The Synthesis And Hypoglycemic Activity Of 2-O-β-D-Glucosyl-L-Ascorbic Acid And Its Analogues

Diabetes, a chronic metabolic disease, generally gives rise to cardiovascular disease. With the improvement of people’s living standard, agrowing number of people suffer from diabetes, which causes serious threat to human health and life. However, there is no effective way to completely cure diabetes. Diabetics have to rely on drugs to maintain blood glucose. Thus, it has great significance to find new, effective and reliable hypoglycemic drugs.2-O-(β-D-glucopyranosyl)-L-ascorbic acid(AA-2βG) is a kind of ingredients in wolfberry. Its specific β-configuration of the glycoside restrains the activity of α-glucosidase. Meanwhile, ascorbic acid can be produced by the hydrolysis of AA-2βG and protect the body and internal organs. Herein, we envisaged that this class of compounds may have the effect of lowering blood sugar. In this paper, in vitro enzyme assay and mouse in vivo experiment were conducted to investigate their hypoglycemic activity. The main contents are as follows:1. The reported synthetic route of AA-2βG was optimized. The key glycosylated step was achieved by 2,3,4,6-tetraacetylglucosyl bromide and 3,5,6-protected ascorbic acid. The total yield was increased from 13% to 50%. Subsequently, the synthesis of AA-3βG and AA-2βGal were realized using similar method.2. In vitro α-glucosidase inhibition experiments were performed. The experimental results showed that AA-2βG, AA-2βGal and AA-3βG could inhibit the activity of α-glucosidase. AA-2βG(IC50=0.98 mmol/L) and AA-2βGal(IC50=1.15 mmol/L) were superior to acarbose(IC50=4.54 mmol/L) for the inhibition of α-glucosidase from Saccharomyces cerevisiae. The docking analysis demonstrated that AA-2βG could interact with yeast α-glucosidase through three amino acid active sites, ASP214, GLU276 and ASP349. The binding sites of α-glucosidase interrelated with AA-2βGal was GLU276. However, AA-3βG bound in the enzyme through the only active site of ASP349. The simulation results further demonstrated that these β-glycosides inhibited α-glucosidase activity in a competitive manner and the inhibitory effect sequence followed AA-3βG< AA-2βGal< AA-2βG. These β-glycosides had no significant inhibitory effect on pancreatic α-amylase. These β-glycosides had different inhibitory effect on intestinal α-glucosidase extracted from mouse and AA-3βG(IC50=67.19 mmol/L) provided the best result.3. The hypoglycemic effect of AA-2βG and its derivatives on mouse was investigated through in vivo experiments. The experimental results showed that AA-2βG, AA-2βGal and AA-3βG could lower postprandial blood glucose. For the maltose tolerance experiments, the normal mice were given by gavage with AA-2βGal and AA-3βG, respectively. Compared with the control group, the rate of postprandial blood glucose rise decreased from 50% to 35% in 30 min and return to fasting blood glucose level after 60 min. The starch tolerance experiments: the normal mice feeding with starch were given by gavage with AA-2βG and AA-2βGal, respectively. Compared with the control group, the rising rate of postprandial blood glucose decreased from 64% to 20% in 30 min and return to fasting blood glucose level after 120 min. The diabetic mice administrated with maltose were given by gavage with AA-2βG, AA-2βGal and AA-3βG, the effect of lowering blood sugar was obvious. Compared with the control group, the postprandial blood glucose fluctuated slightly and increased less than 10% in 30 min and returned to fasting blood glucose level after 80 min. The diabetic mice administrated with starch were given by gavage with AA-2βG, AA-2βGal and AA-3βG, the effect of lowering blood sugar was obvious. Compared with the control group, the postprandial blood glucose fluctuated slightly and increased less than 18% in 30 min and returned to fasting blood glucose level after 60 min.