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

Abstract

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 (IC50) 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 (VC) (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.

Keywords

• Loropetalum chinense (R. Brown) Oliv.
• antioxidant constituents
• isolation
• identification
• UHPLC-Q-TOF-MS/MS