Benefits
20-Fold Improved Bioavailability vs Standard Quercetin
The Phytosome® delivery system solves quercetin's poor water solubility — the main reason unformulated quercetin shows <2% absorption from food. In a published pharmacokinetic clinical trial, Quercefit® demonstrated up to 20-fold greater oral bioavailability than unformulated quercetin at equivalent doses, with confirmed dose linearity. This translates to meaningful blood quercetin levels at supplemental doses that food simply cannot reach.
Allergic Rhinitis and Mild Asthma Symptom Relief
Allergic rhinitis and mild asthma symptom relief: in controlled trials in patients with mild-to-moderate asthma and rhinitis, Quercefit® at 250-500 mg/day reduced daytime symptoms by up to 50% and nighttime symptoms by up to 70% versus standard management alone, with reduced reliance on inhalers, nasal drops, and rescue medication. Reductions in eye itching, sneezing, nasal discharge, and sleep disturbance were confirmed for both seasonal and year-round allergens.
Exercise Performance and Recovery in Athletes
Exercise performance and recovery in athletes: in non-professional triathletes, Quercefit® 250 mg twice daily reduced run time from start to finish by 11.3% (vs 3.9% in controls). Post-exercise muscle discomfort, cramps, and recovery time all improved, and oxidative stress markers shifted favorably — one of the better-controlled ergogenic data points for any quercetin formulation.
Mild-to-Moderate COVID-19 Adjuvant
Mild-to-moderate COVID-19 adjuvant: in mild-to-moderate COVID-19 outpatients, 500 mg/day Quercetin Phytosome® plus standard care produced faster viral clearance (34 of 50 tested negative for SARS-CoV-2 after one week versus 12 of 50 on standard care alone), milder symptoms, and improvement in the inflammatory biomarker LDH.
Antioxidant and Anti-Inflammatory Action
Antioxidant and anti-inflammatory action: quercetin is among the most potent dietary flavonoids for free-radical scavenging and inhibits the NF-κB pathway that drives chronic inflammatory cytokine production. With Quercefit® delivering far more quercetin to the bloodstream, these properties translate into measurable in vivo effects — reduced oxidative stress markers, lower LDH, and reduced wheal/flare response to intradermal histamine challenge.
Mast Cell Stabilization and Histamine Modulation
Mast cell stabilization and histamine modulation: quercetin stabilizes mast cells, reducing the degranulation and histamine release that drive allergic responses. A standardized intradermal histamine challenge in healthy subjects showed Quercefit® dose-dependently reduced the wheal-and-flare skin reaction at 250 and 500 mg/day, bridging the in vitro mast cell evidence to the symptomatic benefits in rhinitis and asthma.
Confirmed Drug-Interaction Safety Profile
Confirmed drug-interaction safety profile: a dedicated non-interference assessment found Quercefit® did not appear to alter the activity of the antiplatelet agents acetylsalicylic acid, ticlopidine, or clopidogrel, did not affect stable subjects on warfarin or dabigatran, and did not interfere with glucose control. Unusual in the polyphenol space — most quercetin sources lack this kind of direct interaction screening.
Mechanism of action
Phytosome® Bioavailability Enhancement
Quercetin's near-zero oral absorption is driven by its extremely poor water solubility. Complexing quercetin 1:1 with sunflower-derived phosphatidylcholine forms a lipid-soluble Phytosome that crosses the intestinal mucosa much more efficiently. The published pharmacokinetic trial demonstrated up to 20× higher plasma quercetin AUC versus the same dose of unformulated quercetin, with dose linearity confirmed at two dose levels.
Mast Cell Stabilization
Quercetin inhibits IgE-triggered degranulation of mast cells, reducing the release of histamine, leukotrienes, and other mediators responsible for itching, sneezing, nasal discharge, and bronchoconstriction. Human evidence comes from the dose-dependent reduction in histamine-induced wheal-and-flare response observed at 250 and 500 mg/day Quercefit® in healthy volunteers.
NF-κB Pathway Inhibition
NF-κB is the master transcription factor driving production of pro-inflammatory cytokines including TNF-α, IL-6, and IL-1β. Quercetin inhibits NF-κB nuclear translocation and downstream cytokine production, providing a mechanism for the systemic anti-inflammatory effects observed across the allergy, COVID-19, and exercise recovery trials — including the LDH reductions reported in the COVID-19 adjuvant trial.
Antioxidant / Free Radical Scavenging
Quercetin's catechol B-ring and 3-hydroxyl group make it one of the more chemically active flavonoid antioxidants, directly neutralizing reactive oxygen species and regenerating other antioxidants like vitamin C and glutathione. Quercefit® supplementation balanced oxidative stress markers in the triathlon athlete trial, consistent with the in vitro free-radical scavenging activity scaling to the bloodstream when bioavailability is enhanced.
