title: Comparison of the Antioxidant Effects of Quercitrin and Isoquercitrin: Understanding the Role of the 6″-OH Group.
abstract: The role of the 6″-OH (ω-OH) group in the antioxidant activity of flavonoid glycosides has been largely overlooked. Herein, we selected quercitrin (quercetin-3-O-rhamnoside) and isoquercitrin (quercetin-3-O-glucoside) as model compounds to investigate the role of the 6″-OH group in several antioxidant pathways, including Fe2+-binding, hydrogen-donating (H-donating), and electron-transfer (ET). The results revealed that quercitrin and isoquercitrin both exhibited dose-dependent antioxidant activities. However, isoquercitrin showed higher levels of activity than quercitrin in the Fe2+-binding, ET-based ferric ion reducing antioxidant power, and multi-pathways-based superoxide anion-scavenging assays. In contrast, quercitrin exhibited greater activity than isoquercitrin in an H-donating-based 1,1-diphenyl-2-picrylhydrazyl radical-scavenging assay. Finally, in a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl assay based on an oxidatively damaged mesenchymal stem cell (MSC) model, isoquercitrin performed more effectively as a cytoprotector than quercitrin. Based on these results, we concluded that (1) quercitrin and isoquercitrin can both indirectly (i.e., Fe2+-chelating or Fe2+-binding) and directly participate in the scavenging of reactive oxygen species (ROS) to protect MSCs against ROS-induced oxidative damage; (2) the 6″-OH group in isoquercitrin enhanced its ET and Fe2+-chelating abilities and lowered its H-donating abilities via steric hindrance or H-bonding compared with quercitrin; and (3) isoquercitrin exhibited higher ROS scavenging activity than quercitrin, allowing it to improve protect MSCs against ROS-induced oxidative damage.
authors.affiliation: School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou Higher Education Mega Center, Guangzhou 510006, China. lixc@gzucm.edu.cn.
authors.forename: Xican
authors.initials: X
authors.lastname: Li
authors.affiliation: School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou Higher Education Mega Center, Guangzhou 510006, China. Jiangqiande920711@163.com.
authors.forename: Qian
authors.initials: Q
authors.lastname: Jiang
authors.affiliation: School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou Higher Education Mega Center, Guangzhou 510006, China. wtttx0304@163.com.
authors.forename: Tingting
authors.initials: T
authors.lastname: Wang
authors.affiliation: School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou Higher Education Mega Center, Guangzhou 510006, China. 15622829151@163.com.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Liu
authors.affiliation: School of Basic Medical Science, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou Higher Education Mega Center, Guangzhou 510006, China. lixican@126.com.
authors.forename: Dongfeng
authors.initials: D
authors.lastname: Chen
keywords: 6″-OH; Q3G; antioxidant mechanisms; flavonoid glycoside; isoquercitrin; mesenchymal stem cells; quercitrin; ω-OH