Objective: To study the hypoglycemic effects of soybean isoflavones (SI) and soyasaponins (SS) in diabetes, and their inhibitory activities on alpha-glucosidase (EC 3.2.1.20) and alpha-amylase (EC 3.2.1.1). Methods: GK/Jcl type 2 diabetic rats were given diet containing 20 g/kg of soybean hypocotyl extracts (SHE) for 20 weeks, then the blood glucose and oral glucose tolerance test were observed. SI and SS were isolated by ODS column chromatography and high-performance liquid chromatography (HPLC) from SHE. The inhibitory activities of each component of SI and SS against alpha-glucosidase and alpha-amylase were tested by colorimetric method. Results: SHE decreased blood glucose significantly in type 2 diabetic rats and improved glucose tolerance in both normal and diabetic rats. In alpha-glucosidase inhibitory assay, Group B, Group E and DDMP (2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one) saponins showed potent inhibitory activities with IC50 values of 10-40 靘ol/L. Isoflavone aglycones also showed potent inhibitory activities against alpha-glucosidase with IC50 values of 20-150 mol/L, while isoflavone glycosides showed a little lower potencies. Inhibition of SI and SS on alpha-amylase was low, and their inhibitory activities were about 10%~20% at the concentration of 1g/L. Conclusion: SI and SS may decrease blood glucose and improve oral glucose tolerance in diabetic rats, probably via the inhibitory effects on alpha-glucosidase and alpha-amylase.

OBJECTIVETo study the influence of soybean phytochemical extract containing isoflavones and soyasaponins (SPE) on blood glucose, blood lipids, plasma lipid peroxide and platelet aggregation activity in diabetic rats.

METHODSDiabetic rats were fed with fodder containing 20 g/kg of SPE for 20 weeks. Their plasma very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) were separated by sequential ultracentrifugation.

RESULTSTwenty weeks after experiment, level of blood glucose, atherosclerotic index and plasma level of lipid peroxide were (11.9 +/- 0.9) mmol/L, 0.40 +/- 0.14 and (15.7 +/- 0.5) mmol/L, respectively in diabetic rats fed with SPE, significantly lower than those in control rats not fed with it, (14.2 +/- 2.0) mmol/L, 0.58 +/- 0.22 and (20.7 +/- 3.0) mmol/L, respectively. Accordingly, platelet aggregation rates induced by ADP and collagen in the two groups were (54.1 +/- 8.8)% vs (66.6 +/- 12.4)% and (58.0 +/- 7.9)% vs (69.6 +/- 9.4)%, respectively. Changes in all these indices were significantly different between the two groups.

CONCLUSIONSPE could significantly decrease blood glucose, improve atherosclerotic index, and inhibit lipid peroxidation and platelet aggregation in diabetic rats, which might be useful in prevention and control of diabetes mellitus and diabetes-associated atherosclerosis.

Animals ; Arteriosclerosis ; blood ; prevention & control ; Cholesterol, HDL ; blood ; Cholesterol, LDL ; blood ; Cholesterol, VLDL ; blood ; Diabetes Mellitus, Type 2 ; blood ; prevention & control ; Flavonoids ; pharmacology ; Male ; Phytotherapy ; Random Allocation ; Rats ; Saponins ; pharmacology ; Soybeans ; Triglycerides ; blood