HYPOCHOLESTEROLEMIC EFFECT OF SAPONIN EXTRACTS IN EXPERIMENTAL ANIMALS

Hypercholesterolemia was induced by feeding of rats on a high cholesterol diet (HCD) that contains cholesterol (1%), bile salts (0.25%) and coconut butter (15%) to evaluate the protective effect of steroidal saponins extracted from fenugreek and asparagus, and triterpenoidal saponins extracted from soapwort and licorice. The rats were divided into 6 groups, and the first one was fed on a basal diet and served as a negative control group. The second group of rats received HCD without any plant extract and served as a positive control group. The other four groups of rats were fed on HCD plus the plant extracts separately at a dose of 250 mg/kg/day during the experiment period (6 weeks). The protective effect of various saponin extracts were monitored through assays of total cholesterol (TC) and triglycerides (TG) in blood, liver tissues and feces of the rats as well as other blood analyses and histological examinations of liver tissues. The data indicated a significant (P<0.05) increase in the levels of TC, TG, low density lipoprotein (LDL), very low density lipoprotein (VLDL), creatine phosphokinase (CPK), lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma glutamyltransferase (GGT) and glucose, and a significant (P<0.05) decrease in the level of high density lipoprotein (HDL) in addition to insignificant (P<0.05) differences in the levels of total bilirubin (TB), total protein (TP), urea, creatinine and uric acid in serum of hypercholesterolemic rats (the positive control) compared to the negative control. The protective effect of various saponin extracts were established by lowering the levels of TC and TG, and obtaining the other biochemical parameters near to their  normal values in serum of rats fed on these plant extracts. The data also indicate that TC and TG decreased significantly (P<0.05) in liver tissues of the rats treated with various saponin extracts compared to the positive control. Conversely, the levels of TC and TG increased significantly (P<0.05) in feces of the rats treated with various saponin extracts compared to the negative and positive controls. Histological examinations showed lower content of fats in liver tissues of the rats treated with various saponin extracts compared to the positive control. Both of steroidal and triterpenoidal saponins exhibited approximately the same efficiency in their protective effects against hypercholesterolemia. The hypocholesterolemic effect of saponin extracts may be due to the inhibition of cholesterol absorption in the intestine which led to increase of cholesterol excretion in the feces.