Mechanistic study on the antiatherogenic effect of fructus crataegi (Shan Zha)

Abstract

Cardiovascular disease (CVD) is the major source of morbidity and mortality in the developed world. Among the CVDs, atherosclerosis is the most serious because it can lead to other severe diseases like stroke, heart attack and coronary heart disease. Oxidation of low density lipoprotein is a critical factor for atherosclerosis. Shan Zha, also known as hawthorn and Crataegus, has long been a folk medicine in China, Europe and North America. It acts on liver, a site believed to affect the cholesterol metabolism. Apart from this, many antioxidants are found in Shan Zha. As a result, Shan Zha is believed to have an antiatherogenic effect. This study aimed to find out the mechanisms involved in the antiatherogenic effect of Shan Zha (Fructus crataegi), and whether the cholesterol metabolism and antioxidant mechanisms are the only mechanisms involved in the antiatherogenic effect or other mechanisms are involved as well. In the preliminary study of this project, the percentage vasorelaxation of rat isolated aortas from the normal group was significantly higher than that of the hypercholesterolemic group (p<0.05) at the acetylcholine concentration greater than 100 uM and Shan Zha group showed a tendency to reduce the atherogenic effect of the hypercholesterolemic diet. However, there is no difference in the contraction response among the groups, indicating that vasoconstriction is independent of the antiatherogenic effect. Antioxidant is believed to be antiatherogenic, and 80 % ethanol extract was found to be the most antioxidative. Thus, the 80 % ethanol extract was used for the mechanistic studies. Consuming 80 % ethanol Shan Zha extract for twenty-eight days significantly prevented hypertension and the loss of vascular elasticity caused by the hypercholesterolemic diet on rats. These effects are in a concentration-dependent manner. The protective effect existed without the presence of hypocholesterolemic effect. The plasma total cholesterol and low density lipoprotein of rat consuming Shan Zha was as high as those which consumed the hypercholesterolemic diet. The protective effect is independent of the increase of the antioxidative enzyme activities, as there were no significant differences in the superoxide dismutase, catalase and glutathione peroxidase activities among the groups. Furthermore, the relaxation ability was significantly lower when the endothelial cell was removed in the normal group and the group with Shan Zha consumption. However, there was no significant difference of those with or without the endothelial cell in the hypercholesterolemia group. This indicated that the protective effect was related to the endothelium cell. In this project, the anti-atherogenic effect was measured basing on the enhancement of the relaxation ability. However, ingredients of Shan Zha may cause vessel relaxation directly. In order to further examine whether the ingredients of Shan Zha cause vessel relaxation directly, the 80 % ethanol Shan Zha extract, chlorogenic acid and quercetin, two of the flavonoids found in Shan Zha were added instead of acetylcholine to the isolated aorta. Chlorogenic acid significantly caused vessel relaxation at 10 uM. A reliable HPLC analysis method was also developed for quantifying the chlorogenic acid and quercetin.