Quercetin

Quercetin/Drug Interactions:

  • Agents used in schizophreniaAgents used in schizophrenia: In human study, a complex of antioxidants, including quercetin, as well as enterosorbent, had a positive effect on the clinical course in patients with schizophrenia (42).
  • Antiarthritic agentsAntiarthritic agents: Based on evidence from patients with arthritis, quercetin may demonstrate antiarthritic effects (55).
  • Anticoagulant and antiplatelet agentsAnticoagulant and antiplatelet agents: Based on laboratory study, quercetin and the flavone apigenin may inhibit platelet aggregation and collagen- and ADP-induced aggregation (41; 6).
  • Antidiabetic agentsAntidiabetic agents: Based on human study, consumption of a low-calorie cranberry juice containing quercetin-3-galactoside may produce a favorable glycemic response and may be beneficial for persons with impaired glucose tolerance (56).
  • Antihypertensive agentsAntihypertensive agents: Based on animal and human evidence, quercetin supplementation may reduce blood pressure (8).
  • Anti-inflammatory agentsAnti-inflammatory agents: Based on human evidence, quercetin may exert anti-inflammatory properties (57; 58; 59), however, in one human study, daily oral supplementation of healthy humans with quercetin for two weeks did not affect inflammation (60). In laboratory studies, quercetin can inhibit activation of mast cells (52).
  • Antilipemic agentsAntilipemic agents: In human study, plasma lipids (triglycerides, total cholesterol, LDL- and HDL-cholesterol) did not change following supplementation with red wine extract or quercetin (61).
  • Antineoplastic agentsAntineoplastic agents: Based on in vitro and animal studies, quercetin may have anticarcinogenic, antiproliferative and antitumor properties (62; 63; 16; 19; 64; 65; 66; 67; 68; 69; 70). Negative interactions with agents taken for cancer are currently lacking, although a synergistic effect has been proposed (71; 72; 73).
  • AntiviralsAntivirals: Based on quercetin's effects against reverse transcriptase of HIV and other retroviruses (22), quercetin may reduce the infectivity and cellular replication of the herpes simplex virus, polio virus, parainfluenza virus and the respiratory syncytial virus.
  • BusulphanBusulphan: In human leukemia cell lines, quercetin enhanced the anti-proliferative activity of the chemotherapeutic agent, busulphan (71).
  • Cardiovascular agentsCardiovascular agents: Epidemiological studies report that quercetin supplementation is associated with a reduced risk of coronary heart disease/stroke and reduces blood pressure in hypertensive humans and rodents (8). A human cohort study did not find an association between flavonoid intake and the risk of coronary heart disease (74). However, based on mechanism of action, quercetin consumption may have an inhibitory effect on developmentof aortic atherosclerotic lesions and on atherogenic modificationsof LDL injury by inhibiting lipoprotein oxidation or directly protecting cells from oxidized low-density lipoproteins (75; 76; 36). The effects may be mediated by the metabolites of quercetin (77).
  • CisplatinCisplatin: In cell cultures, quercetin inhibited the repair of cisplatin-induced DNA damage in hepatocytes (72), and it inhibited cisplatin-induced damage to cultured renal tubular epithelial cells, possibly through free radical scavenging (78).
  • CorticosteroidsCorticosteroids: Inhibition of cytochrome P450 activity by quercetin may contribute to sustaining blood levels of corticosteroids (79).
  • CyclosporineCyclosporine: Quercetin may affect the pharmacokinetics of oral cyclosporine (80).
  • Cytochrome P450 metabolized agentsCytochrome P450 metabolized agents: Given the antioxidant effect of quercetin, as well as other flavonoids, it may be a significant source of inhibitors of drug oxidation and may theoretically interact with drugs that are metabolized by the CYP3A4 pathway. Flavonoids, such as quercetin, interact with the metabolism of drugs such as 17 beta-estradiol and other steroids that are extensively metabolized through the P-450NF (P-450 IIIA4) enzyme or closely related P450 systems (81).
  • EstradiolEstradiol: Laboratory studies suggest that quercetin, an inhibitor of the cytochrome P450 enzyme system, may inhibit the metabolism of estradiol, but this has not been found to be of clinical significance (79). One study found quercetin to be a pure estrogen antagonist (82).
  • Gastrointestinal agents, miscellaneousGastrointestinal agents, miscellaneous: In patients with acute diarrheic disease, the phytodrug QG-5, developed from guava leaves and standardized in its content of quercetin, decreased the duration of abdominal pain (17).
  • Hepatic agentsHepatic agents: Based on laboratory study, quercetin may inhibit xanthine oxidase and the proliferation of hepatic stellate cells (83; 84).
  • NifedipineNifedipine: Food rich in flavonoids, including quercetin, have been found to delay the first pass metabolism of nifedipine in humans; however, this effect cannot be specifically related to quercetin (43).
  • Quinolone antibioticsQuinolone antibiotics: Based on laboratory study, quercetin may bind to the DNA gyrase site on bacteria and competitively inhibit quinolone antibiotics (85).

