Establishment of high-resolution bioassay profiling platform to screen α-glucosidase inhibitors from Malus hupehensis / 药学学报

italic>α-Glucosidase inhibitors play an important role in the treatment of diabetes. This study established a high-resolution bioassay profiling platform for rapidly screening α-glucosidase inhibitors in natural product extracts. Five α-glucosidase inhibitors were identified from Malus hupehensis, namely, 3-hydroxyphloridzin, quercetin-3-O-β-D-glucopyranoside, phloridzin, avicularin and quercitrin. The establishment and successful application of this platform provides a powerful tool for the efficient discovery of anti-diabetic active ingredients in complex systems.

Novel carbohydrate-triazole derivatives as potential α-glucosidase inhibitors / 中国天然药物

A series of novel pyrano[2, 3-d]trizaole compounds were synthesized and their α-glucosidase inhibitory activities were evaluated by in vitro enzyme assay. The experimental data demonstrated that compound 10f showed up to 10-fold higher inhibition (IC74.0 ± 1.3 μmol·L) than acarbose. The molecular docking revealed that compound 10f could bind to α-glucosidase via the hydrophobic, π-π stacking, and hydrogen bonding interactions. The results may benefit further structural modifications to find new and potent α-glucosidase inhibitors.

Antidiabetic and antioxidant activities of red seaweed Laurencia dendroidea

Objective: To investigate antidiabetic and antioxidant activities of the extract and fractions from Vietnamese red seaweed Laurencia dendroidea. Methods: The seaweed Laurencia dendroidea was extracted by using microwave-assisted extraction method in 80% methanol. The seaweed extract was then fractionated using different solvents (n-hexane, chloroform, ethyl acetate, butanol and water). These obtained fractions were evaluated for α -glucosidase inhibitory and antioxidant activities. Antioxidant activities were tested using DPPH, nitric oxide radical scavenging and metal chelating assays. The enzyme inhibition mode was determined using Lineweaver-Burk plot. For acidic and thermal stabilities, the ethyl acetate fraction was treated at pH 2.0 and 100 °C, respectively. The residual inhibitory activity of the fraction was calculated based on the initial inhibitory activity. For in vivo antidiabetic activity, mice were divided into four groups, including normal control, diabetic control, diabetic mice treated with ethyl acetate fraction and diabetic mice treated with gliclazide. Blood glucose level of treated mice during acute and prolonged treatments was measured. To evaluate the toxicity of the ethyl acetate fraction, the body weight changes and activities of liver function enzymes (aspartate transaminase, alanine transaminase and gamma-glutamyl transferase) were carried out. Results: The extract of Laurencia dendroidea showed strong α-glucosidase inhibitory and DPPH radical scavenging activities. Methanolic concentrations affected both α-glucosidase inhibitory and antioxidant activities. A 80% aqueous methanol was the suitable solvent for extraction of enzyme inhibitors and antioxidants. Among solvent fractions, ethyl acetate fraction had the highest inhibitory activities against α -glucosidase with a mixed type of inhibition and the strongest antioxidant activities, and was stable under acidic and thermal conditions. The ethyl acetate fraction treated diabetic mice significantly reduced blood glucose level compared with the diabetic control group (13.16 mmol/L vs. 22.75 mmol/L after 3 hours of treatment). Oral administration of ethyl acetate fraction did not exhibit toxicity at a dose of 100 mg/kg body weight as determined by body weight changes and liver biochemical parameters. Conclusions: Laurencia dendroidea could be a potential source for production of antidiabetic and antioxidative agents.

