A importância da Quercitina para a saude respiratória
03 Nov

Quercetin is another member of the polyphenol family. Considered a flavonoid type of polyphenol, quercetin is found in many fruits and vegetables, including onions, apples, cherries, broccoli, tomatoes and berries, as well as green tea.

We look for quercetin most of the time seasonally as a remedy for people with allergic afflictions. [1] Quercetin neutralizes the allergic response by suppressing the formation of antigen-specific immunoglobulin (Ig) E antibodies, thus acting at a very early stage in the allergic response. [2], [3] In addition, quercetin inhibits the release of histamine and pro-inflammatory substances involved in allergic reactions. [4] By these and other mechanisms, quercetin can improve contact dermatitis and photosensitivity, [5] allergic rhinitis [6] and asthma. [7], [8]

In addition to these antiallergic effects, quercetin can help balance the immune response by decreasing the production of cytokines related to the allergic response [9] [10], [11], [12], [13]

Quercetin also shows an affinity for the respiratory tract in the protection it offers against oxidative damage and inflammation associated with exposure to particles.

Studies have demonstrated several mechanisms by which quercetin and other flavonoids can reduce the infectivity of a wide variety of respiratory and other viruses, [14] including influenza, adenovirus, rhinovirus and coronavirus. [15], [16], [17], [18] Quercetin also shows affinity for the respiratory tract in the protection it offers against oxidative damage and inflammation associated with exposure to particles. [19] Quercetin can be found in very high levels in St. John's wort (Hypericum perforatum), [20] and may be one of the constituents that contributes to its antiviral and mood-stabilizing effects. [21], [22], [23]], [24], [25]

Quercetin helps to protect the body against reactive oxygen species, although studies show that it can also have pro-oxidant effects. [26], [27], [28] Although we think of pro-oxidants negatively, they are activators of our body's endogenous antioxidant. and transcription of the protective detoxification enzyme activating the Nrf2 / ARE pathway. In animals, quercetin supplementation has been observed to increase levels of alpha-tocopherol (a form of vitamin E) while decreasing lipid peroxidation markers; however, varying effects on glutathione levels have been shown. [29], [30] Providing additional antioxidants along with quercetin, such as vitamin C and glutathione, can help to counteract the pro-oxidant effects and increase quercetin recycling. [14], [31] In fact, vitamin C appears to increase the activity of quercetin, in part by stabilizing the quercetin molecule itself. [32]

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