Quercetin: more than a powerful antioxidant.
Quercetin (from the Latin quercus = oak) is a natural yellow pigment found in many plants. It is the most quantitatively significant representative of all flavonoids and is widely distributed throughout the plant kingdom. Quercetin is found in apples, onions, berries, tea, brassicas, nuts, flowers, leaves, bark, various plant seeds, and also in the skin of grapes, and ultimately in wine. It is also found in countless medicinal plants such as ginkgo biloba, St. John’s wort (Hypericum perforatum), and elderberry (Sambucus canadensis). In these cases, a significant portion of the healing effects is even attributed to quercetin. According to various scientific and experimental studies, it has a wide range of effects on humans.
Quercetin is an antioxidant flavonoid that has been used for over 30 years to increase resistance to food and respiratory allergies. Its biological effects are primarily due to its antioxidant activity, its specific synergy with vitamin C (quercetin and vitamin C mutually protect and regenerate each other), and its diverse and versatile anti-inflammatory activity:
- Quercetin inhibits the enzymes cyclooxygenase (COX) and lipooxygenase (LOX), which reduces the production of the main inflammatory mediators: prostaglandins and leukotrienes.
- Quercetin inhibits histamine production by stabilizing basophils and mastocytes. Histamine is directly responsible for most of the unpleasant symptoms associated with allergies (sneezing, itching, etc.).
- Quercetin acts directly in the intestinal tract to reduce reactions to food allergens.
- A longitudinal study of 809 men over a five-year period (Lancet, October 23, 1993; 342: 1007-11) shows that increased consumption of quercetin reduces overall cardiovascular risk by one-third. Quercetin has scientifically proven antithrombotic and vasodilatory effects.
- The risk of stroke is inversely proportional to the intake of quercetin: those who consume the least have a four-fold higher risk.
- Quercetin protects the kidneys from the proven toxicity of certain medications (cyclosporine).
- Quercetin significantly improves the symptoms of prostatitis and chronic pelvic pain syndrome.
- Quercetin’s anti-cancer activity has been the subject of several promising studies.
Quercetin’s health benefits have long been limited due to its mediocre intestinal absorption, requiring the daily intake of large numbers of capsules to achieve its benefits. An improved form of quercetin, isoquercitrin (quercetin-3-0-glucoside), has recently been isolated from the Brazilian plant Dimorphandra mollis, and thanks to the glucoside portion of the molecule, its proven gastrointestinal absorption is now 5 to 20 times better. Peak plasma concentrations are also reached six times faster than with traditional forms of quercetin.
Quercetin and rutoside are among the most potent antioxidants in the polyphenol group, along with anthocyanins, proanthocyanidins, and epigallocatechin gallate (green tea).