Antidiabetic and antioxidant activities of red seaweed Laurencia dendroidea

Objective: To investigate antidiabetic and antioxidant activities of the extract and fractions from Vietnamese red seaweed Laurencia dendroidea. Methods: The seaweed Laurencia dendroidea was extracted by using microwave-assisted extraction method in 80％ methanol. The seaweed extract was then fractionated using different solvents (n-hexane, chloroform, ethyl acetate, butanol and water). These obtained fractions were evaluated for α-glucosidase inhibitory and antioxidant activities. Antioxidant activities were tested using DPPH, nitric oxide radical scavenging and metal chelating assays. The enzyme inhibition mode was determined using Lineweaver-Burk plot. For acidic and thermal stabilities, the ethyl acetate fraction was treated at pH 2.0 and 100 ℃, respectively. The residual inhibitory activity of the fraction was calculated based on the initial inhibitory activity. For in vivo antidiabetic activity, mice were divided into four groups, including normal control, diabetic control, diabetic mice treated with ethyl acetate fraction and diabetic mice treated with gliclazide. Blood glucose level of treated mice during acute and prolonged treatments was measured. To evaluate the toxicity of the ethyl acetate fraction, the body weight changes and activities of liver function enzymes (aspartate transaminase, alanine transaminase and gammaglutamyl transferase) were carried out. Results: The extract of Laurencia dendroidea showed strong α-glucosidase inhibitory and DPPH radical scavenging activities. Methanolic concentrations affected both α-glucosidase inhibitory and antioxidant activities. A 80％ aqueous methanol was the suitable solvent for extraction of enzyme inhibitors and antioxidants. Among solvent fractions, ethyl acetate fraction had the highest inhibitory activities against α-glucosidase with a mixed type of inhibition and the strongest antioxidant activities, and was stable under acidic and thermal conditions. The ethyl acetate fraction treated diabetic mice significantly reduced blood glucose level compared with the diabetic control group (13.16 mmol/L vs. 22.75 mmol/L after 3 hours of treatment). Oral administration of ethyl acetate fraction did not exhibit toxicity at a dose of 100 mg/kg body weight as determined by body weight changes and liver biochemical parameters. Conclusions: Laurencia dendroidea could be a potential source for production of antidiabetic and antioxidative agents.

Anti-diabetic effects of the fraction of alkaloids from Ramulus Mori, an innovative Sangzhi alkaloids as an α-glucosidase inhibitor / 药学学报

Sangzhi alkaloids (SZ-A) are derived from traditional Chinese medicine Ramulus Mori, serving well as an innovative antidiabetic drug, due to α-glucosidase inhibition. To evaluate the potency of glucosidase inhibitory effect of SZ-A, the enzyme-based screening platforms, including sucrase, maltase and amylase were established, and IC50 was calculated. The effects of SZ-A on postprandial blood glucose at a single dose, oral sucrose, starch and glucose loading were determined in normal ICR mice and alloxan-induced hyperglycemic mice. To confirm the anti-diabetic effects of SZ-A on glucose and lipid metabolism after long-term administration, the postprandial and fasting blood glucose, serum insulin, urinary glucose levels, glycosylated serum proteins and blood lipid levels were determined in high-fat fed C57 obese mice (pre-diabetic HFC57 mice) and diabetic rats induced by streptozotocin (STZ). The Experimental Animal Welfare Ethics Committee of the Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College approved all of the protocols for this research. We found that SZ-A exhibited a significant inhibitory effect on the sucrase and maltase. SZ-A showed no effect on amylase. In normal ICR mice and alloxan-induced hyperglycemic mice, SZ-A at a single dose significantly delayed and reduced the peak of blood glucose after sucrose or starch loading, but showed no effect on the increase of blood glucose after glucose loading. In STZ diabetic rats, SZ-A significantly reduced the postprandial or fasting blood glucose levels, glycosylated serum proteins and urinary glucose. SZ-A also reduced serum triglyceride (TG) and cholesterol (TC) levels after 3 weeks of treatment. SZ-A ameliorated the postprandial blood glucose or the fasting blood glucose elevation, and reduced the incidence of hyperglycemia in HFC57 mice. SZ-A decreased the basal insulin level, improved insulin sensitivity, and ameliorated glucose intolerance in pre-diabetic HFC57 mice. Our results indicated that SZ-A had a novel inhibitory activity on α-glucosidase, especially on disaccharidases. SZ-A at a single dose significantly reduced the peak of blood glucose elevation and delayed the increase of blood glucose in normal and diabetic mice after disaccharide and polysaccharide loading. Long-term SZ-A treatment improved glucose and lipid metabolic profiles by delaying carbohydrate absorption from the intestine and reduced the postprandial blood glucose levels in both pre-diabetic and diabetic animal models. Therefore, SZ-A application may display a beneficial role in preventing the development and complications of diabetes.