    • Quercetin/Herb/Supplement Interactions:

  • Agents used in schizophreniaAgents used in schizophrenia: In human study, a complex of antioxidants, including quercetin, as well as enterosorbent, had a positive effect on the clinical course in patients with schizophrenia (42).
  • Antiarthritic herbs and supplementsAntiarthritic herbs and supplements: Based on evidence from patients with arthritis, quercetin may demonstrate antiarthritic effects (55).
  • Anticoagulants and antiplateletsAnticoagulants and antiplatelets: Based on laboratory study, quercetin and the flavone apigenin may inhibit platelet aggregation and collagen- and ADP-induced aggregation (41; 6).
  • Anti inflammatory herbsAnti inflammatory herbs: Based on human evidence, quercetin may exert anti-inflammatory properties (57; 58; 59), however, in one human study, daily oral supplementation of healthy humans with quercetin for two weeks did not affect inflammation (60). In laboratory studies, quercetin can inhibit activation of mast cells (52).
  • AntilipemicsAntilipemics: In human study, plasma lipids (triglycerides, total cholesterol, LDL- and HDL-cholesterol) did not change following supplementation with red wine extract or quercetin (61).
  • AntineoplasticsAntineoplastics: Based on in vitro and animal studies, quercetin may have anticarcinogenic, antiproliferative and anti-tumor properties (62; 63; 16; 19; 64; 65; 66; 67; 68; 69; 70). Negative interactions with agents taken for cancer are currently lacking, although a synergistic effect has been proposed (71; 72; 73).
  • AntioxidantsAntioxidants: Based on in vitro and in vivo studies, quercetin may have antioxidant effects (46; 61; 45; 23; 31; 86) (10). Although, contrary to animal-based studies, there was no quercetin-evoked reduction in markers of oxidative stress in three human studies (8; 87; 60).
  • AntiviralsAntivirals: Based on quercetin's effects against reverse transcriptase of HIV and other retroviruses (22), quercetin may reduce the infectivity and cellular replication of the herpes simplex virus, polio virus, parainfluenza virus and the respiratory syncytial virus.
  • Bilberry,lingonberry, black currantsBilberry,lingonberry, black currants: Consumption of black currants, lingonberries and bilberries increases serum quercetin concentrations (88).
  • BromelainBromelain: Based on a human controlled trial, use of bromelain may increase the gastrointestinal absorption of quercetin (40).
  • Cardiovascular herbs and supplementsCardiovascular herbs and supplements: Epidemiological studies report that quercetin supplementation is associated with a reduced risk of coronary heart disease/stroke and reduces blood pressure in hypertensive humans and rodents (8). A human cohort study did not find an association between flavonoid intake and the risk of coronary heart disease (74). However, based on mechanism of action, quercetin consumption may have an inhibitory effect on developmentof aortic atherosclerotic lesions and on atherogenic modificationsof LDL injury by inhibiting lipoprotein oxidation or directly protecting cells from oxidized low-density lipoproteins (75; 76; 36). The effects may be mediated by the metabolites of quercetin (77).
  • Cytochrome P450 metabolized herbs and supplementsCytochrome P450 metabolized herbs and supplements: Given the antioxidant effect of quercetin, as well as other flavonoids, it may be a significant environmental source of inhibitors of drug oxidation, and may interact with agents that are metabolized by the CYP3A4 pathway (81).
  • ElderElder: Consumption of elder increases serum quercetin concentrations.
  • Gastrointestinal herbs and supplementsGastrointestinal herbs and supplements: In patients with acute diarrheic disease, the phytodrug QG-5, developed from guava leaves and standardized in its content of quercetin, decreased the duration of abdominal pain (17).
  • Ginkgo bilobaGinkgo biloba: Consumption of Ginkgo biloba increases serum quercetin concentrations.
  • Green teaGreen tea: Consumption of green tea increases serum quercetin concentrations.
  • Hepatic agentsHepatic agents: Based on laboratory study, quercetin may inhibit xanthine oxidase and the proliferation of hepatic stellate cells (83; 84).
  • HypotensivesHypotensives: Quercetin supplementation reduced blood pressure in hypertensive rodents and hypertensive humans (8).
  • PapainPapain: Use of papain in combination with quercetin may increase the gastrointestinal absorption of quercetin, as seen by increased improvement in symptoms of chronic pelvic pain syndrome in a controlled trial (40).
  • Parsley (Petroselinum crispum)Parsley (Petroselinum crispum): Due to quercetin content, consumption may cause additive effects.
  • Rutin containing herbsRutin containing herbs: Due to quercetin content, consumption may cause additive effects.
  • St. John's wortSt. John's wort: Due to quercetin content, consumption may cause additive effects.
  • Vitamin CVitamin C: Positive interaction: Vitamin C may enhance the antioxidant activity of quercetin as represented in vitro as additive reductions in oxidative DNA damage (33; 54).

