Quercetin, Inflammation and Immunity

Abstract

In vitro and some animal models have shown that quercetin, a polyphenol derived from plants, has a wide range of biological actions including anti-carcinogenic, anti-inflammatory and antiviral activities; as well as attenuating lipid peroxidation, platelet aggregation and capillary permeability. This review focuses on the physicochemical properties, dietary sources, absorption, bioavailability and metabolism of quercetin, especially main effects of quercetin on inflammation and immune function. According to the results obtained both in vitro and in vivo, good perspectives have been opened for quercetin. Nevertheless, further studies are needed to better characterize the mechanisms of action underlying the beneficial effects of quercetin on inflammation and immunity.

Keywords: dietary sources; immune function; inflammation; metabolism; quercetin.

Figure 1

Molecular structure of quercetin, quercetin glycoside, quercetin glucuronide, quercetin sulfate and methylated quercetin.

Figure 2

Working model on how quercetin block tumor necrosis factor-α (TNFα)-mediated inflammation. Quercetin prevents TNF-α from directly activating extracellular signal-related kinase (ERK), c-Jun NH₂-terminal kinase (JNK), c-Jun, and nuclear factor-κB (NF-κB), which are potent inducers of inflammatory gene expression and protein secretion. In addition, quercetin may indirectly prevent inflammation by increasing peroxisome proliferator-activated receptor c (PPARγ) activity, thereby antagonizing NF-κB or activator protein-1(AP-1) transcriptional activation of inflammatory genes. Together, these block TNF-α-mediated induction of inflammatory cascades.