Apple (quercetin
Description
Flavonol polyphenol ubiquitous in plant kingdom (onion skin, apple peel, blueberry, capers, green tea). Mechanisms: direct free-radical scavenging (hydroxyl, superoxide, peroxyl, alkoxyl); chelation of pro-oxidant metal cations (Cu2+, Fe2+) blocking Fenton reactions; inhibition of collagenase, elastase, and hyaluronidase preserving ECM structural integrity; anti-inflammatory via 5-LOX, COX-2, and NF-kB pathway inhibition; upregulation of endogenous antioxidant enzymes. Anti-aging, antioxidant, and anti-inflammatory active. Poor water solubility (~0.01 mg/mL) limits aqueous formulation; encapsulation (liposomes, cyclodextrins, nanoemulsions) required for effective delivery.
Function
Properties
Regulatory Status
Quercetin (CAS 117-39-5) is permitted in EU cosmetics under Regulation (EC) No 1223/2009 without specific concentration limits, and is approved for cosmetic use in the US with no pre-market authorization required. Dermal absorption into the stratum corneum is approximately 18%, with limited systemic exposure due to extensive first-pass metabolism. In vitro mutagenicity signals are not expressed in vivo; renal adenomas observed in male rats at high oral doses are considered species-specific and not relevant to topical human use.
GRAS status granted 2010 for QU995 formulation (food use). Permitted as cosmetic ingredient with no pre-market approval required. Not GRASE-classified for OTC sunscreen use. FDA withdrew drug approval for quercetin-containing drugs in 1970 due to insufficient efficacy evidence.
Ratings
Identifiers
No registry identifiers available for this ingredient.