Efficacy and mechanism of puerin Ⅰ in improving disorder of glycolipid metabolism in ApoE-/-mice / 中国中药杂志

Pu-erh tea is a unique post-fermented tea processed from tender leaves of Camellia assamica. Characteristic component puerins were produced during the microbial fermentation process.This study focuses on the therapeutic effect and mechanism of puerinⅠ(P1) in Pu-erh tea on ApoE-/- mice with dyslipidemia and diabetes. It was found that P1 could significantly decreased total cholesterol (TC), triglyceride (TG) and fast blood glucose (FBG), and markedly improved impaired glucose tolerance (IPGTT) and insulin sensitivity (ITT) in hyperlipidemic and hyperglycemic ApoE-/- mice. Further experiments proved that P1 reduced FBG and plasma TG levels by inhibiting intestinal α-glycosidase enzymes activity and by activating low-density lipoprotein receptor respectively. This study confirmed the therapeutic effect and mechanism of P1 on ApoE-/- mice with diabetes and hyperlipidemia. Based on the good efficacy of this compound, P1 could be used as a new drug to treat the disorder of glycolipid metabolism.

Reviews on α-glucosidase inhibitor from plant secondary metabolites / 中国中药杂志

α-Glucosidase inhibitor was a new type of antidiabetics which was developed in the late 1970s. By reducing the postprandial blood sugar concentration, it could effectively control the blood sugar levels, thereby reducing the occurrence of diabetic complications. Studies have shown that plant secondary metabolites have important biological functions such as hpyerglycemic, anti-hyperlipidemia, immunomodulatory, and antitumor effects. In this paper, the sources of plant secondary metabolites which are able to inhibit α-glucosidase and their inhibition mechanism would be reviewed to provide references for seeking more safe and efficient plant secondary metabolites of α-glucosidase inhibitors.

Screening of theα-Glucosidase Inhibitory Active Part from Yao Medicine Pothos chinensis / 中国药房

OBJECTIVE:To screen the α-glucosidase inhibitory active part from Pothos chinensis. METHODS:The aqueous extractions of P. chinensis were extracted by petroleum,ethyl acetate,n-butyl alcohol in turn to obtain different polarparts. Effect of each part on α-glucosidase inhibitory activity was determined,and enzyme inhibition kinetics was conducted for the screened parts with strong activity and relatively high yield rate;effects of each part on blood glucose level of mice loaded with glucose,su-crose and starch were respectively determined (using Acacoside tablet as positive control). RESULTS:Enzyme inhibition kinetics in vitro showed the ethyl acetate part [yield rate was 0.40%,enzyme activity inhibition rate was(72.90±2.85)%] had strongα-glu-cosidase inhibitory activity and showed a dose-dependent,fast,non-competitive and reversible model. Results of in vivo glucose tol-erance indicated that Acacoside tablet and each part of P. chinensis had no effects on blood glucose level of glucose-loaded mice (P>0.05);while Acacoside tablet and ethyl acetate part in P. chinensis could reduce 30,60 min blood glucose level of su-crose-loaded mice and 30,60,120 min blood glucose level of starch-loaded mice(P<0.05 or P<0.01). CONCLUSIONS:Ethyl acetate part is theα-glucosidase inhibitory active part from Yao medicine P. chinensis.

Synthesis, biological activity and molecular docking research of N-{(4-oxo-thiochroman-3-yl)phenyl-methyl}acetamide derivatives as α-glucosidase inhibitors / 药学学报

In order to develop potent antidiabetic agents that have inhibitory effect to α-glucosidase, twelve β-acetamido ketone derivatives such as N-{[(substituted-4-oxo-thiochroman-3-yl)phenyl]-methyl}acetamide are designed and synthesized through one-pot Dakin-West reaction. Their chemical structures are confirmed by 1H NMR, 13C NMR, IR and HR-MS. In vitro α-glucosidase inhibition assays of compounds 4a-4l were carried out using glucose oxidase method. The result indicated that most of them possess inhibitory activity in vitro. Compound 4k showed the most potent inhibitory activity with 87.3% inhibition of α-glucosidase at the concentration of 5.39 mmol·L-1. The structure-activity relationship of these β-acetamido ketone derivatives was discussed preliminarily. Moreover, the molecular docking method was used to study the interaction mode of compound 4k and α-glucosidase. Our results will be helpful for designing of α-glucosidase inhibitors in the future.

