Quercitrin (Quercetin 3-rhamnoside)

Quercitrin (quercetin 3-rhamnoside) is a flavonoid glycoside in which quercetin is bound to the sugar rhamnose, altering its solubility and metabolic profile compared to free quercetin. It exerts antioxidant, anti-inflammatory, and antiviral effects primarily by inhibiting pro-inflammatory enzymes such as COX-2 and lipoxygenase, and by scavenging reactive oxygen species.

Origin & History

Quercitrin (quercetin 3-rhamnoside) is a flavonol glycoside naturally occurring in fruits, vegetables, and herbs including onions, apples, berries, and tea leaves, where it serves as a secondary metabolite for pigmentation and oxidative stress defense. Commercial extraction typically involves solvent-based methods using ethanol or methanol from plant sources, followed by chromatographic purification or crystallization.

Historical & Cultural Context

While no direct traditional use of quercitrin was documented in the research, quercetin-related compounds appear in Traditional Chinese Medicine formulas such as Bushen Yiqi Lixue Yangtai (BYLY) for recurrent spontaneous abortion. Quercitrin was identified as a potential key component among 132 active compounds in this traditional remedy.

Health Benefits

• May reduce upper respiratory tract infection severity by 36% and sick days by 31% in fit adults over 40 (based on quercetin studies, moderate evidence) • Potential antiviral activity shown in COVID-19 patients with faster viral clearance (76% vs 9.5% negative after 1 week, preliminary evidence) • May help prevent oral mucositis in chemotherapy patients (30% vs 60% incidence, preliminary evidence) • Anti-inflammatory effects demonstrated through reductions in CRP, D-dimer, and ferritin markers (preliminary evidence) • Well-tolerated at doses up to 2000 mg/day with no severe adverse events in COPD patients (moderate evidence)

How It Works

Quercitrin inhibits cyclooxygenase-2 (COX-2) and 5-lipoxygenase, suppressing prostaglandin E2 and leukotriene B4 synthesis to reduce inflammatory signaling. It also downregulates NF-κB pathway activation, limiting transcription of pro-inflammatory cytokines including TNF-α and IL-6. Additionally, quercitrin chelates transition metal ions involved in Fenton reactions, reducing hydroxyl radical formation and oxidative cellular damage.

Scientific Research

While no quercitrin-specific human trials were identified, multiple RCTs have studied quercetin (the active form released from quercitrin). Key trials include a URTI prevention study in 1002 subjects (PMID: 20478383), a COVID-19 outpatient trial with 42 participants (PMID: 36712674), and safety studies in COPD patients testing doses up to 2000 mg/day (PMID: 32071149).

Clinical Summary

Most clinical evidence for quercitrin comes from trials using quercetin broadly, as quercitrin is a quercetin glycoside that undergoes partial conversion to quercetin aglycone after intestinal metabolism. A randomized controlled trial in physically fit adults over 40 found quercetin supplementation reduced upper respiratory tract infection severity by approximately 36% and sick days by 31%, though sample sizes were modest. Preliminary clinical data from a COVID-19 study reported viral clearance in 76% of quercetin-supplemented patients versus 9.5% of controls after one week, but this was a small, early-phase study requiring replication. Overall, evidence is promising but largely moderate-quality, with larger controlled trials needed specifically examining quercitrin's distinct bioavailability profile.

Nutritional Profile

Quercitrin (Quercetin 3-rhamnoside) is a flavonoid glycoside with molecular formula C21H20O11 and molecular weight of 448.38 g/mol. It is not a macronutrient source and contributes negligible caloric value. As a bioactive compound, it consists structurally of the flavonol aglycone quercetin bound to the sugar rhamnose (6-deoxy-L-mannose) at the 3-position. Typical concentrations in plant sources: found at 0.1–2.5 mg/g dry weight in buckwheat leaves, 0.5–3.0 mg/g in citrus peel (particularly lemon and lime), 0.2–1.8 mg/g in Rhus coriaria (sumac), and trace amounts (0.05–0.3 mg/g) in black tea and red wine. Bioavailability is notably lower than free quercetin aglycone due to the rhamnose moiety; intestinal absorption requires rhamnosidase enzyme activity primarily from colonic microbiota, resulting in delayed but sustained quercetin release in the large intestine. Estimated oral bioavailability is approximately 20–30% relative to quercetin aglycone. Once deglycosylated, quercetin undergoes hepatic methylation and sulfation, producing isorhamnetin and quercetin sulfates as primary circulating metabolites. No significant vitamin, mineral, fiber, or protein content is associated with purified quercitrin itself. Antioxidant capacity measured at approximately 2.5–3.0 mmol Trolox equivalents per gram (FRAP assay), slightly lower than free quercetin (~4.7 mmol TE/g) due to glycosylation reducing free radical scavenging at the 3-OH position.

Preparation & Dosage

Clinical studies of quercetin (released from quercitrin) used 500-1000 mg/day for 10-12 weeks for general health, up to 2000 mg/day for COPD patients, with powder or capsule forms being most common. No standardization specific to quercitrin content was detailed in trials. Consult a healthcare provider before starting any new supplement.

Synergy & Pairings

Vitamin C, Zinc, Vitamin D3, Bromelain, Green Tea Extract

Safety & Interactions

Quercitrin is generally well tolerated at typical dietary and supplemental doses, with mild gastrointestinal discomfort (bloating, nausea) reported occasionally at higher doses above 500 mg/day quercetin equivalents. It may inhibit CYP3A4 and P-glycoprotein, potentially raising plasma concentrations of drugs such as cyclosporine, statins, and certain anticoagulants like warfarin, necessitating caution. Quercitrin may also potentiate the effects of antiplatelet agents due to inhibition of thromboxane A2 synthesis, increasing bleeding risk when combined with aspirin or clopidogrel. Safety data in pregnancy and lactation are insufficient, and use during these periods is not recommended without medical supervision.