[Chemical constituents of Hypericum stellatum and their antioxidant bioactivities]

Hypericum stellatum is an important ethnomedicinal plant endemic to southwest China. Ultra high performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was applied to analyze the chemical constituents of H. stellatum. Seventeen compounds from H. stellatum were tentatively identified using UPLC-Q-TOF-MS data. Antioxidant activity and total phenolic content were investigated by DPPH assay and Folin-Ciocalted methods. The EtOAc extract with high total phenolic content showed prominent antioxidant activity. The EtOAc extract of H. stellatum was separated and purified by column chromatography, including silica gel, Sephedex LH-20, and RP-HPLC. The isolates were defined by 1D, 2D NMR data. As a result, ten compounds were isolated and assigned as quercetin (Ⅰ), quercetin 3-O-β-D-glucopyranoside (Ⅱ), 1,3,6,7-tetrahydroxylxanthone (Ⅲ), 1,3,5,6-tetrahydroxyxanthone (Ⅳ), 1,3,7-trihydroxyxanthone (Ⅴ), 3, 6, 7-trihydroxy-1-methoxyxanthone (Ⅵ), calycinoxanthon D (Ⅶ), caffeic acid ethyl ester (Ⅷ), chlorogenic acid (Ⅸ) and chlorogenic acid ethyl ester (Ⅹ). This is the first report on chemical constituents and bioactivity of H. stellatum. The antioxidant activity of chemical constituents was tentatively found, which provided a foundation for further researches on the genus Hypericum and the traditional uses of H. stellatum.