependence was noted. Only one other study has focused on cognition in healthy animals, and it was found that Quercetin was capable of deteriorating anterograde cognitive functions as assessed by the inhibitory avoidance task.^[39] The lowest dose used (10mg/kg), after body surface area conversions,^[40] correlated to 48.6mg Quercetin in an adult male human.

In these rats, lowered levels of phosphorylated CREB were noted.^[38] This protein (CREB) is activated when short-term memories are translated to long term memories via creating proteins^[41] and these proteins appear to be crucial to long-term memory storage.^[42][43] These may be downstream to a reduction in Akt phorphorylation also noted^[38] which appears to be a regulator of CREB.^[44] CREB phorphorylation was decreased by 28%, 37%, and 35% at 10,20,40mg/kg bodyweight and Akt by 29% (20mg/kg) and 53% (40mg/kg).^[38] The decreased phosphorylation of CREB paralleled that of CaMKII much more than it did Akt, and all results were recorded 1 hour after consumption.^[38] The authors hypothesized that Quercetin affects acquisitional memory.^[38]

Possible that Quercetin could adversely affect memory in healthy humans, but insufficient studies have been conducted

Edit5. Effects on Exercise Performance

Effects on exercise performance look promising on a molecular level, but studies done on an applicative level are mixed.

Quercetin has been found to increase cardiovascular performance in untrained men compared to a placebo dosed at 500mg twice a day^[45] and mice studies note positive effects on exercise performance and mitochondrial biogenesis at doses between 12.5 and 25mg/kg BW.^[46] Quercetin has also been noted to increase exercise output in trained cyclists at 300mg, but was studied in conjunction with Green Tea Catechins (300mg) and caffeine(45mg) along many vitamins.^[47]

In the above study, the catechins and anti-oxidants alone increased performance but the addition of quercetin added to said increase. This may be due to possible synergism between many Bioflavonoids compounds (of which Green Tea Catechins are a subset).

On the negative side of things, quercetin failed to increase performance in repeated sprint intervals when dosed at 1000mg/day (in 2 doses) of quercetin-3-glucoside^[23] and did not increase performance time trials on an erg bike at an acute dose of 2g^[48]

So although the effects of Quercetin on exercise performance look promising, there is not enough conclusive evidence to state whether supplementation will increase performance.

Edit6. Thermoregulation

6.1. Heat Shock Response

Quercetin appears to be an inhibitor of the Heat Shock Response, a response to heat exposure that results in activation of heat-shock and heat-response proteins^[49][50] that can have wide-reaching effects such increasing intestinal permeability.^[51] Specifically, Quercetin has shown inhibition at the level of phosporylation and trimerization in the cytosol^[52][53][54] and downstream effects on promoter binding^[55] and results of genetic signalling (mRNA expression and protein accumulation).^[50] Through these effects, it may mitigate the anti-inflammatory effects of Heat-Shock Protein 70 (HSP70).^[56] In humans, 30mg/kg quercetin a day (averaged to 2,000mg Quercetin daily) taken with exercise was shown to increase urinary lactulose on day 1, and increase both lactulose and serum endotoxin on day 7 after heat acclimatization should have occurred.^[52] These results suggest impairment of intestinal permability acutely, and prevention of beneficial adaptations to heat over continual heat exposure associated with 2g Quercetin supplementation.^[52]

Edit7. Interactions with Hormones

7.1. Testosterone

Quercetin, at 20mg/kg bodyweight, can prevent testicular damage from Dioxins and thus prevent a decline in testosterone levels;^[57] the mechanism seems to be through being an anti-oxidant present in the testes^[58] as it is the same mechanism by which quercetin protects the kidneys from Dioxins.^[59] Quercetin may also protect against physical injuries, as evidenced by rotating rat testicles 720 degrees clockwise.^[60]

Quercetin can increase aromatase activity 4x at a concentration of 100uM,^[61] but possesses inhibitory actions at a lower dosage (0.026uM).^[62] It shows some suppressive effects on mRNA transcription of aromatase in the corpus luteum^[63] and in a seemingly dose dependent manner, with 10uM being more potent than 100nM. Quercetin shows synergism with Apigenin in this regard.^[63] In intestinal cells, they do not influence mRNA levels but induce aromatase activity.^[64]

Using onion juice, a good source of Quercetin, testosterone levels can increase in rats after 4g/kg bodyweight daily for 20 days.^[65]

The biochemistry seems to be in line with an estrogen modulator; having the ability to regulate estrogen and androgen levels depending on its concentration.

