Invited Symposium: Medicinal Plants and Drug Actions
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Li, J-P (Department of Pharmacology, Norman Bethune University, China)
Teoh, H (Department of Pharmacology, The University of Hong Kong, Hong Kong, China)
Man, RYK (Department of Pharmacology, The University of Hong Kong, Hong Kong, China)
Abstract
The oxidation of low density lipoprotein (LDL) is believed to be an important event in atherogenesis. Oxidized LDL, which is able to elicit some of the biological responses leading to the initiation and progression of the atherosclerotic plaque, is more atherogenic than native LDL. Ginkgo biloba is a traditional Chinese medicine which is used for treating peripheral vascular diseases and cereberovascular insufficiency. In vitro studies have shown that EGb, an extract from Ginkgo biloba leaves, scavenges various reactive oxygen species as well as peroxyl radicals. The present study was designed to investigate the protective effect of EGb on LDL oxidation. LDL samples were obtained from the plasma of healthy male donors by sequential ultracentrifugation. Native LDL was diluted to 50 µg protein per ml with phosphate buffered saline and then pretreated with various concentrations of EGb and/or vitamin C for 30 minutes. Oxidation of LDL was initiated with 2 µM CuSO4 at 37 oC for 180 min. Conjugated diene formation was measured by continuously monitoring the absorbance of LDL every 4 minutes in a Beckman spectrophotometer. In the range of 0.1-10 µg/ml, EGb concentration-dependently inhibited conjugated diene formation during LDL oxidation. Interestingly, a low concentration of EGb, 0.1 µg/ml, significantly enhanced the antioxidant effect of vitamin C on LDL oxidation. In addition, EGb concentration-dependently reduced lipid peroxide levels as measured by the amount of thiobarbituric acid-reactive substances (TBARS) formed and retarded the changes in relative electrophoretic mobilities (REM) of OxLDL samples. In conclusion, EGb can protect LDL from oxidation in vitro. The antioxidant action of EGb as well as its enhancement of other endogenous antioxidant effect provide further support for the potential anti-atherogenic role of EGb.
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Presentation Number SAhuang0808
Keywords: ginkgo biloba, LDL, oxidation
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