Histamine H1 Receptor Antagonism (Modest)
Quercetin shows modest binding affinity at H1 histamine receptors in vitro, adding to its anti-allergic profile beyond mast cell stabilization. The clinical effect is unlikely to approach pharmaceutical antihistamines, but contributes to the multi-mechanism profile that may explain symptomatic improvements observed in allergic rhinitis trials.
Antiviral Activity (In Vitro and Emerging Clinical)
Quercetin shows in vitro activity against multiple viral targets including SARS-CoV-2 main protease (Mpro) and ACE2 binding interference. The COVID-19 adjuvant trials in 100 mild-to-moderate outpatients showed faster viral clearance — 34/50 vs 12/50 testing negative at one week — suggesting the in vitro antiviral activity translates clinically when bioavailability is enhanced via Phytosome® delivery.
Clinical trials
Single-dose pharmacokinetic crossover clinical trial published in European Journal of Drug Metabolism and Pharmacokinetics. Compared Quercetin Phytosome® (Quercefit®, batch 06/16/PA) film-coated tablets delivering 500 mg quercetin equivalent vs unformulated quercetin at the same dose in healthy human volunteers.
Healthy adult volunteers in pharmacokinetic crossover protocol.
Quercetin Phytosome® demonstrated up to 20-fold higher oral bioavailability than unformulated quercetin. Dose linearity was confirmed at two dose levels. Foundational trial establishing the Phytosome® delivery rationale and supporting all subsequent Quercefit® dosing decisions in the 250-1,000 mg/day range.
Pilot registry-style controlled clinical trial published in Minerva Medica. 30-day intervention comparing Quercefit® 1-2 tablets/day (250-500 mg) plus standard management vs standard management alone, with outcomes assessed via the GINA classification system.
58 patients with mild-to-moderate asthma and concurrent allergic rhinitis.
Quercefit® reduced daytime symptom frequency by up to 50% and nighttime symptoms by up to 70% vs standard management alone. Decreased use of inhalers, nasal drops, and rescue medication. Improved rhinitis score and reduced oxidative stress markers. Largest published clinical signal for Quercefit® in respiratory/allergic indications.
Controlled clinical trial published in Minerva Medica. Two months of supplementation with Quercefit® 250 mg twice daily (500 mg/day total) versus control during training for sprint-format triathlon competition.
48 non-professional triathlon athletes training for sprint-format competition.
Quercefit® group ran 11.3% faster from start to finish vs 3.9% improvement in controls. Significant reductions in post-exercise muscle discomfort, cramps, and recovery time. Oxidative stress markers shifted favorably. One of the more rigorous controlled ergogenic datasets for any quercetin formulation.
Prospective, randomized, controlled, open-label clinical trial published in International Journal of General Medicine. Two-week intervention with Quercetin Phytosome® 500 mg/day plus standard care vs standard care plus placebo.
100 outpatients with mild-to-moderate COVID-19 (50 per arm).
34 of 50 patients in the Quercefit® group tested negative for SARS-CoV-2 after one week vs 12 of 50 in the placebo group. Quercetin group showed milder symptoms and significant improvement in serum LDH inflammatory biomarker. Follow-up confirmatory trial published in Frontiers in Pharmacology replicated the faster viral clearance and milder symptom signals.
Randomized controlled clinical trial published in European Review for Medical and Pharmacological Sciences. 4-week intervention with a Quercefit®-containing supplement vs placebo, assessing both seasonal and year-round allergy symptoms plus quality of life.
66 Japanese adults with seasonal and/or perennial allergic symptoms.
Repeated oral Quercefit® reduced eye itching, sneezing, nasal discharge, and sleep disturbance for both seasonal and annual allergens vs placebo. Improved quality of life scores. Confirms the rhinitis findings from the Cesarone et al. pilot registry in a different ethnic population with rigorous placebo control.
Pilot non-interference clinical trial published in Esperienze Dermatologiche. Evaluated potential interactions of Quercefit® with the antiplatelet agents acetylsalicylic acid, ticlopidine, and clopidogrel; anticoagulants warfarin and dabigatran; and glucose control in stable subjects.
Stable adult subjects on antiplatelet, anticoagulant, or glucose-control medications.
Quercefit® did not appear to alter the activity of any of the antiplatelet agents tested, had no impact on stable subjects using warfarin or dabigatran, and did not interfere with glycemic control. Notable for filling a safety gap — most quercetin sources lack direct interaction screening with high-concern medications.