Quercetin

Quercetin is a flavonoid polyphenol found abundantly in onions, capers, apples, and many other plant foods. It has been studied for decades as an antioxidant and anti-inflammatory compound, and more recently has attracted significant research attention as part of the most studied senolytic combination in humans: dasatinib plus quercetin (D+Q).

Senolytic Activity {#senolytic-activity}

Senolytics are compounds that selectively eliminate senescent cells , cells that have permanently stopped dividing but resist programmed cell death. These “zombie cells” accumulate with age and secrete a damaging mixture of inflammatory cytokines, proteases, and growth factors known as the senescence-associated secretory phenotype (SASP). SASP factors degrade surrounding tissue, promote chronic inflammation, and drive age-related dysfunction across multiple organ systems.

Quercetin acts as a senolytic by inhibiting the BCL-2 and BCL-xL pro-survival proteins that allow senescent cells to evade apoptosis. Dasatinib, a tyrosine kinase inhibitor originally developed as a cancer drug, complements quercetin by targeting separate survival pathways in senescent cells. Together, D+Q depletes senescent cell burden more effectively than either agent alone.

The first-in-human D+Q trial (PMID 31542391, Mayo Clinic 2019) enrolled 14 patients with diabetic kidney disease. Three days of D+Q treatment produced significant reductions in senescent cell markers (p16, p21) and multiple SASP factors in adipose tissue and skin. This small study established proof-of-concept that the senolytic protocol can reduce cellular senescence burden in living humans.

The STAMINA pilot study (Lancet EBioMedicine 2025) enrolled 12 older adults with slow gait speed and mild cognitive impairment , two hallmarks of senescent cell accumulation in neural and musculoskeletal tissues. Participants received 100 mg dasatinib plus 1250 mg quercetin on two consecutive days every two weeks for six cycles. The study demonstrated feasibility and preliminary safety signals for this intermittent protocol in a frail older population.

Important caveats: The senolytic benefit of quercetin is specific to the D+Q combination and the “hit-and-run” intermittent high-dose protocol , not daily low-dose supplementation. Dasatinib is a prescription chemotherapy drug with a meaningful side-effect profile and is not available for routine self-supplementation. All human trials to date are small and early-phase, establishing safety and feasibility rather than confirmed efficacy. The senolytic use of quercetin remains an area of active investigation rather than established clinical practice.

Antioxidant and Anti-inflammatory Effects {#antioxidant-anti-inflammatory}

Independent of its senolytic application, quercetin is one of the most studied plant polyphenols for its antioxidant and anti-inflammatory properties. In vitro studies demonstrate that quercetin scavenges reactive oxygen species, chelates metal ions, and inhibits lipid peroxidation. In animal models, quercetin reduces markers of systemic inflammation including NF-kB signaling, TNF-alpha, and interleukin-6.

Human evidence is more limited but exists. Flavonoid-rich diets are consistently associated with lower inflammatory biomarkers in epidemiological studies, though isolating quercetin’s contribution from other dietary polyphenols is methodologically difficult. Some short-term supplementation trials show modest reductions in C-reactive protein and other inflammatory markers in healthy adults and in individuals with metabolic conditions, though effect sizes are small and results are not fully consistent across studies.

Quercetin’s flavonoid structure allows it to modulate multiple intracellular signaling pathways including MAPK, PI3K/Akt, and NF-kB , mechanisms shared with other plant polyphenols that collectively contribute to the well-established anti-inflammatory effects of plant-rich diets.

Cardiovascular Support {#cardiovascular-support}

Several meta-analyses have examined quercetin’s effect on blood pressure. A frequently cited analysis of randomized controlled trials found statistically significant reductions in systolic blood pressure with quercetin supplementation, with effects more pronounced at doses above 500 mg/day and in individuals with hypertension or metabolic syndrome at baseline. Effect sizes are modest , typically in the range of 3–5 mmHg systolic , and are not uniformly replicated across all trials.

Mechanistically, quercetin may support vascular function through endothelial nitric oxide bioavailability, inhibition of angiotensin-converting enzyme, and direct vasodilatory effects. A 2025 study in GeroScience found that D+Q affects chromatin structure in both young and senescent vascular smooth muscle cells, suggesting effects on vascular biology that extend beyond blood pressure alone.

Bioavailability and Dosing

Quercetin from food and standard supplements is poorly absorbed , oral bioavailability is typically below 10% due to rapid metabolism and limited intestinal uptake. Quercetin phytosome, a formulation combining quercetin with sunflower phospholipids, improves absorption approximately 20-fold compared to unformulated quercetin and is the form used in most recent human research.

For general antioxidant and cardiovascular applications, typical supplement doses range from 250–1000 mg/day of quercetin phytosome. The senolytic D+Q protocol used in clinical research uses 1000–1250 mg quercetin in short intermittent bursts (2–3 consecutive days every 2–4 weeks), always in combination with prescription dasatinib and under medical supervision.