Ideal ingredient calling card: Quercetin

Ideal ingredient calling card: Quercetin

This naturally-occurring flavonoid can be found in many organic substances from the bark of black oak to apples and onions.



- Quercetin is a naturally-occurring glycosidic flavonol (a member of the flavonoid family of compounds) that has a long history of consumption as part of the normal human diet

- The name “quercetin,” used since 1857, is derived from quercetum (oak); quercetin was a yellow crystalline pigment extracted from the inner bark of black oak to dye wool



- Ubiquitously abundant as glycosidic flavonoids in leaves, grains, fruits and vegetables, particularly apples and onions

- Cranberries and black and green tea (Camellia sinensis) are particularly rich in quercetin (about 2,000–2,500 mg/kg)

- Commercially manufactured by extraction of the quercetin glycoside from fava beans, Uncaria leaves, apples and onions



- Not approved as a specific therapeutic for any condition; better positioned to provide long-term rather than short-term health benefits

- Used as an ingredient in supplements, beverages and foods

- Potent antioxidant; scavenges reactive oxygen and singlet oxygen speciesin addition to radicals of different origins

- Alleviates bruising, varicose veins, and improves fragile capillaries (functionalities important in cosmetics)

- Inhibits growth of malignant cells by arresting the cell cycle in the late-G1-phase or inducing apoptosis

- Antiviral activity stems from its ability to bind with viral proteins and prevent the viral nucleic acid synthesis



+ Various benefits to human health have propelled the addition of quercetin to various traditional food products

+ An ingredient in beverages, pasta, energy drinks, fruit juices, and soft candies at ~500 mg quercetin/serving

- Very bitter and astringent; masking requires expert assistance from flavor chemistry

+ A yellow crystalline solid with a shelf life of 2 years at ambient temperature

+ A water soluble form added to high added-value foods, beverages, and supplements for enhanced performance

+ Popular in anti-aging skin preparations for anti-inflammatory application

+ Often packaged with bromelain (enzyme from pineapple) because both are anti-inflammatories



- Interest from sports and athlete communities for mental and physical performance enhancement benefits

- Growing body of science about the anti-inflammatory effects of quercetin

- Quercetin protects against Metabolic Syndrome X and build-up of abdominal fat



Strong evidence

- Helps prevents oxidative stress associated diseases: cancer, cardiovascular diseases, inflammation, and other degenerative diseases

- Intestinal microflora splits the beta-glycosidic bond between glycoside and aglycone and facilitates absorption

- Scavenges reactive oxygen species and chelates metal ions and acts like an antihistamine

- Quercetin-rich diet significantly lowers the risk of mortality from coronary heart disease and stroke

- Inhibits 15-lipoxygenase, an enzyme that catalyzes oxidative modification of low-density lipoprotein associated with atherosclerosis

- Quercetin benefits depend on bioavailability and uptake by the circulatory system


SURPRISING FACT: Quercetin itself (aglycone quercetin), as opposed to quercetin glycosides, is not a normal dietary component.

RESOURCE: Harwood et. al., A critical review of the data related to the safety of quercetin and lack of evidence of in vivo toxicity, including lack of genotoxic/carcinogenic properties. Food and Chemical Toxicology, Volume: 45, Issue: 11, Pages: 2179-2205.

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