Edit8. Quercetin Glycosides and Derivatives

A glycoside is a term used to refer to a molecule connected to sugar molecules. Glycosides tend to exist in plants as a storage form, and upon human consumption they can either be hydrolyzed into the molecule and sugars (two separate things to make note of) or remain bound together. For example, Cyanidin is a molecule while Cyanidin-3-O-Glucoside is a glycoside thereof that has some unique properties and can be detected in the blood after oral ingestion

Glycoside is a term that does not discriminate the sugar in concern, whereas the term glucoside may be used to refer to the same thing if the sugar is glucose; looking at the following list, Isoquercetin is both a glycoside (bound to sugar) and a glucoside (the sugar is glucose) but Rutin is only a glycoside and not a glucoside. The molecule with no sugars attached can be referred to an aglycone (without sugar) or aglucone (without glucose)

8.1. Quercetin-3-O-Rutinoside (Rutin)

Quercetin-3-O-Rutinoside is more commonly called Rutin, and consists of a Quercetin molecule bound to the sugar rutinose; rutinose is a disaccharide of rhamnose and glucose (6-O-L-rhamnosyl-D-glucose). It can be found in a variety of plants alongside Quercetin, but is in high amounts in Ziziphus Jujuba leaves.

8.2. Quercetin-3-O-Rhamnoside

Quercetin-3-O-Rhamnoside is a glycone where Quercetin is attached to the sugar Rhamnose, found in high levels in Irvingia Gabonensis

8.3. Quercetin-3-Glucoside (Isoquercetin)

Quercetin-3-Glucoside is a Quercetin molecule with a lone glucose sugar bound to the 3 carbon, and has the common name of Isoquercetin; it commonly co-exists with Quercetin in food products.

8.4. Quercetin 3-O-β-D-glucoside

Quercetin 3-O-β-D-glucoside is structurally similar to Isoquercetin, but with modifications on the glucose moiety.

8.5. Quercetin-4'-O-Glucoside (Spiraeoside)

Another glucoside of Quercetin, where the glucose is attached to the 4' carbon rather than the common 3 carbon; this conjugate is sometimes referred to as Spiraeoside, and is found in the herb Filipendula ulmaria as well as common onions.

8.6. Quercetin 3-D-galactoside (Hyperin)

Quercetin bound to a galactose molecule (one of the two constituents of lactose) results in a glycoside known as Hyperin, with other names included Hyperoside; this glycoside is in relatively high levels in the leaves of the plant bearing Chinese Hawthorn

8.7. Quercetin-3,6-Malonylglucoside

Quercetin-3,6-Malonylglucoside (Q3MG) is a monoglucoside structure with a malonyl attachment on the glucose moiety, found in high concentrations in the leaves of Morus Alba (260mg/100g^[66]) which exceeds that of onions, thought to be one of the best sources of Q3MG at 60-100mg/100g;^[2] Morus Alba leaf extracts (tea) is commonly consumed as an anti-diabetic therapy, although this may be more related to non-quercetin structures (the iminosugars, with 1-deoxynojirimycin being particularly important to Morus Alba).

8.8. Quercetin-3-O-robinobioside

Quercetin-3-O-robinobioside is a glycoside where Quercetin is attached to Robinose, Robinose being a rhamnose sugar attached to a galactose sugar and Robinoside being interchangeable with 6″-O-α-rhamnopyranosyl-β-galactopyranoside. This glycsoide is found in high levels in the leaves of Boerhaavia Diffusa.

8.9. Quercetin Rhamnohexoside

Quercetin Rhamnohexoside is a glycoside found in high levels in the leaves of Gynostemma Pentaphyllum, alongside Quercetin Dirhamnohexoside (an additional Rhamnose sugar).

