Named Bioactive Compounds · Compound
Quercetin (Flavonoid)
Strong Evidencecompound
Hermetica Superfood Encyclopedia
Quercetin is a prominent naturally occurring flavonoid renowned for its potent antioxidant and anti-inflammatory properties. It primarily acts by scavenging free radicals, chelating metals, and inhibiting inflammatory enzymes like COX and LOX.
Quercetin is a pentahydroxyflavone (3,5,7,3',4'-pentahydroxyflavone) naturally occurring in fruits, vegetables, and herbs such as onions, apples, and dill, where it exists predominantly as glycosides like quercetin-3-O-β-glucoside. Plants synthesize quercetin as a defense against UV radiation and oxidative stress, and commercial extraction typically involves solvent methods or enzymatic processes to yield the aglycone from glycosylated forms.
The research dossier contains no specific human clinical trials, RCTs, or meta-analyses for quercetin. While general references note antioxidant and potential anticancer properties, no clinical trial data, PMIDs, study designs, or outcomes are provided in the available research.
No clinically studied dosage ranges, forms, or standardization details are provided in the research dossier. Consult a healthcare provider before starting any new supplement.
Quercetin is a pure flavonoid compound (aglycone form), not a whole food, so macronutrient and micronutrient framing is not applicable in the traditional sense. As an isolated bioactive compound: Molecular formula C15H10O7, molecular weight 302.24 g/mol. It is a polyphenolic flavonol characterized by a 3-hydroxyflavone backbone with a catechol (o-dihydroxyl) group on the B-ring at positions 3' and 4', a hydroxyl at position 3 on the C-ring, and additional hydroxyls at positions 5 and 7 on the A-ring. Contains no protein, fat, or digestible carbohydrates. Caloric contribution is negligible at typical supplemental doses (typically 250–1000 mg/day in research contexts). Naturally occurs in foods primarily as glycosides (quercetin-3-glucoside, quercetin-3-rutinoside/rutin, quercetin-3-galactoside) rather than the free aglycone; representative food concentrations include capers (dry) ~234 mg/100g, capers (canned) ~173 mg/100g, lovage leaves ~170 mg/100g, radish leaves ~70 mg/100g, carob fiber ~58 mg/100g, dill ~55 mg/100g, red onion ~32 mg/100g, kale ~7–23 mg/100g, broccoli ~3 mg/100g, apple with skin ~4 mg/100g, and blueberries ~3 mg/100g. Bioavailability is highly form-dependent: the aglycone form has estimated oral bioavailability of approximately 1–3% in humans due to poor aqueous solubility and first-pass metabolism; quercetin glycosides show moderately higher bioavailability (approximately 3–7%) as intestinal lactase-phlorizin hydrolase and gut microbiota cleave the sugar moieties to release the aglycone for absorption. Peak plasma concentrations following a 100 mg oral dose of quercetin aglycone reach approximately 0.1–0.3 µmol/L. Plasma half-life is approximately 11–28 hours. Extensively metabolized to isorhamnetin, tamarixetin, and kaempferol by hepatic O-methylation (COMT), and to sulfate and glucuronide conjugates; colonic microbiota further degrade unabsorbed quercetin to phenolic acids including 3,4-dihydroxyphenylacetic acid and 3-hydroxyphenylacetic acid. Lipid-based or nanoparticle formulations can increase bioavailability 2–5 fold relative to standard powder. No significant vitamin, mineral, or fiber content as an isolated compound.
Quercetin exerts its therapeutic effects primarily as a polyphenolic flavonoid by scavenging reactive oxygen species (ROS) and nitric oxide (NO), and chelating metal ions, thereby reducing oxidative stress. It also inhibits key inflammatory enzymes such as cyclooxygenase (COX) and lipoxygenase (LOX), leading to decreased production of prostaglandins and leukotrienes. Furthermore, quercetin modulates signal transduction pathways, binds to specific enzymes and receptors, and integrates into cell membrane lipid bilayers to exert its diverse biological activities.
Clinical trials have demonstrated quercetin's efficacy in cardiovascular health, specifically in reducing blood pressure and improving vascular reactivity. Human and animal studies consistently confirm its significant anti-inflammatory effects, primarily through the suppression of NF-κB and COX pathways. Research further supports its role in modulating immune responses, contributing to allergy relief and enhancing overall immune system responsiveness. While various study designs exist, consistent findings across multiple models underscore its broad therapeutic potential.
Quercetin is generally considered safe for most individuals at typical supplemental doses; however, mild side effects such as headache or stomach upset may occur. It may interact with certain medications, including anticoagulants like warfarin, some antibiotics, and cyclosporine, potentially altering their effects. Individuals with kidney disease, or those who are pregnant or breastfeeding, should consult a healthcare professional before use due to limited safety data in these populations. Always disclose quercetin use to healthcare providers to prevent potential interactions.
