Quercetin refers to a water soluble bioflavonoid found in fruits, vegetables, and grains. Highest levels are found in onions and apples. Just like other elements in the bioflavonoid family, quercetin has anti-oxidant, pain management and regulation of appropriate cell growth. It therefore has role in modulating and regulating inflammatory processes in the body as well as immune supporting activity.
Being a flavonoid, quercetin scavenges for free radicals that harm the body cells by causing cell membrane damage, tampering with DNA and ultimately resulting in cell death. According to Researchers from the Linus Pauling Institute at the University of Oregon , the antioxidant potency of a flavonoid is dependent upon its molecular structure. Quercetin having all the necessary structural features makes it one of the most powerful antioxidants. Besides, antioxidants fix damaged molecules by inhibiting metal radical production that provides a “shield effect”. Also, stimulates gene expression and the production of more endogenous antioxidants.
Quercetin provides an immune supporting activity by acting mainly on leucocytes and targeting the various intracellular signaling kinases, phosphatases and membrane proteins that ate often crucial for specific cellular functions. Quercetin counteracts inflammation and minimizes hypersensitivity due to its ability to stabilize histamine releasing cells. Histamine stabilization occurs due to quercetin’s ability to prevent the histamines to attach to and irritate the body cells. These counteract allergic reactions by the body such as sneezing or itching. Additionally, laboratory studies have also shown that quercetin counteracts the effects of IgE mediated reactions.
Quercetin also, inhibits the production of enzymes such as cyclo-oxygenase(COX) and lipooxygenase(LOX). It limits LPS-induced inflammation through the inhibition of Src- and Syk-mediated phosphatidylinositol-3-Kinase(PI3K)-(p85), tyrosine phosphorylation. Besides, quercetin confers an immunosuppressive effect on dendritic cell function. It also possesses mast cell stabilizing and confers gastrointestinal cytoprotective activity.
Dietary flavonoids also reduce the hardening of vessels .According to a report by the university of Maryland Medical Center; quercetin prevents the buildup of plaques in arteries and improves endothelial function. In addition, quercetin counteracts Low Density Lipoprotein (LDL) which is the bad cholesterol. A study among overweight subjects has shown that quercetin reduced their LDL concentrations. Besides, Quercetin plays a role in the regulation of body’s blood pressure. According to a research by Advances in Nutrition Group, quercetin has the potential to lower blood pressure in individuals who are hypertensive.
Flavonoids also regulate optimal cellular growth due to its antioxidant and antimutagenic property. Several In vitro studies have shown that quercetin inhibits lipopolysaccharide (LPS) induced tumor necrosis factor alpha (TNF-alpha), macrophage production and LPS-induced Il-8 production in the lung A549 cells. A combination with vitamin c (ascorbic acid) potentiates its antimutagenic activity. The antimutagenic activity was associated with free radical scavenging activity. Ability to induce apoptosis and change the expression of the apoptotic protein also helps in counteracting unwanted multiplication of cells.
Quercetin also increases endurance and thereby improving athletic performance. As per a 2012 study by the Journal of Research in Medical Sciences, non-professional athletes, who used quercetin-vitamin C supplements coupled with regular exercise, showed a decreased oxidative stress and decreased inflammatory biomarkers.
Quercetin has the ability to inhibit unnecessary oxidation coupled with regulation of inflammatory processes that reduce swellings in body organs.. A report in the 2008 issue of the “Journal of Pre-Clinical and clinical research” (JPCCR) delineates the action of quercetin in relieving joint pain within a period of 2 to 3 days. On the other hand, the University of Maryland Medical Center in vitro studies have shown that quercetin prevents the release of histamines.
Quercetin is also available in supplement form whereby it is packaged with bromelain, a pineapple derived enzyme since both have anti-inflammatory properties. Though quercetin is available in form of dietary supplement, the American Cancer Society recommends intake through food sources because such sources contain other necessary vitamins and minerals that work augments quercetin’s activity. The dosage of quercetin ranges from 12.5 to 25 mg per kilogram body weight.