Antioxidant Activities of Quercetin and Its Complexes for Medicinal Application

Dong Xu, Meng-Jiao Hu, Yan-Qiu Wang and Yuan-Lu Cui *

Research Center of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin 300193, China; dongxu418@163.com (D.X.); humengjiao0626@163.com (M.-J.H.);
yqwang1994@163.com (Y.-Q.W.)
* Correspondence: cuiyl@tju.edu.cn; Tel.: +86-22-59596170; Fax: +86-22-59596170

Received: 6 March 2019; Accepted: 19 March 2019; Published: 21 March 2019

Abstract
Quercetin is a bioactive compound that is widely used in botanical medicine and traditional Chinese medicine due to its potent antioxidant activity. In recent years, antioxidant activities of quercetin have been studied extensively, including its effects on glutathione (GSH), enzymatic activity, signal transduction pathways, and reactive oxygen species (ROS) caused by environmental and toxicological factors. Chemical studies on quercetin have mainly focused on the antioxidant activity of its metal ion complexes and complex ions. In this review, we highlight the recent advances in the antioxidant activities, chemical research, and medicinal application of quercetin.

Keywords
quercetin; polyphenol; antioxidant activity; oxidative stress; complex