Quercetin is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.
Table of Contents
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Natural Sources
Source | Quantity of Quercetin Present |
---|---|
Apple juice | 2.5 mg/L [14] |
Apples | 0.0263% [13] |
Brussel Sprout | 0.0025% [13] |
Cabbage | 0.01% [13] |
Cauliflower | 0.0006% [13] |
Cayenne | 0.0063% [13] |
Chives | 0.0009% [13] |
Chocolate milk | 1.3 mg/L [14] |
Cranberry | 0.025% [13] |
Evening Primrose | 20% [13] |
Garlic | 0.02% [13] |
Grape juice | 4.4 mg/L [14] |
Grapefruit juice | 4.9 mg/L [14] |
Himalayan Mayapple | 1.2% [13] |
Kale | 0.005% [13] |
Kohlrabi | 0.002% [13] |
Lemon juice | 7.4 mg/L [14] |
Mayapple | 5% [13] |
Neem | 0.1% [13] |
Oats | 0.031% [13] |
Onions | 4.81% [13] |
Orange juice | 3.4-5.7 mg/L [14] |
Pear | 0.0028% [13] |
Spinach | 0.0019% [13] |
Tea | 1% [13] |
Tea | 10-25 mg/L [14] |
Tomato juice | 13 mg/L [14] |
Effects on Estradiol 17beta-dehydrogenase Type 2
In vitro quercetin was found to be a potent inhibitor of oxidative Estradiol 17beta-dehydrogenase Type 2 (17b-HSD2) where it prevented the oxidation of estradiol to estrone. The IC50 was determined to be 1.5 µM.[11][12]
Blocking Psychedelic Action of Allylbenzenes
Anecdotal reports indicate that pre-treatment with quercetin can block or delay the onset of the psychedelic effects of allylbenzenes by 3-4 hours.
Quercetin is known to potently inhibit oxidative Estradiol 17beta-dehydrogenase Type 2.
Evidence indicates that allylbenzenes require oxidation by Estradiol 17beta-dehydrogenase Type 2 before they can form 1'-oxo metabolites (such as 1'-oxoestragole from methyl chavicol). Many studies indicate that only the 1'-oxo metabolites of allylbenzenes are able to form alkaloids.
See the articles Estradiol 17beta-dehydrogenase Type 2, Oilahuasca Activation, 1'-oxoestragole, and 1'-oxosafrole for more information.
Effects on N-Acetyltransferase
500 mg of quercetin taken orally in humans was found to induce N-acetyltransferase (NAT2) by 88.7%.[4]
Effects on Xanthine Oxidase
500 mg of quercetin taken orally in humans was found to induce xanthine oxidase (XO) activity by 15.0%.[4]
Effects on Monoamine Oxidase
In vitro quercetin inhibited Monoamine Oxidase B enzymes with an IC50 of 11-90.0 µM.[9][10] In vitro it inhibited Monoamine Oxidase A enzymes with an IC50 of 2.8 µM.[10]
Effects on Sulfotransferase (SULT)
In an in vitro test quercetin completely inhibited human SULT1A1 and partially inhibited SULT1A3.[7]
Effects on P-glycoprotein (P-gp)
One test showed that 500 mg of quercetin orally elevated the plasma concentrations of fexofenadine in humans. This action was believed to be caused by inhibition of P-gp.[6]
In one test where rats were fed quercetin, P-gp appeared to be induced. In vitro tests found that quercetin induced P-gp.[2] Another test found that only low doses induced P-gp while high doses inhibited P-gp in mice.[8]
Effects on Individual P450 Enzyme Levels
Quercetin is known as a potent CYP2C8 inhibitor, however it has no effect on CYP2C8 in humans.[1]
In rats fed quercetin, CYP3A4 appeared to be induced. In vitro tests found that quercetin induced CYP3A4.[2] Another test found quercetin inhibited CYP3A4 in rats.[3]
Enzyme | Interaction | Dosage | Verified In Humans |
---|---|---|---|
CYP1A1 | ? | ? | ? |
CYP1A2 | 10.4% inhibition[4] | 500 mg | Yes [4][5] |
CYP1B1 | ? | ? | ? |
CYP2A6 | ? | ? | ? |
CYP2B6 | 25.3% induction[4] | 500 mg | Yes |
CYP2C8 | No Effect[1] | ? | Yes |
CYP2C9 | ? | ? | ? |
CYP2C19 | ? | ? | ? |
CYP2D6 | ? | ? | ? |
CYP2E1 | ? | ? | ? |
CYP2F1 | ? | ? | ? |
CYP2J2 | ? | ? | ? |
CYP3A4 | Induction [2], Inhibition [3] | ? | ? |
Chemical Properties
PubChem Compound ID: 5280343
Molecular Weight: 302.2357 [g/mol]
Molecular Formula: C15H10O7
XLogP3: 1.5
H-Bond Donor: 5
H-Bond Acceptor: 7
IUPAC Name: 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one
InChI: InChI=1S/C15H10O7/c16-7-4-10(19)12-11(5-7)22-15(14(21)13(12)20)6-1-2-8(17)9(18)3-6/h1-5,16-19,21H
InChIKey: REFJWTPEDVJJIY-UHFFFAOYSA-N
Canonical SMILES: C1=CC(=C(C=C1C2=C(C(=O)C3=C(C=C(C=C3O2)O)O)O)O)O