|Chen, C-y. Oliver|
Submitted to: Journal of Medicinal Food
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2009
Publication Date: 9/20/2009
Citation: Chung, S., Chen, C., Blumberg, J.B. 2009. Flavanoid-rich fraction from Sageretia theezans leaves scavenges reactive oxygen radical species and increases the resistance of low-density lipoprotein to oxidation. Journal of Medicinal Food. 12(6):1310-1315. Interpretive Summary: Sageretia theezans is a semi-evergreen spinescent, 1-3 meter tall shrub of the Rhamnaceae family that grows along in the southern seashores of East Asia. It has been used as a tisane for treating cold and fever in Korea and a folk medicine for hepatitis in China. Recently, we have identified a few flavonoids in S. theezans leaves, including a novel flavonol glycoside, 7-O-methylmearnsetin 3-O-rhamnoside. In an effort to further identify the biological activity of the Sageretia theezans leaves, dried leaves were pulverized and extracted with 60% acetone and then fractionated sequentially with hexane, ethyl acetate, and water. Reactive oxygen radical species (ROS) (hypochlorite, peroxynitrite, and superoxide) scavenging activity, oxygen radical absorbance capacity (ORAC) value, and total phenolic content were tested in the crude extract and resulting fractions. Antioxidative effect of the fractions was also examined on the LDL resistance against copper ion-induced oxidation. The ethyl acetate fraction had the largest total phenolic content at 460 mg per gram dried weight and ORAC value and displayed the strongest ROS scavenging activity. The ethyl acetate fraction at physiological concentration prolonged the lag time of LDL oxidation by 260% as 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. 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. Epidemiological evidence also suggests an inverse relationship between intake of dietary flavonoids and risk of CVD. Therefore, our results implicate that the flavonoid-rich ethyl acetate fraction of S. theezans leaves may be a candidate material for use in functional foods and dietary supplements.
Technical Abstract: To explore their bioactive fractions, S. theezans leaves were extracted 2 with 60% acetone and then fractionated sequentially with hexane, ethyl acetate, and water. ROS (HOCl, ONOO-, and O2 deg -) scavenging activity, ORAC value and total phenolic content of each fraction were investigated. The ethyl acetate fraction had the largest total phenolics content and ORAC value and displayed the strongest ROS scavenging activity. The ethyl acetate fraction at 2 umol gallic acid equivalents (GAE)/L prolonged the lag time of LDL oxidation by 260% as compared to the control. In the ethyl acetate fraction, 7-O-methylmearnsetin 3-O-rhamnoside and the other 9 flavonols were characterized using HPLC 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 occupied 36% and 17% of the total flavonoid content, respectively.