Abstract
Quercetin is the great representative of polyphenols, flavonoids subgroup, flavonols. Its main natural sources in foods are vegetables such as onions, the most studied quercetin containing foods, and broccoli; fruits (apples, berry crops, and grapes); some herbs; tea; and wine. Quercetin is known for its antioxidant activity in radical scavenging and anti-allergic properties characterized by stimulation of immune system, antiviral activity, inhibition of histamine release, decrease in pro-inflammatory cytokines, leukotrienes creation, and suppresses interleukin IL-4 production. It can improve the Th1/Th2 balance, and restrain antigen-specific IgE antibody formation. It is also effective in the inhibition of enzymes such as lipoxygenase, eosinophil and peroxidase and the suppression of inflammatory mediators. All mentioned mechanisms of action contribute to the anti-inflammatory and immunomodulating properties of quercetin that can be effectively utilized in treatment of late-phase, and late-late-phase bronchial asthma responses, allergic rhinitis and restricted peanut-induced anaphylactic reactions. Plant extract of quercetin is the main ingredient of many potential anti-allergic drugs, supplements and enriched products, which is more competent in inhibiting of IL-8 than cromolyn (anti-allergic drug disodium cromoglycate) and suppresses IL-6 and cytosolic calcium level increase.
Highlights
IntroductionThe expansion of allergic diseases has been extended during last three decades all over the world
The expansion of allergic diseases has been extended during last three decades all over the world.Different changes in environmental factors may contribute to this problem [1]
The interaction of environmental and genetic factors with the immune system can lead to the development of allergic diseases [2]
Summary
The expansion of allergic diseases has been extended during last three decades all over the world. Fruits (apples as well as berry crops, such as strawberry, red raspberry, blueberry, cranberry and black currants), green tea and wine could be considered abundant dietary sources [22,25,33,34,35,36,37]. The form distribution is nearly reversed—83.3% quercetin aglycone and 16.7% quercetin glucosides [51] In apples, another great quercetin source, there are well studied antioxidant compounds such as quercetin-3-galactoside, quercetin-3-glucoside, and quercetin-3-arabinoside [33,41] in the content range of 21–72 mg/kg; quercetin-3-rhamnoside [52]; and quercetin-3-rutinoside [28]. Glucose or glucuronic acid and galactose are the main sugars in conjugated forms of quercetin in wines [19]
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