Accurate Education – Quercetin

Widely distributed in the plant kingdom, quercetin is a flavonoid compound found in many plants and foods. Flavonoids are a group of compounds that  help regulate cellular activity and through their antioxidant effects fight off free radicals that cause oxidative stress. In simpler terms, they help the body function more efficiently while protecting it against everyday toxins and stressors.

Quercetin is the most abundant and most studied flavonoids (subgroup, flavonols) and is found in many foods. Onions are the most important sources of quercetin, but other vegetables including broccoli, asparagus, green peppers, tomatoes and red leaf lettuce, are great sources of quercetin, especially in the summer. Apples, strawberry, red raspberry, blueberry, cranberry and black currants, teas and wine are also considered abundant dietary sources of quercetin. While generally found at relatively low concentrations of 15–30 mg/kg (fresh weight), some vegetables such as onions and shallots have much more extensive content.

Quercetin and Pain

Quercetin supplements have strong preclinical and emerging clinical evidence for analgesic, anti-inflammatory, and neuroprotective benefits, including suppression of systemic inflammation, oxidative stress, and central sensitization mechanisms.

References

1. The Emerging Role of Quercetin in the Treatment of Chronic Pain. Liu C, Liu DQ, Tian YK, et al. Current Neuropharmacology. 2022;20(12):2346-2353. doi:10.2174/1570159X20666220812122437.
2. Quercetin Ameliorates CFA-Induced Chronic Inflammatory Hyperalgesia via Modulation of ROS-Mediated ERK1/2 Signaling and Inhibition of Spinal Glial Activation in Vivo. Kumar S, Vinayak M. Neuromolecular Medicine. 2020;22(4):517-533. doi:10.1007/s12017-020-08609-z.
3. Quercetin Inhibits Peripheral and Spinal Cord Nociceptive Mechanisms to Reduce Intense Acute Swimming-Induced Muscle Pain in Mice. Borghi SM, Pinho-Ribeiro FA, Fattori V, et al. PloS One. 2016;11(9):e0162267. doi:10.1371/journal.pone.0162267.
4. Advance in the Pharmacological Effects of Quercetin in Modulating Oxidative Stress and Inflammation Related Disorders. Zhou Y, Qian C, Tang Y, et al. Phytotherapy Research : PTR. 2023;37(11):4999-5016. doi:10.1002/ptr.7966.
5. Quercetin Reduces Inflammatory Pain: Inhibition of Oxidative Stress and Cytokine Production. Valério DA, Georgetti SR, Magro DA, et al. Journal of Natural Products. 2009;72(11):1975-9. doi:10.1021/np900259y.
6. Regulatory Effects of Quercetin on M1/M2 Macrophage Polarization and Oxidative/Antioxidative Balance. Tsai CF, Chen GW, Chen YC, et al. Nutrients. 2021;14(1):67. doi:10.3390/nu14010067.
7. The Potential Benefits of Quercetin for Brain Health: A Review of Anti-Inflammatory and Neuroprotective Mechanisms. Chiang MC, Tsai TY, Wang CJ. International Journal of Molecular Sciences. 2023;24(7):6328. doi:10.3390/ijms24076328.
8. Computational Analysis and in Vitro Verification Insights Into Quercetin’s Suppression of Neuroinflammation in BV-2 Microglia Through NF-κB Pathway Inhibition. Hsieh CY, Chuang CH, Gomez MC, et al. Current Medicinal Chemistry. 2025;:CMC-EPUB-151006. doi:10.2174/0109298673395813250901012530.
9. The Potential Neuroprotective Role of Free and Encapsulated Quercetin Mediated by miRNA Against Neurological Diseases. Benameur T, Soleti R, Porro C. Nutrients. 2021;13(4):1318. doi:10.3390/nu13041318.
10. Influence of the Neuroprotective Properties of Quercetin on Regeneration and Functional Recovery of the Nervous System. Fideles SOM, de Cássia Ortiz A, Buchaim DV, et al. Antioxidants (Basel, Switzerland). 2023;12(1):149. doi:10.3390/antiox12010149.
11. Bioactive Effects of Quercetin in the Central Nervous System: Focusing on the Mechanisms of Actions. Suganthy N, Devi KP, Nabavi SF, Braidy N, Nabavi SM. Biomedicine & Pharmacotherapy = Biomedecine & Pharmacotherapie. 2016;84:892-908. doi:10.1016/j.biopha.2016.10.011.

Synergistic effects of quercetin have with vitamin C, curcumin, omega-3’s and resveratrol

Quercetin demonstrates synergistic anti-inflammatory and analgesic effects when combined with vitamin C, curcumin, omega-3 fatty acids, and resveratrol, with clinical and preclinical evidence supporting enhanced efficacy beyond single-agent use, particularly for pain management and reduction of systemic inflammation.