    • Quercetin/Food Interactions:

  • GeneralGeneral: Food may decrease or delay absorption of quercetin; therefore, it has been recommended to take quercetin on an empty stomach (anecdotal).
  • ApplesApples: Due to quercetin content, consumption may cause additive effects (89).
  • BerriesBerries: Consumption of black currants, lingonberries and bilberries increases serum quercetin concentrations (88). Three doses of black currant and apple (1:1) juice (750, 1000, and 1,500mL) for one week corresponding to an intake of 4.8, 6.4, and 9.6mg quercetin per day (46).
  • Brassica vegetables (cabbage broccoli, cauliflower, turnips, kale)Brassica vegetables (cabbage, broccoli, cauliflower, turnips, kale): Due to quercetin content, consumption may cause additive effects.
  • GlucoseGlucose: Absorption is enhanced by conjugation with glucose (31).
  • GrapefruitGrapefruit: Due to quercetin content, consumption may cause additive effects.
  • OnionsOnions: Quercetin supplementation may have an additive effect when consumed with other quercetin-containing foods, such as onions (15) (90). Substantial amounts of quercetin can be ingested through the consumption of foods rich in plant polyphenols (41; 46).
  • Red wineRed wine: Due to quercetin content, consumption may cause additive effects.
  • Rutin containing foodsRutin containing foods: Due to quercetin content, consumption may cause additive effects.

    • Quercetin/Lab Interactions:

  • Antioxidant capacityAntioxidant capacity: Measurements of antioxidant capacity (fasting plasma FRAP and PAR) and oxidative stress (fasting urinary 8-isoprostane F2a concentration) in humans were not altered with quercetin supplementation (8; 60).
  • Blood glucoseBlood glucose: Absorption is enhanced by conjugation with glucose (31). Fasting blood glucose levels did not change following quercetin supplementation in one clinical trial (8).
  • Blood pressureBlood pressure: Blood pressure was not altered in prehypertensive patients after quercetin supplementation, however, significant reductions in systolic, diastolic, and mean arterial pressures were observed in stage 1 hypertensive patients (8).
  • Cholesterol and triglyceride levelsCholesterol and triglyceride levels: Concentrations of plasma triglycerides and LDL, oxidized LDL, VLDL, HDL cholesterol, weight, BMI, heart rate, and the total cholesterol:HDL cholesterol ratio did not change after quercetin supplementation in humans (8; 60).
  • Hypertension markersHypertension markers: Quercetin supplementation in humans caused a significant reduction in plasma endothelin-1 concentration and significantly decreased the urinary endothelin-1 concentration (91).
  • Lipid peroxidation markersLipid peroxidation markers: Quercetin supplementation in humans did not change plasma or urinary F(2)-isoprostane concentrations (91).
  • Nitrate and nitrite levelsNitrate and nitrite levels: Quercetin supplementation in humans caused a significant increase in plasma S-nitrosothiols, plasma nitrite, and urinary nitrate concentrations, but not in plasma nitrate or urinary nitrite (91).