quercetin

Quercetin is a naturally occurring plant pigment (flavonoid) found in many fruits and vegetables such as onions, apples, berries, and green tea. It is widely available as a dietary supplement. Quercetin exhibits antioxidant and anti-inflammatory properties by scavenging free radicals and stabilizing cells that release histamine[2][3][5]. Its mechanisms of action include inhibition of histamine release (antihistamine effect), modulation of the mechanistic target of rapamycin (mTOR) pathway through activation of AMP-activated protein kinase (AMPK), induction of autophagy via mTORC1 inhibition and TFEB nuclear translocation[6], as well as influencing multiple cell death pathways including apoptosis and necroptosis[6]. Quercetin has been studied for potential benefits in cardiovascular disease prevention (antihypertensive effects), cancer chemoprevention or adjunctive therapy in chemotherapy regimens[2][3], allergy symptom relief due to its antihistaminic activity[1][3], neuroprotection in Parkinson’s disease models[1], diabetes management through effects on glucose metabolism[8], and other inflammatory conditions. However, most clinical evidence remains limited or inconclusive; much research has been conducted in vitro or in animal models rather than large-scale human trials.

Other names

pentahydroxyflavonequercetinevitamin P