Xuezhikang capsule (ethanol extract of red yeast rice) which produced by Beijing WBL Peking University Biotech Co., Ltd., is a traditional Chinese medication with 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibiting activity.  Clinical trials indicated that Xuezhikang with lipid-lowering action could reduce the risk of cardiac events and total mortality of Chinese coronary heart disease patients.  To exactly explain the clinical features of Xuezhikang, we undertook a complete study of the chemical constituents of Xuezhikang.  This study resulted in the isolation of a new monacolin analogue, named α, β-dehydromonacolin L (1), along with two known compounds: monacolin L (2) and 3-(2, 6-dimethyl-1, 2, 4a, 5, 6, 7, 8, 8a-octahydronaphthalen-1-yl)propanoic acid (3).  The chemical structures were determined by extensive 1D and 2D NMR and MS spectroscopic analysis.