The following molecules are variants on Quercetin, where the structure is slightly modified but not due to the addition of a sugar molecule to the structure

8.10. Methylated Quercetin Molecules

Pentamethylquercetin is a molecule where the Quercetin molecule has been methylated five additional times, and constitutes up to 0.391% of the dry weight of the leaves of Kaempferia Parviflora

3-O-Methylquercetin is a structure where the 3-carbon (where many glycosides attach) is methylated, and appears to be the main bioactive in Rhamnus Nakaharai

Edit9. Nutrient-Nutrient and Nutrient-Drug Interactions

9.1. Yerba Mate

Yerba Mate is a form of tea with a Caffeine content and a relatively unique blend of polyphenolic compounds. The saponin content of Yerba Mate synergistically works with Quercetin to suppress inflammation via NO and PGE(2).^[67]

The multiple faces of quercetin in neuroprotection

References

1. Yoo KS, Lee EJ, Patil BS. Quantification of quercetin glycosides in 6 onion cultivars and comparisons of hydrolysis-HPLC and spectrophotometric methods in measuring total quercetin concentrations. J Food Sci. (2010)
2. Arabbi PR, Genovese MI, Lajolo FM. Flavonoids in vegetable foods commonly consumed in Brazil and estimated ingestion by the Brazilian population. J Agric Food Chem. (2004)
3. Careri M, et al. Direct HPLC analysis of quercetin and trans-resveratrol in red wine, grape, and winemaking byproducts. J Agric Food Chem. (2003)
4. Zhang F, et al. Microwave-assisted extraction of rutin and quercetin from the stalks of Euonymus alatus (Thunb.) Sieb. Phytochem Anal. (2009)
5. Jeong EJ, et al. Inhibitory constituents of Euonymus alatus leaves and twigs on nitric oxide production in BV2 microglia cells. Food Chem Toxicol. (2011)
6. Goo HR, Choi JS, Na DH. Simultaneous determination of quercetin and its glycosides from the leaves of Nelumbo nucifera by reversed-phase high-performance liquid chromatography. Arch Pharm Res. (2009)
7. Wang FM, Yao TW, Zeng S. Determination of quercetin and kaempferol in human urine after orally administrated tablet of ginkgo biloba extract by HPLC. J Pharm Biomed Anal. (2003)
8. Murota K, et al. alpha-Oligoglucosylation of a sugar moiety enhances the bioavailability of quercetin glucosides in humans. Arch Biochem Biophys. (2010)
9. Absorption of dietary quercetin glycosides and quercetin in healthy ileostomy volunteers
10. Kaushik D, et al. Comparison of Quercetin Pharmacokinetics Following Oral Supplementation in Humans. J Food Sci. (2012)
11. Influence of fatty acid patterns on the intestinal absorption pathway of quercetin in thoracic lymph duct-cannulated rats
12. Pacifici GM. Inhibition of human liver and duodenum sulfotransferases by drugs and dietary chemicals: a review of the literature. Int J Clin Pharmacol Ther. (2004)
13. Harris RM, Waring RH. Sulfotransferase inhibition: potential impact of diet and environmental chemicals on steroid metabolism and drug detoxification. Curr Drug Metab. (2008)
14. Graefe EU, et al. Pharmacokinetics and bioavailability of quercetin glycosides in humans. J Clin Pharmacol. (2001)
15. Egert S, et al. Daily quercetin supplementation dose-dependently increases plasma quercetin concentrations in healthy humans. J Nutr. (2008)
16. Youdim KA, et al. Flavonoid permeability across an in situ model of the blood-brain barrier. Free Radic Biol Med. (2004)
17. Graefe EU, Derendorf H, Veit M. Pharmacokinetics and bioavailability of the flavonol quercetin in humans. Int J Clin Pharmacol Ther. (1999)
18. Tissue Distribution of Quercetin in Pigs after Long-Term Dietary Supplementation
19. de Boer VC, et al. Tissue distribution of quercetin in rats and pigs. J Nutr. (2005)
20. Faria A, et al. Flavonoid transport across RBE4 cells: A blood-brain barrier model. Cell Mol Biol Lett. (2010)
21. Ren SC, et al. {Quercetin permeability across blood-brain barrier and its effect on the viability of U251 cells}. Sichuan Da Xue Xue Bao Yi Xue Ban. (2010)
22. Dan H, Du WT, Fan XJ. {Study of flavanoids extracted from onion on the blood-brain barrier permeation and neuroprotective effects}. Zhongguo Zhong Xi Yi Jie He Za Zhi. (2011)
