Isolation and Identification of the Anti-Oxidant Constituents from Loropetalum chinense (R. Brown) Oliv. Based on UHPLC–Q-TOF-MS/MS

The aim of this study was to identify the chemical constituents of Loropetalum chinense (R. Brown) Oliv. (LCO) and determine which of these had antioxidant effects. The chemical composition of a 70% ethanol extract of LCO was analyzed systematically using UHPLC–Q-TOF-MS/MS. The chemical components of the 70% ethanol extract of LCO were then separated and purified using macroporous resin and chromatographic techniques. Antioxidant activity was evaluated using a DPPH assay. In total, 100 compounds were identified tentatively, including 42 gallic acid tannins, 49 flavones, and 9 phenolic compounds. Of these, 7 gallium gallate, 4 flavonoid and 8 quinic acid compounds were separated and purified from the 70% ethanol extract of LCO. The compounds identified for the first time in LCO and in the genus Loropetalum were 3,4,5-trimethoxyphenyl-(6′-O-galloyl)-O-β-d-glucopyranoside, protocatechuic acid, ethyl gallate, 5-O-caffeoylquinic acid, 3-O-caffeoylquinic acid, 3,5-O-diocaffeoylquinic acid, 4,5-O-diocaffeoylquinic acid and 3,4-O-diocaffeoylquinic acid. The 50% inhibitory concentration (IC(50)) values of compounds 1,2,3,4,6-penta-O-galloyl-β-d-glucose, gallic acid, protocatechuic acid, and ethyl gallate were 1.88, 1.05, 1.18, and 1.05 μg/mL, respectively. Compared with the control group (V(C)) (2.08 μg/mL), these compounds exhibited stronger anti-oxidation activity. This study offered considerable insight into the chemical composition of LCO, with preliminary identification of the antioxidant ingredients.