Related Product

Quercetin

We are the leading quercetin manufacturer and also the leading supplier and exporter of quercetin. We specialize in providing natural and organic quercetin to meet your needs.

What Is Quercetin? Flavonoid Antioxidant Science, Immune Support & B2B Sourcing Guide (2026)

Quercetin is the most abundant and most studied dietary flavonoid in the human diet, found naturally in onions, apples, capers, broccoli, tea, and red wine. As a member of the flavonol subclass of polyphenols, Quercetin has emerged as one of the most commercially significant botanical ingredients in the global dietary supplement market — particularly for immune support, allergy management, and antioxidant protection.

With over 20 years of experience in natural plant extract manufacturing, Greensky Bio supplies premium quercetin in multiple forms (quercetin dihydrate, quercetin anhydrous, and quercetin phytosome), serving B2B formulators across Europe, the United States, South Korea, and Russia.

Quercetin Science: Why This Flavonoid Stands Out

While over 6,000 flavonoids have been identified in plants, quercetin (3,3′,4′,5,7-pentahydroxyflavone) is unique in its breadth of biological activity and clinical evidence base:

• Most widely consumed flavonoid — average dietary intake of 10–100mg/day

• Most studied flavonoid — over 10,000 peer-reviewed publications

• Broadest mechanism profile — antioxidant, anti-inflammatory, antiviral, anti-allergic, and cardioprotective

• Zinc ionophore activity — facilitates zinc transport into cells, enhancing zinc's antiviral effects

Molecular Mechanisms of Action

Clinically Supported Health Benefits

1. Immune System Support & Antiviral Defense

Quercetin's immune-modulating effects are among its most commercially important applications:

• Zinc Ionophore — Quercerin transports zinc ions across cell membranes, increasing intracellular zinc levels that inhibit viral RNA-dependent RNA polymerase — a mechanism critical for antiviral defense

• Anti-inflammatory Cytokine Modulation — Reduces production of pro-inflammatory cytokines (IL-6, TNF-α) while supporting balanced immune responses

• Upper Respiratory Health — A randomized controlled trial published in Medicine & Science in Sports & Exercise (2007) found that quercetin supplementation (1,000mg/day) reduced upper respiratory tract infection incidence and severity in middle-aged and older adults

2. Natural Antihistamine & Allergy Relief

Quercetin stabilizes mast cells and basophils, preventing the release of histamine and other inflammatory mediators. This makes it one of the most effective natural anti-allergy ingredients available:

• Mast Cell Stabilization — Inhibits IgE-mediated histamine release from mast cells

• Seasonal Allergy Support — Clinical evidence supports quercetin's effectiveness in reducing symptoms of allergic rhinitis (sneezing, nasal congestion, itchy eyes)

• Food Allergy Adjunct — May help reduce sensitivity reactions when used as part of a comprehensive approach

3. Cardiovascular Protection

Epidemiological studies consistently link higher quercetin intake with reduced cardiovascular disease risk:

• Blood Pressure — A meta-analysis in Critical Reviews in Food Science and Nutrition (2016) found quercetin supplementation significantly reduced systolic blood pressure (−4.4 mmHg) in hypertensive subjects

• LDL Protection — Prevents LDL oxidation, a key step in atherosclerosis development

• Endothelial Function — Improves nitric oxide-mediated vasodilation

4. Exercise Performance & Recovery

Quercetin's anti-inflammatory and mitochondrial-supportive effects make it valuable for athletes:

• Endurance Enhancement — Some studies show modest improvements in VO2 max and time-to-exhaustion

• Reduced Exercise-Induced Inflammation — Lowers post-exercise IL-6 and CRP levels

• Faster Recovery — Reduces muscle damage markers and DOMS after intense exercise

5. Anti-Aging & Senolytic Potential

Quercetin has gained attention as a senolytic compound — one that selectively eliminates senescent ("zombie") cells that accumulate with age and drive chronic inflammation. The combination of quercetin with dasatinib (a cancer drug) has shown senolytic activity in clinical trials, sparking significant research interest in quercetin's anti-aging potential.

Quercetin Forms: Choosing the Right Type for Your Product

Bioavailability Optimization: The Critical Challenge

Standard quercetin has notoriously poor oral bioavailability (<2%) due to low water solubility and extensive first-pass metabolism. B2B formulators should consider these proven strategies:

• Phytosome Technology — Quercetin bound to phosphatidylcholine shows up to 20× higher absorption than standard quercetin dihydrate

• Vitamin C Synergy — Co-administration with vitamin C can improve quercetin bioavailability by regenerating oxidized quercetin metabolites

• Piperine Enhancement — Adding Black Pepper Extract (piperine) inhibits glucuronidation, extending quercetin's half-life in circulation

• Liposomal Encapsulation — Lipid vesicle delivery protects quercetin through digestion and enhances cellular uptake

• Enzymatically Modified Isoquercitrin (EMIQ) — Water-soluble glycosylated form with significantly improved absorption

Standardization & Quality Specifications

At Greensky Bio, our ISO22000, BRCGS, Ecocert Organic, and SGS-GMP certified facility provides comprehensive COA documentation for every batch, tested using in-house HPLC, GC, and UV analytical instruments.

Quercetin Applications by Industry

Why Source Quercetin from Greensky Bio?

• Established 2004 — 20+ years of plant extract R&D and production

• Multiple forms available — dihydrate, anhydrous, and custom specifications

• Full certifications — ISO22000, BRCGS, Ecocert Organic, SGS-GMP

• In-house quality lab — HPLC verified ≥95% quercetin content per batch

• Global export experience — Europe, USA, South Korea, Russia (~$30M annual export)

• Competitive factory-direct pricing — no intermediaries, reliable supply

Frequently Asked Questions

What is the recommended daily dosage of quercetin?

Typical dosages range from 500–1,000mg per day of quercetin dihydrate. For immune support during cold/flu season, doses of 500–1,000mg twice daily are commonly used. For general antioxidant support, 250–500mg daily is sufficient.

Is quercetin safe for long-term use?

Quercetin is generally recognized as safe (GRAS) by the FDA. Human studies have used doses up to 1,000mg/day for periods up to 12 weeks without significant adverse effects. Higher doses may cause mild gastrointestinal discomfort in some individuals.

Can quercetin be combined with other supplements?

Yes. Quercetin is commonly and safely combined with vitamin C, zinc, bromelain, NAC, and Black Pepper Extract (piperine). These combinations often produce synergistic effects — for example, the quercetin + vitamin C + zinc combination is one of the most popular immune support formulations globally.

What is quercetin's zinc ionophore activity?

Quercetin can transport zinc ions across cell membranes, increasing intracellular zinc concentrations. Since zinc inhibits viral replication enzymes, this ionophore activity makes quercetin-zinc combinations particularly effective for immune and antiviral support.

Get a Quote for Quercetin

Whether you need standard 95% quercetin dihydrate for an immune support formula or high-bioavailability phytosome quercetin for a premium product, Greensky Bio provides certified, consistent quercetin at competitive prices.

Contact us today for samples, technical specifications, or a customized quote.