Quercetin + Vitamin C:

A recent clinical trial and in vitro study demonstrated that high-dose vitamin C (1g) combined with low-dose bioflavonoids including quercetin showed synergistic antioxidant, anti-inflammatory, and antiplatelet effects compared to vitamin C alone or individual flavonoids. The combination exhibited the most potent antioxidant capacity and strongest anti-inflammatory activity, suggesting that quercetin enhances vitamin C’s biological effects through complementary molecular mechanisms. However, the flavonoid dose used may not have been sufficient to fully translate in vitro synergy to clinical outcomes, indicating that higher quercetin doses may be needed for optimal synergy.

Quercetin + Curcumin + Resveratrol:

A randomized controlled trial in knee osteoarthritis patients evaluated a polyphenol supplement containing curcumin, resveratrol, rosemary extract, and ascorbic acid (though not specifically quercetin) versus ascorbic acid alone. The polyphenol group demonstrated significantly greater pain reduction, improved physical function and quality of life, and decreased systemic inflammation compared to controls. The authors attributed pain relief to attenuation of systemic inflammation by the polyphenol combination, supporting the concept that combining multiple polyphenols provides synergistic anti-inflammatory benefits relevant to pain management.

5 key mechanisms by which quercetin and other polyphenols work together:

1. Enhancing bioavailability of each compound
2. Increasing antioxidant capacity
3. Interacting with gut microbiome
4. Targeting the same signaling pathways (e.g., NF-κB, MAPK) with additive effects, and
5. Targeting different but complementary signaling pathways. These mechanisms explain why combinations of quercetin, curcumin, resveratrol, and omega-3s can produce greater anti-inflammatory effects than single agents.

Quercetin + Omega-3 Fatty Acids:

While direct clinical trials of quercetin combined with omega-3s are limited, both compounds independently suppress pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) and oxidative stress through complementary mechanisms. Quercetin inhibits cytokine production and preserves glutathione, while omega-3s produce pro-resolving lipid mediators. Their combination would theoretically provide synergistic anti-inflammatory effects, though this requires clinical validation.

Mechanisms of Synergy in Pain Management:

Quercetin, curcumin, resveratrol, and omega-3s all target key pain pathways including neuroinflammation, oxidative stress, and central sensitization. Quercetin specifically reduces inflammatory pain by inhibiting oxidative stress and pro-nociceptive cytokine production (TNF-α, IL-1β), while also modulating GABAergic and opioidergic systems in chronic pain models. When combined with curcumin and resveratrol—which similarly suppress NF-κB, COX-2, and glial activation—the compounds provide multi-target inhibition of pain pathways, potentially achieving greater analgesic efficacy than single agents.

Clinical Evidence Summary:

The strongest clinical evidence for synergistic pain and anti-inflammatory benefits comes from the osteoarthritis trial using a curcumin-resveratrol-based polyphenol combination, which demonstrated significant pain relief and functional improvement. The vitamin C-quercetin combination shows promising in vitro synergy but requires higher doses for clinical translation. Direct clinical trials specifically evaluating quercetin combined with curcumin, resveratrol, and omega-3s for pain management are still lacking.

In summary, quercetin exhibits synergistic anti-inflammatory and analgesic effects when combined with vitamin C, curcumin, resveratrol, and omega-3 fatty acids through complementary molecular mechanisms targeting oxidative stress, cytokine production, and pain signaling pathways. Clinical evidence supports polyphenol combinations for pain relief in osteoarthritis, though optimal dosing and specific multi-compound formulations require further investigation.

Other Health Benefits

Quercetin has many beneficial effects on human health that include antiviral properties, cardiovascular support and protection of the gastrointestinal tract. Quercetin also stabilizes mast cells and may reduce the inflammation associated with severe infection. The benefits of quercetin can be enhanced by the co-administration of vitamin C.

Antiviral Properties

Quercetin has a broad range of antiviral properties which can potentially interfere at multiple steps with viral infection including suppression of virus entry into cells, virus replication aand viral protein assembly.  It stimulates the immune system and its broad range of antiviral properties has been suggested to potentially interfere with COVID-19 infection. Quercetin also targets viral polymerases and may disrupt replication via the inhibition of reverse transcriptase enzymes.

Anti-inflammatory and Anti-allergic Properties

Quercetin has strong anti-allergic properties through its inhibition of histamine production and release by mast cells. It has also been shown to suppress activation of NLRP3 inflammasome to reduce the inflammatory process. In addition, quercetin up-regulates the NF- B and Nrf2 pathways that stimulate intracellular productiom of antioxidants. (see NRF2 Activators).

