What Is Quercetin?

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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?

Quercetin (3,3′,4′,5,7-pentahydroxyflavone) is the most abundant dietary flavonoid and one of the most extensively studied plant compounds for human health. It belongs to the flavonol subclass of flavonoids and is found in a wide variety of fruits, vegetables, leaves, and grains.

Quercetin is found in nature primarily in glycoside form (bound to sugar molecules), while commercial supplements typically use the aglycone form (quercetin dihydrate) for higher potency and standardization.

The global quercetin market is valued at approximately USD 150-180 million (2024) and is growing at 8-11% CAGR, driven by increasing consumer awareness of immune support, antioxidant supplementation, and natural anti-inflammatory ingredients.

Natural Sources and Commercial Extraction Plants

Extraction Methods

Rutin Extraction → Hydrolysis to Quercetin (Industry Standard)

The dominant commercial pathway for quercetin production:

Process Flow:

1. Raw material preparation — Dried Sophora japonica buds are cleaned and milled

2. Hot water extraction — Rutin is extracted with hot water (80-95°C)

3. Filtration — Plant debris removed

4. Crystallization — Rutin crystallizes upon cooling

5. Acid hydrolysis — Rutin is hydrolyzed with food-grade acid (HCl or citric acid) at 80-100°C

6. Neutralization — Hydrolysis mixture is neutralized

7. Quercetin crystallization — Quercetin precipitates and is collected

8. Purification — Recrystallization to achieve ≥95% purity

9. Drying — Produces quercetin dihydrate powder

Overall yield: Approximately 10-15% quercetin from Sophora japonica buds (via rutin intermediate)

Direct Extraction from Onion Waste

An emerging sustainable sourcing route:

• Source: Onion processing waste (skin, outer layers)

• Method: Ethanol or acetone-water extraction followed by purification

• Advantage: Circular economy, food waste valorization

• Challenge: Lower concentration requires larger-scale processing

• Best for: Brands emphasizing sustainability and "upcycled" ingredients

Standardization Grades and Specifications

Common Quercetin Grades

Quality Specification Sheet (Quercetin Dihydrate, ≥95%)

The Bioavailability Challenge — and Solutions

Why Quercetin Has Limited Absorption

Quercetin's aglycone form faces absorption barriers:

1. Low water solubility — Approximately 0.01 mg/mL in water at 25°C

2. Extensive first-pass metabolism — Rapid glucuronidation and sulfation in the intestine and liver

3. P-glycoprotein efflux — Actively pumped back into the intestinal lumen

Unformulated quercetin aglycone has oral bioavailability estimated at 1-5%, though this varies significantly by individual.

Bioavailability Enhancement Technologies

Mechanism of Action

Immune System Modulation

Quercetin's most well-researched mechanism is its effect on immune cell function:

Mast Cell Stabilization
    │
    ├── Quercetin inhibits mast cell degranulation
    ├── Blocks histamine release
    ├── Inhibits IgE-mediated allergic response
    └── Reduces inflammatory mediator release
         ├── Histamine ↓
         ├── Leukotrienes ↓
         ├── Prostaglandins ↓
         └── Cytokines (TNF-α, IL-6) ↓

Zinc Ionophore Activity
    │
    ├── Quercetin facilitates zinc entry into cells
    ├── Intracellular zinc inhibits viral replication
    └── Synergistic with zinc supplementation
         └── Particularly relevant for immune defense during viral seasons

Antioxidant Activity

Quercetin is one of the most potent antioxidant flavonoids:

• Direct ROS scavenging — Neutralizes superoxide, hydroxyl radical, peroxynitrite

• Metal chelation — Binds iron and copper, preventing Fenton reaction

• Enzyme modulation — Inhibits xanthine oxidase (uric acid production), LOX, COX

• Nrf2 activation — Upregulates endogenous antioxidant defense systems

• Vitamin C regeneration — Recycles oxidized vitamin C back to active form

Anti-Inflammatory Pathways

Clinical Evidence Summary

Applications in Product Formulation

Immune Support Supplements

Allergy & Respiratory Support

• Quercetin + Bromelain — Classic combination for seasonal allergy support

• Quercetin + Vitamin C — Mast cell stabilization + antioxidant synergy

• Quercetin + NAC — Comprehensive respiratory support formula

Sports Nutrition

• Post-workout recovery — 500-1,000 mg quercetin for exercise-induced inflammation

• Endurance formulas — Combined with electrolytes and carbohydrates

• Anti-inflammatory blends — With Curcumin and Boswellia for joint health

Combination Synergies

Sourcing Considerations for B2B Buyers

Key Questions for Suppliers

1. What is the source plant? — Sophora japonica vs. onion-derived; affects purity profile and marketing

2. What is the final purity? — ≥95% for standard supplements; ≥98% for pharmaceutical use

3. Is rutin residual content tested? — High rutin residual indicates incomplete hydrolysis

4. Is heavy metal testing comprehensive? — Particularly lead and cadmium

5. Can you provide isoquercitrin as an alternative? — For premium, higher-absorption formulations

Quality Red Flags

• Unusual color — Pure quercetin should be yellow to greenish-yellow powder; brown may indicate oxidation

• Low solubility in DMSO — Indicates possible adulteration with non-flavonoid materials

• Missing HPLC data — Quercetin chromatogram is essential for purity verification

Why Choose Greensky Bio as Your Quercetin Supplier

• GMP-certified production — ISO22000, BRCGS, Ecocert Organic Standard, SGS-GMP certified facilities

• Advanced testing capabilities — Independent laboratory with HPLC, GC, UV, ICP-MS for comprehensive quality control

• 20+ years experience — Established in 2004, with deep expertise in plant extract R&D and production

• Global market presence — Export to Europe, the United States, South Korea, and Russia

• Customized solutions — Ability to develop quercetin formulations per customer specifications

GreenSky Bio — Professional Natural Plant Extract Manufacturer Since 2004. For inquiries about quercetin and other antioxidant ingredients, contact our team.

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