Protective action of ampelopsis cantoniensis and its major constituent – myricetin against LDL oxidation

It is widely accepted that oxidative modification of lowdensity lipoprotein (LDL) plays a pivotal role in the initiation and development of atherosclerosis. In the present study, we found that the MeOH and H2O extracts of the plant Ampelopsis cantoniensis, and its main constituent, myricetin, possessed significant protective effects on LDL oxidation induced by either a metal ion (Cu2+) or a free radical (AAPH).
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Protective action of ampelopsis cantoniensis and its major constituent – myricetin against LDL oxidationJournal of Chemistry, Vol. 45 (6), P. 768 - 771, 2007Protective Action of Ampelopsis cantoniensis and ItsMajor Constituent – Myricetin against LDL Oxidation Received 16 January 2007 1, 2 Do Thi Ha , Phuong Thien Thuong1, Nguyen Duy Thuan2 1 College of Pharmacy, Chungnam National University, Daejeon 305–764, South Korea 2 Department of Phytochemistry, National Institute of Medicinal Materials summary It is widely accepted that oxidative modification of lowdensity lipoprotein (LDL) plays a pivotal role in the initiation and development of atherosclerosis. In the present study, we found that the MeOH and H2O extracts of the plant Ampelopsis cantoniensis, and its main constituent, myricetin, possessed significant protective effects on LDL oxidation induced by either a metal ion (Cu2+) or a free radical (AAPH). All of these (MeOH ex., H2O ex., and myricetin) exhibited higher antioxidant activity than that of -tocopherol in a dose dependent manner, and especially, myricetin disclosed stronger inhibitory effect than that of (+)-catechin, a major component of green tea. The result suggests that the decoction of the medicinal plant “che day” could be used beneficially as a remedy to prevent the LDL oxidation involved in the atherosclerotic lesion. I - Introduction acute tonsillitis, acute bronchitis and tracheitis, and eczema in Vietnam [4, 5]. Previous studies Atherosclerosis, a disease of arteries have reported that total extracted flavonoidscharacterized by a local thickening of vessel revealed the anti-ulcer effect and goodwall that develops in the inner coat (tunica antioxidant activity of this plant [5]. Recently,intima), is the leading cause of death in the Thuong et al. reported the free radicalindustrial world. It has been recognized that scavenging and antioxidant properties of thethere are many risk factors that may cause MeOH and H2O extracts of this plant [4]. In theatherosclerosis in human [1]. Among them, the current study, we further investigated thatoxidative modification of LDL in artery wall is MeOH and H2O extracts, and its maingenerally accepted to play a key role in the constituent, myricetin, show significantinitiation and development of atherosclerosis [2]. antioxidant effects on LDL oxidation mediatedHence, inhibitory action of LDL oxidation by by either a metal ion Cu2+ or a free radicalsupplemental antioxidants is considered as an AAPH. This paper describes the isolation ofattractive therapeutic strategy to prevent myricetin, and the antioxidant properties of thisatherosclerosis and other related diseases [3]. compound, MeOH and H2O extracts from the A. cantoniensis (Hook. & Arn.) Planch title plant.(Vitaceae) is distributed in China, India, Japan,Vietnam, normally called Canton ampelopsis. II - Materials and MethodsThis is a wild plant used as a herbal to treatinflammatory diseases such as rheumatic- Plant material: The leaves of Ampelopsisarthritis, hepatitis, dermatitis, pyelitis, gastritis, cantoniensis Planch were collected in Lao Cai768province, Vietnam, in April 2004. The sample albumin as a standard [6, 7].was identified by Mr. Ngo Van Trai, National Cu2+- Mediated LDL Oxidation: The oxidationInstitute of Medicinal Materials, Hanoi, of LDL induced by copper ion was measured asVietnam. described previously [6, 7]. Briefly, LDL (100Extraction and Isolation of main compound: µg/ml) in PBS (pH 7.4, final volume of 1 ml)The leaves of A. cantoniensis (0.2 kg) were was pre-incubated with samples, and then 5 µMextracted with MeOH for 1 h (3 L x 3 times). CuSO4 was added to initiate the oxidation atThe MeOH extracts were combined, filled, and 37°C. The reaction was terminated by theexhaustively concentrated to give a MeOH addition of 1 µM EDTA and cooled at 4oC. Theextract (29.3 g). This crude extract was oxidation of LDL was monitored by measuringsuspended in water (300 mL) and partitioned the production of thiobarbituric acid reactivesuccessively with hexane, EtOAc (each 3 time x substances (TBARS) assay after 3 hrs300 mL), and then evapora ...