23. Abbey EL, Rankin JW. Effect of quercetin supplementation on repeated-sprint performance, xanthine oxidase activity, and inflammation. Int J Sport Nutr Exerc Metab. (2011)
24. Olson CA, et al. Effects of 2 adenosine antagonists, quercetin and caffeine, on vigilance and mood. J Clin Psychopharmacol. (2010)
25. Santos MR, et al. Influence of the metabolic profile on the in vivo antioxidant activity of quercetin under a low dosage oral regimen in rats. Br J Pharmacol. (2008)
26. Protective Effects of Quercetin and Vitamin C against Oxidative Stress-Induced Neurodegeneration
27. Sasaki N, et al. Protective effects of flavonoids on the cytotoxicity of linoleic acid hydroperoxide toward rat pheochromocytoma PC12 cells. Chem Biol Interact. (2003)
28. Kim H, et al. Effects of naturally occurring compounds on fibril formation and oxidative stress of beta-amyloid. J Agric Food Chem. (2005)
29. Shirai M, et al. Effect of a conjugated quercetin metabolite, quercetin 3-glucuronide, on lipid hydroperoxide-dependent formation of reactive oxygen species in differentiated PC-12 cells. Free Radic Res. (2006)
30. Time-dependent protective and harmful effects of quercetin on 6-OHDA-induced toxicity in neuronal SH-SY5Y cells
31. Jakubowicz-Gil J, et al. Cell death and neuronal arborization upon quercetin treatment in rat neurons. Acta Neurobiol Exp (Wars). (2008)
32. Glial metabolism of quercetin reduces its neurotoxic potential
33. Mercer LD, et al. Dietary polyphenols protect dopamine neurons from oxidative insults and apoptosis: investigations in primary rat mesencephalic cultures. Biochem Pharmacol. (2005)
34. Resveratrol protects dopaminergic neurons in midbrain slice culture from multiple insults
35. Chen JC, et al. Inhibition of iNOS gene expression by quercetin is mediated by the inhibition of IkappaB kinase, nuclear factor-kappa B and STAT1, and depends on heme oxygenase-1 induction in mouse BV-2 microglia. Eur J Pharmacol. (2005)
36. Kwon YS, et al. Modulation of suppressive activity of lipopolysaccharide-induced nitric oxide production by glycosidation of flavonoids. Arch Pharm Res. (2004)
37. Bureau G, Longpré F, Martinoli MG. Resveratrol and quercetin, two natural polyphenols, reduce apoptotic neuronal cell death induced by neuroinflammation. J Neurosci Res. (2008)
38. Jung WY, et al. Quercetin impairs learning and memory in normal mice via suppression of hippocampal phosphorylated cyclic AMP response element-binding protein expression. Toxicol Lett. (2010)
39. Salgueiro JB, et al. Anxiolytic natural and synthetic flavonoid ligands of the central benzodiazepine receptor have no effect on memory tasks in rats. Pharmacol Biochem Behav. (1997)
40. Reagan-Shaw S, Nihal M, Ahmad N. Dose translation from animal to human studies revisited. FASEB J. (2008)
41. Josselyn SA, Nguyen PV. CREB, synapses and memory disorders: past progress and future challenges. Curr Drug Targets CNS Neurol Disord. (2005)
42. Davis HP, Squire LR. Protein synthesis and memory: a review. Psychol Bull. (1984)
43. Costa-Mattioli M, et al. Translational control of long-lasting synaptic plasticity and memory. Neuron. (2009)
44. Du K, Montminy M. CREB is a regulatory target for the protein kinase Akt/PKB. J Biol Chem. (1998)
45. Davis JM, et al. The dietary flavonoid quercetin increases VO(2max) and endurance capacity. Int J Sport Nutr Exerc Metab. (2010)
46. Davis JM, et al. Quercetin increases brain and muscle mitochondrial biogenesis and exercise tolerance. Am J Physiol Regul Integr Comp Physiol. (2009)
47. Dietary anti-oxidant supplementation combined with Quercetin improves cycling time trial performance
48. Cheuvront SN, et al. No effect of nutritional adenosine receptor antagonists on exercise performance in the heat. Am J Physiol Regul Integr Comp Physiol. (2009)
49. Mizzen LA, Welch WJ. Characterization of the thermotolerant cell. I. Effects on protein synthesis activity and the regulation of heat-shock protein 70 expression. J Cell Biol. (1988)
50. Dokladny K, et al. Cellular and molecular mechanisms of heat stress-induced up-regulation of occludin protein expression: regulatory role of heat shock factor-1. Am J Pathol. (2008)