Antioxidant Properties

A number of quercetin’s beneficial effects are due to its antioxidant activity. Quercetin scavenges free radicals and inhibits the oxidation of LDL cholesterol. Quercetin, especially when paired with vitamin C, reduces the incidence of oxidative damage to skin and nerves caused by glutathione depletion.

Mast Cell Stabilization

Probably the most well-known of quercetin’s mechanisms of action involves stabilization of mast cell membranes. Mast cells function as sentinels or guards that are able to sense a wide range of potential injury to the body such as infections or environmental toxins.  When a mast cell senses a threat, it “activates,” producing and releasing chemical “mediators” directed at assisting the body in managing the threat. These mediators include histamine, pro-inflammatory cytokines, leukotrienes, and interleukin IL-4. They are primary players in allergic reactions and the inflammatory responses to injury and infection.

In some cases, however, mast cell activation becomes dysregulated and the excessive or inappropriate release of mediators, especially histamine and pro-inflammatory cytokines, can lead to a wide range of symptoms and disease processes.

Inappropriate mast cell activation is linked to certain cancers, cardiovascular diseases, connective tissue disorders, allergy, asthma and irritable bowel syndrome (IBS). Mast cell dysregulation can drive seasonal allergies and auto-immune conditions such as rheumatoid arthritis (RA) and Lupus.  Mast cells and inflammation of the brain have been linked to depression, anxiety and other mental health conditions. They may also be linked to Ehler Danlos Syndrome, autonomic dysfunction (dysautonomia) celiac disease and Interstitial Cystitis (IC).

Mast Cell Activation Disease (MCAD) is an umbrella term that includes a collection of disorders characterized by (1) accumulation of genetically altered or dysregulated mast cells and/or (2) abnormal release of these cells’ mediators, including Mast Cell Activation Syndrome (MCAS). MCAS is a chronic multisystem disorder with inflammatory and allergic manifestations and is fairly common, with an estimated prevalence of 17% of the general population. MCAS is thought to be involved in the etiology of many medical conditions including idiopathic anaphylaxis, interstitial cystitis, some subsets of fibromyalgia and irritable bowel syndrome, as well as neurologic and psychiatric symptoms and diseases.

Quercetin stabilizes mast cells and suppresses mast cell activity including the creation of  leukotrienes, suppression of interleukin IL-4 production and inhibition of histamine and pro-inflammatory cytokines release. Evidence suggests that quercetin may have therapeutic benefit in the treatment of MCAS and related conditions characterized by mast cell dysregulation.

See: Mast Cell Activation Disease (MCAD)

Quercetin Synergy with Vitamin C

Quercetin’s therapeutic benefits can be enhanced by the co-administration of vitamin C. Vitamin C prevents the spontaneous degradation of quercetin and it also has the capacity to recycle quercetin, increasing its efficacy. Vitamin C and quercetin co-administration also exerts a synergistic antiviral action due to overlapping antiviral and immunomodulatory properties.

SARS-CoV-2 (COVID-19)

Vitamin C has a supportive role in the prevention and treatment of colds and viral inections. Quercetin and ascorbic acid co-administration is a strategy with current evidence supporting their use for prophylaxis and treatment of several respiratory viruses, including SARS-CoV-2 (COVID-19). Vitamin C and quercetin co-administration exerts a synergistic antiviral action due to overlapping antiviral and immunomodulatory properties. The blockage of virus entry represents a key strategy and quercetin impedes viral membrane fusion for both influenza and SARS-Cov.

Both quercetin and vitamin C have excellent safety profiles with a favorable risk to benefit ratio. Furthermore, based on their lack of severe side effects and low-costs, the combined administration of these two compounds for both the prophylaxis and the early treatment of respiratory tract infections, especially including COVID-19.

Quercetin Synergy with Zinc

Quercetin also chelates, or binds, to zinc and transports it into cells which could, theoretically, enhance the anti-viral actions of zinc.

Quercetin Supplements

Dietary quercetin has poor water solubility, chemical instability, and low oral bioavailability. Additionally, quercetin is digested (e.g., mouth, small intestine, liver, kidneys) it undergoes glucuronidation, sulfation, or methylation that further reduces its bioavailability. To overcome these issues, different formulations have been engaged to improve its stability, efficacy, and bioavailability. These formulations include phytosomal and nanoformulations, lipid-based carriers, micelles, metallic nanoparticles, inclusion complexes, and conjugate-based encapsulation. 

Phytosome Formulations of Quercetin

Phytosome complexes are created by a process that binds quercetin to a botanical extract of phosphatidylcholine, a key component of cell membranes. Phytosome complexes enhance the absorption of quercetin from the gut.

Nanformulations of Quercetin