| As a kind of commonly encountered disease, diabetes mellitus belongs to an endocrine dysfunction disease, characterized hyperglycemia, and long-drawn hyperglycemia will cause the increase of oxygen stress, and induce kinds of complications. Up to now the morbidity has been increasing, according to a study of WHO the patients in world have exceeded 120 million. In our country the morbidity in adult had achieved to 2.55% according to the mass survey in 1995. The mortality is only lower than that of tumor and cardiovascular diseases. So many countries in the world have been paid attention to find new hypoglycemic drugs, especially to sieve and study drugs from nature medicine, which exhibiting potent effect on diabetes induced complications too. Many nature drugs and their chemical constituents have been found their hypoglycemic effect.Mulberry leaf is the dried leaf of Morus alba which is a species of moraceae, also called "tie shanzi", "chanye", growing widely in our country, often collected in summer and autumn. Mulberry leaf is widely used in folk medicine for the treatment of cold, myelolymphangioma in lower limb, and so on. Modern pharmacology studies showed its effects of antibacterial, antineoplastic, expanding cardiovascular, lowering cholesterol, accelerating cell growth, vegetal estrogens along with hypoglycemic effect. The main effective chemical constituents contain steroid, triterpene, tonka bean camphor, and flavonoids etc. Recently the hypoglycemic effect of natural flavonoids is quietly causing people's attention. But before our study there is not yet any report about the hypoglycemic effect of the flavonoids from mulberry leaf (MTF).ObjectiveTo explore the effective constituents and the possible pharmacological activity, we extracted MTF, and investigated whose effect on blood glucose, disaccharidase, antioxidant enzymes, and nonenzymatic glucosylation of protein in alloxan (ALX) induced diabetic rat.Methods1 Extracting and identifying MTFThe ethanol extract of mulberry leaves was purified and condensed, which was then confected by water and PBS respectively to 0.8g(nature drug)/L.After the extract were identified by HCL-Mg powder test, aluminum salt complexion test and thin-layer chromatography, the total flavonoids were evaluated by rutoside standard curve.2 Pharmcalogical experiments2.1 Effect of MTF on blood glucose (BG) in rat: ALX-induced diabetic rats were distributed into 4 groups and treated for 4 weeks. Control, treated with NS (group C, 2ml/d); positive, with acarbose (group P, 20mg/kg-body weight); trail, with MTF low dose (group L, 8g/kg-body weight) and with MTF high dose (group H, 16g/kg-body weight). Additional set normal rats (group N, 8g/kg-body weight). The fasting plasma glucose (FPG) was assayed before and after treated. After treated, the rats were encountered an oral glucose tolerance test (OGTT), BG was assayed at 30min, 90min, I50min after glucose infused.2.2 Effect of MTF on disaccharidase in rats: The brush border membrane of the small intestine in diabetic rat was stripped and homolysed, which was incubated with MTF (0.8mg/L, 4.0mg/L, 8.0mg/L) in trail and PBS in control, and with disaccharide in vitro, then the inhibitory rate on disaccharidase was determined. Under anesthesia, blood from portal and peripheral veins was collected separately at 30min, 60min, 120min, after 20% maltose solution has injected into duodenum in vivo, then BG was measured and the BG difference between portal and peripheral vein was calculate.2.3 Effect of MTF on antioxidant enzymes: The activities of plasma GSH-Px and SOD in rats were measured before and after treated, after treated rats were sacrificed and the liver and spleen were excised, then the activities of homogenate GSH-Px and SOD were investigated too.2.4 Effect of MTF on nonenzymatic glucosylation of protein: The level of plasma glucosylated albumin in diabetic rats was assayed before and after treated in vivo. Glycosylation system was added different concentration (0.00 Ig/L, 0.1 g/L,...
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