Flavonoid-Rich Fraction from Sageretia theezans Leaves Scavenges Reactive Oxygen Radical Species and Increases the Resistance of Low-Density Lipoprotein to Oxidation

Abstract

To explore their bioactive fractions, Sageretia theezans leaves were extracted with 60% acetone and then fractionated sequentially with hexane, ethyl acetate, and water. Reactive oxygen radical species (ROS) (HOCl, ONOO⁻, and O₂ ^·−) scavenging activity, oxygen radical absorbance capacity (ORAC) value, and total phenolic content of each fraction were investigated. The ethyl acetate fraction had the largest total phenolic content and ORAC value and displayed the strongest ROS scavenging activity. The ethyl acetate fraction at 2 μmol of gallic acid equivalents/L prolonged the lag time of low-density lipoprotein oxidation by 260% compared to the control. In the ethyl acetate fraction, 7-O-methylmearnsetin 3-O-rhamnoside and the other nine flavonols were characterized using high-performance liquid chromatography with electrochemical detection. The total flavonoid content in the ethyl acetate fraction was 460 mg/g. 7-O-Methylmyricetin 3-O-rhamnoside and 7-O-methylmearnsetin 3-O-rhamnoside were the predominant flavonoids, making up 36% and 17% of the total flavonoid content, respectively.