What is Quercetin?
This post was written with Consensus AI Academic Search Engine – please read our Disclaimer at the end of this article. Quercetin is a naturally occurring flavonoid found in a variety of fruits, vegetables, and grains. It is known for its potent antioxidant, anti-inflammatory, and therapeutic properties. This article explores the various health benefits and potential therapeutic applications of quercetin based on recent scientific research. Other names include: 3,3′,4’5,7-Pentahydroxyflavone, Bioflavonoid, Bioflavonoid Complex, Bioflavonoid Concentrate, Bioflavonoid Extract, Bioflavonoïde, Bioflavonoïde de Citron, Bioflavonoïdes de Citron, Citrus Bioflavones, Citrus Bioflavonoid, Citrus Bioflavonoids, Citrus Bioflavonoid Extract, Citrus Flavones, Citrus Flavonoids, Complexe de Bioflavonoïde, Concentré de Bioflavonoïde, Extrait de Bioflavonoïde, Extrait de Bioflavonoïdes de Citron, Flavones de Citron, Flavonoid, Flavonoïde, Meletin, Mélétine, Quercetina, Quercétine, Sophretin, Sophrétine.
Health Benefits of Quercetin
Cardiovascular Health
Quercetin has been shown to have significant benefits for cardiovascular health. A study demonstrated that quercetin supplementation can reduce blood pressure in individuals with stage 1 hypertension. The study involved a randomized, double-blind, placebo-controlled, crossover trial where participants received 730 mg of quercetin daily for 28 days. The results indicated a reduction in systolic, diastolic, and mean arterial pressures in hypertensive patients, although no significant changes were observed in prehypertensive individuals1.
Anti-Inflammatory and Wound Healing
Quercetin also exhibits strong anti-inflammatory properties. Research has shown that quercetin can promote diabetic wound healing by modulating macrophage polarization from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype. This modulation helps in reducing inflammation and accelerating wound repair in diabetic rats2.
Mitochondrial Biogenesis and Exercise Tolerance
Quercetin has been found to enhance mitochondrial biogenesis and improve exercise tolerance. In a study involving mice, quercetin supplementation increased the expression of genes associated with mitochondrial biogenesis in skeletal muscle and brain. This was accompanied by improved endurance capacity and voluntary wheel-running activity, suggesting potential benefits for athletic performance and chronic disease prevention3.
Rheumatoid Arthritis
Quercetin has shown promise as a therapeutic agent for rheumatoid arthritis (RA). In a collagen-induced arthritis model in mice, quercetin treatment resulted in reduced joint inflammation and decreased levels of pro-inflammatory cytokines. The study concluded that quercetin could be a potential alternative treatment for RA due to its anti-inflammatory and protective effects4.
Cancer Prevention
Quercetin has been investigated for its chemopreventive properties against prostate cancer. In an in vivo study, quercetin supplementation inhibited the EGFR signaling pathway, which is crucial for cancer cell proliferation. The study found that quercetin reduced the expression of proteins associated with cancer progression, suggesting its potential as a chemopreventive agent5.
Gastrointestinal Health
Quercetin has beneficial effects on gastrointestinal health, particularly in reducing intestinal inflammation and pyroptosis. A study demonstrated that quercetin could ameliorate lipopolysaccharide (LPS)-induced intestinal inflammation by modulating the TLR4/NF-κB/NLRP3 signaling pathway. This resulted in reduced expression of inflammatory markers and improved intestinal barrier function6.
Metabolic Health
Quercetin has been shown to improve glucose and lipid metabolism in models of metabolic disorders. In a study involving monosodium glutamate (MSG)-induced obesity in rats, quercetin treatment normalized lipid profiles, reduced body weight, and improved antioxidant status. These effects were attributed to quercetin’s ability to modulate metabolic and hormonal profiles7.
COVID-19
Quercetin has been explored as a complementary treatment for early-stage COVID-19. A clinical trial found that quercetin supplementation in outpatients with mild to moderate COVID-19 symptoms resulted in faster recovery and reduced viral load. The study suggested that quercetin could modulate the host’s hyperinflammatory response, aiding in the early resolution of symptoms8.
Lead Toxicity
Quercetin has protective effects against lead toxicity. In a study with male Wistar rats, quercetin supplementation mitigated the oxidative stress induced by lead exposure. The study found improvements in hematological and biochemical parameters, indicating quercetin’s potential as an antioxidant to counteract lead toxicity9.
Polycystic Ovary Syndrome (PCOS)
Quercetin has been investigated for its therapeutic potential in polycystic ovary syndrome (PCOS). A study found that quercetin improved hormonal and metabolic disturbances in a rat model of PCOS. The beneficial effects were linked to the modulation of the AMPK/SIRT-1 axis and regulation of adipose tissue hormones10.
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Adverse Effects of Quercetin
Gastrointestinal Issues
Mild adverse events such as gastro-oesophageal reflux disease have been reported in both placebo and quercetin groups, indicating that quercetin may cause mild gastrointestinal discomfort7.
