Biological Activity Of Woody Stem Of Asparagus Officinalis L

Asparagus (Asparagus officinalis L.) is a healthy and nutritious vegetable which possess antioxidant, hypolipidaemic and antitumour properties. The edible shoot of asparagus is about one-half to two-thirds of the full length of the stem, and the remaining woody part (inedible bottom part) is always discarded as by-product. However, this by-product of asparagus still contains many bioactive substances that have potential usage in food supplements and therapeutic effects.Therefore, in order to make full use of woody stem part of asparagus, its effects on serum glucose and lipid profiles in hyperlipidaemic mice and diabetic rats and cancer cell were investigated in the present study. Furthermore, the antitumour ingredient, saponins was screened out and its mechanism was studied.This dissertation includes three parts as follow:1. Hypolipidaemic and hypoglycaemic effects of asparagus woody stemFirstly, the chemical constitutes of ethanol and aqueous extracts of asparagus woody stem (EEA, AEA) were analyzed. Result showed that there were7.94%saponins,7.32%flavonoids and22.29%polysaccharides in ethanol extract, and2.50%saponins,3.50%flavonoids and36.45%polysaccharides in aqueous extract.In this work, a high-fat diet (HFD) fed mice model was used to investigate the effects of ethanol and aqueous extract of asparagus woody stem on lipid metabolism. Results indicated that continuous HFD feeding caused obvious hyperlipidaemia and liver damage in mice. However, EEA and AEA significantly decreased the levels of serum total cholesterol and low-density lipoprotein cholesterol in hyperlipidaemic mice when administered at a daily dose of200mg/kg for8weeks. And treatments of EEA and AEA significantly decreased alanine and aspartate transaminases activities, but markedly increased superoxide dismutase activity and total antioxidant capacity in liver of model mice. Moreover, serum high-density lipoprotein cholesterol levels were evidently increased after AEA treatment. These findings suggest that EEA and AEA have hypolipidaemic effect and might have hepatoprotective activity. The hypoglycaemic effect of the AEA was evaluated in a streptozotocin (STZ)-induced type1-like diabetic rat model and a HFD-low dose STZ induced type2-like diabetic rat model. Results showed AEA administration for21days significantly decreased fasting serum glucose and triglyceride levels but markedly increased body weight and hepatic glycogen level in type1-like diabetic rats. In an oral glucose tolerance test, both the blood glucose level measured at30,60and120min after glucose loading and the area under the glucose curve showed a significant decrease after AEA treatment. In type2-like diabetic rat model, AEA were orally administered to model rats once a day for45days. The results shown that administration of AEA significantly lowered the serum glucose and free fat acid levels, whereas increased high density lipoprotein cholesterol level in diabetic rats. Meanwhile, both blood glucose levels measured at60and120min after glucose loading and the area under the glucose curve in oral glucose tolerance test showed a significant decrease after AEA treatment. These results suggest that AEA might exhibit hypoglycemic and hypolipidemic effects, and could improve glucose tolerance in diabetic rats.2. Cytotoxic effect of asparagus woody stem and the extraction of saponinAs for the ethanol extracts of asparagus woody stem (EEA), prostate cancer PC3cell were used to evaluate its antitumor effect. Results showed that EEA exhibited obviously cytotoxic activity on cancer cell line, and IC50was1.5mg/ml.Saponin was extracted from EEA by n-butanol extraction and macroporous resin column purification. Furthmore the antitumor effect of saponins from woody stems of asparagus (SSA) was evaluated in6cancer cell lines and the results showed the cytotoxic effects of SSA on cancer cell lines in a concentration dependent manner.3. Antitumor activity of saponins from woody stems of asparagusIn this study, we demonstrated the cytotoxic effects of saponins from woody stems of asparagus (SSA) on cancer cell lines in a concentration dependent manner. Cytotoxic effects of SSA were examined using SRB method and the ability of inducing cancer cells apoptosis was analyzed by annexin V staining assay. The inhibitory activities of SSA on cancer cell motility were evaluated using wound-healing migration assay, Transwell migration assay and invasion assay. GST pull-down assay was performed to validate that SSA exerted inhibitory actions on cell metastasis through regulating the Rho GTPases signaling pathway. We evaluated SSA could significantly reduce the migratory and invasive ability of human breast cancer MDA-MB-231cells dose-dependently with an effective inhibitory concentrations of400μg/ml. In addition, when firstly came to the mechanism research, we found out the novel biological functions of SSA as an inhibitor of cell motility by regulating the activation of Rho GTPases in MDA-MB-231cells. Thus, overall, the findings of this study indicate that SSA inhibits the proliferation and motility of tumor cells through modulating Rho GTPases signaling pathway.