Antioxidant and α-glucosidase inhibitor activities of natural compounds isolated from Quercus gilva Blume leaves

To isolate and investigate antioxidant and α-glucosidase inhibitor compounds in the leaves of Quercus gilva Blume (Q. gilva). Methods: Dry leaves of Q. gilva were extracted with methanol and the methanolic extract was further separated by silica gel column chromatography using several solvents with increasing polarity. The antioxidant activities of the isolated compounds were evaluated using various in vitro assays: 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, hydrogen peroxide radical scavenging activity, β-carotene bleaching assay, and reducing power assay. The α-glucosidase inhibitory assay was conducted against α-glucosidase from Saccharomyces cerevisiae. Results: Three compounds were isolated and their structures were identified as catechin (1), epicatechin (2), and tiliroside (3) using an instrumental analysis. Compound 2 had higher antioxidant activity with inhibitory concentrations (IC50) of (22.55 ± 2.23) μmol/L than that of quercetin, which was used as the standard, with an IC50 of (28.08 ± 2.39) μmol/L, followed by compound 1 with IC50 of (40.86 ± 3.45) μmol/L. On the other hand, compound 3 had the lowest antioxidant activity with an IC50 of (160.24 ± 8.15) μmol/L. However, compound 3 had the highest α-glucosidase inhibitory activity with an IC50 of (28.36 ± 0.11) μmol/L, followed by compounds 1 and 2 with (168.60 ± 5.15) and (920.60 ± 10.10) μmol/L, respectively. Conclusions: The results obtained for the antioxidant activities and α-glucosidase inhibitory activities in a methanolic extract from the leaves of Q. gilva confirmed the potential of this plant as a source of natural antioxidants and antidiabetic medicine.

Antioxidant and α-glucosidase inhibitor activities of natural compounds isolated from Quercus gilva Blume leaves

Objective: To isolate and investigate antioxidant and α-glucosidase inhibitor compounds in the leaves of Quercus gilva Blume (Q. gilva). Methods: Dry leaves of Q. gilva were extracted with methanol and the methanolic extract was further separated by silica gel column chromatography using several solvents with increasing polarity. The antioxidant activities of the isolated compounds were evaluated using various in vitro assays: 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, hydrogen peroxide radical scavenging activity, β-carotene bleaching assay, and reducing power assay. The α-glucosidase inhibitory assay was conducted against α-glucosidase from Saccharomyces cerevisiae. Results: Three compounds were isolated and their structures were identified as catechin (1), epicatechin (2), and tiliroside (3) using an instrumental analysis. Compound 2 had higher antioxidant activity with inhibitory concentrations (IC

Pharmacological Effect of α-Glucosidase Inhibitor Voglibose in a Novel Obese Diabetic Model.

Aim: This study was conducted to investigate the preventive or therapeutic effect of α- glucosidase inhibitor voglibose in a new model rat, Spontaneously Diabetic Torii-Leprfa (SDT fatty) rat, which is a novel type 2 diabetic rat showing obesity, hyperglycemia and hyperlipidemia from a young age. Place and Duration of Study: Niigata University and JT Central Pharmaceutical Research Institute, between January and August 2011. Methodology: The present study was designed to the preventive and therapeutic effect of voglibose by administering (0.3, 1 mg/kg) voglibose as a dietary admixture to SDT fatty rats from 5 to 11 and 14 to 20 weeks of age, respectively. Results: In the examination of preventive effect, the obtained biochemical results show that voglibose decrease glucose level significantly in dose-dependent manner within 5-11 weeks of age. In voglibose-treated rats at 11 weeks of age, the histopathological pancreatic changes, such as vacuolation and irregular boundaries in islets, were improved. On the other hand, in the examination of therapeutic effect, voglibose improved the hyperglycemia only at a dose of 1 mg/kg within 16-20 weeks of age. Conclusion: Voglibose showed both preventive and therapeutic effects for diabetes in female SDT fatty rats. The SDT fatty rat is a useful model for development of anti-diabetic agents.

Total synthesis of neokotalanol, a potent α-glucosidase inhibitor isolated from Salacia reticulata / 中国天然药物

Neokotalanol, a potent α-glucosidase inhibitor isolated from Salacia reticulata, was synthesized through a key coupling reaction between a perbenzylated thiosugar and an appropriately protected perseitol triflate derived from D-mannose. This key step was found to be quite temperature dependent, and a simultaneous cyclization of the triflate leading to a characteristic 2,4,7-trioxabicyclo[4.2.1]nonane system was detected.