51. Dokladny K, Moseley PL, Ma TY. Physiologically relevant increase in temperature causes an increase in intestinal epithelial tight junction permeability. Am J Physiol Gastrointest Liver Physiol. (2006)
52. Kuennen M, et al. Thermotolerance and heat acclimation may share a common mechanism in humans. Am J Physiol Regul Integr Comp Physiol. (2011)
53. End DW, et al. Non-selective inhibition of mammalian protein kinases by flavinoids in vitro. Res Commun Chem Pathol Pharmacol. (1987)
54. Inhibition of heat shock factor activity prevents heat shock potentiation of glucocorticoid receptor-mediated gene expression
55. Hosokawa N, et al. Inhibition of the activation of heat shock factor in vivo and in vitro by flavonoids. Mol Cell Biol. (1992)
56. Liu WL, et al. Protective effects of heat shock protein70 induced by geranylgeranylacetone in atrophic gastritis in rats. Acta Pharmacol Sin. (2007)
57. Ciftci O, et al. Quercetin prevents 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced testicular damage in rats. Andrologia. (2011)
58. Ciftci O, Ozdemir I. Protective effects of quercetin and chrysin against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced oxidative stress, body wasting and altered cytokine productions in rats. Immunopharmacol Immunotoxicol. (2011)
59. Ciftci O, et al. Ameliorating effects of quercetin and chrysin on 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced nephrotoxicity in rats. Toxicol Ind Health. (2011)
60. Aktoz T, Kanter M, Aktas C. Protective effects of quercetin on testicular torsion/detorsion-induced ischaemia-reperfusion injury in rats. Andrologia. (2010)
61. Sanderson JT, et al. Induction and inhibition of aromatase (CYP19) activity by natural and synthetic flavonoid compounds in H295R human adrenocortical carcinoma cells. Toxicol Sci. (2004)
62. Zessner H, et al. Fractionation of polyphenol-enriched apple juice extracts to identify constituents with cancer chemopreventive potential. Mol Nutr Food Res. (2008)
63. Rice S, Mason HD, Whitehead SA. Phytoestrogens and their low dose combinations inhibit mRNA expression and activity of aromatase in human granulosa-luteal cells. J Steroid Biochem Mol Biol. (2006)
64. Sergent T, et al. CYP1A1 and CYP3A4 modulation by dietary flavonoids in human intestinal Caco-2 cells. Toxicol Lett. (2009)
65. Khaki A, et al. Evaluation of androgenic activity of allium cepa on spermatogenesis in the rat. Folia Morphol (Warsz). (2009)
66. Enkhmaa B, et al. Mulberry (Morus alba L.) leaves and their major flavonol quercetin 3-(6-malonylglucoside) attenuate atherosclerotic lesion development in LDL receptor-deficient mice. J Nutr. (2005)
67. Puangpraphant S, de Mejia EG. Saponins in yerba mate tea ( Ilex paraguariensis A. St.-Hil) and quercetin synergistically inhibit iNOS and COX-2 in lipopolysaccharide-induced macrophages through NFkappaB pathways. J Agric Food Chem. (2009)
68. Bigelman KA, et al. Effects of 6 weeks of quercetin supplementation on energy, fatigue, and sleep in ROTC cadets. Mil Med. (2011)
69. Konrad M, et al. The acute effect of ingesting a quercetin-based supplement on exercise-induced inflammation and immune changes in runners. Int J Sport Nutr Exerc Metab. (2011)
70. Talirevic E, Jelena S. Quercetin in the treatment of dyslipidemia. Med Arh. (2012)
71. Knab AM, et al. Quercetin with vitamin C and niacin does not affect body mass or composition. Appl Physiol Nutr Metab. (2011)
72. Knab AM, et al. Influence of quercetin supplementation on disease risk factors in community-dwelling adults. J Am Diet Assoc. (2011)
73. Boots AW, et al. Quercetin reduces markers of oxidative stress and inflammation in sarcoidosis. Clin Nutr. (2011)
74. Egert S, Rimbach G, Müller MJ. No evidence for a thermic effect of the dietary flavonol quercetin: a pilot study in healthy normal-weight women. Eur J Appl Physiol. (2011)

(Common misspellings for Quercetin include querctin, qurcetin, quercetn)

(Common phrases used by users for this page include quercitin good or bad, quercetin supplements 20mg, quercetin equivalent, quercetin dihydrate absorpyion, quercetin -what's it for?, quercertin supplements)

(Users who contributed to this page include KurtisFrank, Sol)