Impact on Serum Elements
Quercetin administration in depressed rats showed significant changes in serum elements, including increased levels of iron, copper, and calcium, and decreased levels of magnesium, zinc, selenium, and cobalt. These alterations suggest potential metabolic imbalances10.
No Severe Adverse Effects in Specific Contexts
In studies involving patients with chronic obstructive pulmonary disease (COPD) and overweight subjects with high cardiovascular disease risk, quercetin was well-tolerated with no severe adverse effects reported. Blood parameters of liver and kidney function, haematology, and serum electrolytes did not reveal any adverse effects7 8.
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How has Quercetin Improved Patient Outcomes?
Cardiovascular Health
Quercetin supplementation significantly increased total antioxidant capacity (TAC) and improved the insecurity dimension of quality of life in post-myocardial infarction patients, although it did not significantly affect other inflammatory factors or blood pressure1.
In patients with myocardial infarction and type 2 diabetes, quercetin combined with adenosine and standard treatment improved cardiac function and quality of life more than standard treatment alone6.
Renal Transplantation
Quercetin, in combination with curcumin, improved early graft function and reduced acute rejection rates in cadaveric renal transplantation patients2.
COVID-19
Quercetin Phytosome® supplementation in early-stage COVID-19 patients led to faster virus clearance, reduced symptom severity, and improved inflammatory markers compared to standard care alone3 4.
Rheumatoid Arthritis
Quercetin supplementation reduced early morning stiffness, pain, and disease activity in women with rheumatoid arthritis, along with a significant reduction in plasma levels of high-sensitivity tumor necrosis factor-α (hs-TNFα)5.
Wound Healing
Quercetin promoted diabetic wound healing by modulating macrophage polarization from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype, thereby accelerating wound repair9.
Stroke and Brain Injury
In a rat model of cerebral ischemia, quercetin reduced blood-brain barrier disruption, brain edema, and matrix metalloproteinase-9 (MMP-9) activity, leading to improved functional outcomes8.
Chronic Obstructive Pulmonary Disease (COPD)
Quercetin was found to be safe and well-tolerated up to 2000 mg/day in patients with COPD, with no severe adverse events reported10.
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Quercetin Mechanisms of Action
Antioxidant and Anti-inflammatory Effects
Quercetin reduces oxidative stress by scavenging reactive oxygen species (ROS) and enhancing the activity of endogenous antioxidant enzymes like superoxide dismutase (SOD) and glutathione reductase (GSH)1 5 7 8 10.
It inhibits the activation of the NF-κB pathway, which is crucial for inflammatory responses, thereby reducing inflammation5 7 10.
Modulation of Enzyme Activities
Quercetin boosts nitric oxide (NO) levels and modulates the activities of enzymes such as arginase, acetylcholinesterase (AChE), and adenosine deaminase (ADA), which are linked to smooth muscle relaxation and sexual function1.
It increases the activity of cholesterol 7α-hydroxylase, promoting the conversion of cholesterol to bile acids and enhancing cholesterol efflux via ATP binding cassette transporter G1 (ABCG1)2.
Regulation of Signaling Pathways
Quercetin inhibits the NLRP3 inflammasome activation, reducing the production of proinflammatory cytokines and attenuating tissue damage in conditions like spinal cord injury3.
It modulates the Nrf2/HO-1 pathway, enhancing antioxidant defenses and reducing oxidative stress and inflammation in various tissues, including the liver and brain5 7 10.
Cellular and Molecular Effects
Quercetin promotes the polarization of macrophages from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype, aiding in wound healing and reducing chronic inflammation4.
It inhibits the EGFR signaling pathway, reducing the expression of proteins involved in cell proliferation and cancer progression, such as PCNA, N-cadherin, vimentin, and cyclin D16.
Protective Effects in Disease Models
Quercetin prevents myocardial infarction-induced left ventricular remodeling by reducing fibrosis and oxidative stress, and by modulating the TGF-β1/Smad3 signaling pathway5.
It ameliorates vascular remodeling in hypertension by reducing oxidative stress and the activity of matrix metalloproteinase-2 (MMP-2)9.
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Common Complaints Associated with Quercetin Use
Minor Adverse Effects
In a study on the effects of quercetin on allergic reactions, minor notable adverse effects were reported throughout the study period, although specific details on the nature of these adverse effects were not provided2.
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Disclaimer
The content presented in this blog is generated by Consensus, an AI-powered academic search engine, and is based on publicly available scientific literature. While every effort is made to provide accurate, up-to-date, and well-researched information, the content is intended for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making any decisions regarding medical conditions, treatments, or medications. The AI system’s analysis may not cover all perspectives, emerging research, or individual cases, and it is not a substitute for professional expertise. Neither the blog publisher nor the developers of the AI-powered search engine are responsible for any actions taken based on the information provided in this content. Use of this information is at your own risk. Citations to the original scientific studies are included for reference, but these studies should be reviewed in full and interpreted with the guidance of a healthcare or research professional.
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