Our previous study showed that a
triterpene mixture, consisting of
echinocystic acid (EA) and
oleanolic acid (OA) at a ratio of 4 : 1, dose-dependently ameliorated the
hyperlipidemia and
atherosclerosis in rabbits fed with high fat/high
cholesterol diets. This study was aimed at exploring the mechanisms underlying
antihyperlipidemic effect of EA. Molecular docking simulation of EA was performed using Molegro Virtual Docker (version: 4.3.0) to investigate the potential targets related to lipid metabolism. Based on the molecular docking information,
isotope labeling method or spectrophotometry was applied to examine the effect of EA on the activity of 3-hydroxy-3-methylglutaryl
coenzyme A (
HMG-CoA) reductase,
acyl-CoA:cholesterol acyltransferase (ACAT), and
diacylglycerol acyltransferase (DGAT) in rat liver microsomes. Our results revealed a strong affinity of EA towards ACAT and DGAT in molecular docking analysis, while low binding affinity existed between EA and
HMG-CoA reductase as well as between EA and
cholesteryl ester transfer protein. Consistent with the results of molecular docking, in vitro
enzyme activity assays showed that EA inhibited ACAT and DGAT, with IC50 values of 103 and 139 μ M, respectively, and exhibited no significant effect on
HMG-CoA reductase activity. The present findings suggest that EA may exert hypolipidemic effect by inhibiting the activity of ACAT and DGAT.