Intestinal Α-glucosidase Activity Research Articles

FT-IR analysis of Sapium ellipticum (Hochst) pax ethanol leaf extract and its inhibitory effects on pancreatic α-amylase and intestinal α-glucosidase activities in vitro

This study investigated the inhibitory effects of Sapium ellipticum (SE) (Hochst) Pax leaf extract on some carbohydrate metabolizing enzymes, pancreatic α-amylase and intestinal α-glucosidase activities in vitro. The inhibitory potential of SE extract was measured against Quercetin. SE extract in a dose dependent pattern significantly inhibited the activity of pancreatic α-amylase by 67.2% at 10 mg/mL. This effect was comparable to that of quercetin which offered 82.6% α-amylase inhibition. In terms of intestinal α-glucosidase activity, the inhibitory effect of the extract was significantly lower than that of quercetin at all investigated concentrations. At 10 mg mL−1 (maximum tested concentration), SE extract exhibited 35.8% inhibitory activity on α-intestinal glucosidase compared to the 74.3% exhibited by Quercetin at the same concentration. Phytochemical analysis results showed that SE contained 74 ± 3.12 milligram Gallic acid equivalents of total phenols and 67.2 ± 2.04 milligram Quercetin equivalents of flavonoids per gram of extract. Fourier Transformed Infra red spectroscopy (FT-IR) of SE extract revealed the presence of active functional groups reminiscence of polyphenols. Alpha amylase and α-glucosidase activities (in vivo) greatly contribute to postprandial hyperglycemia which is a great risk factor for type 2 diabetes mellitus. The inhibitory potential of SE extract on these enzymes as observed in this study suggests a positive and probable role of the extract in the management and treatment of diabetes mellitus, particularly, type 2.

Effect and potential mechanism of action of sea cucumber saponins on postprandial blood glucose in mice.

Postprandial blood glucose control is the major goal in the treatment of diabetes. Here, we investigated the effect of sea cucumber saponins (SCSs) on postprandial blood glucose levels. SCS inhibited yeast as well as rat intestinal α-glucosidase activity in a dose-dependent manner and showed better inhibition of yeast α-glucosidases compared to the positive control. Further studies were performed using ICR mice treated with SCS and starch or SCS alone by oral gavage. Unexpectedly, SCS increased postprandial blood glucose levels a short time (1h) after oral gavage. The serum corticosterone (CORT) level showed a consistent correlation with glucose levels. In vitro experiments confirmed that SCS treatment increased the secretion of CORT in the Y1 adrenal cell line. Overall, these studies demonstrated that SCS gavage could inhibit α-glucosidase activity but cannot attenuate postprandial blood glucose level within short time periods. The underlying mechanisms are probably related to increased serum CORT levels.

Fermentation of purple Jerusalem artichoke extract to improve the α-glucosidase inhibitory effect in vitro and ameliorate blood glucose in db/db mice.

BACKGROUND/OBJECTIVESJerusalem artichoke has inhibitory activity against α-glucosidase and decreases fasting serum glucose levels, which may be related to its fructan content. The biological activity of fructan can be influenced by the degree of polymerization. Thus, in this study, the inhibitory effects of original and fermented purple Jerusalem artichoke (PJA) on α-glucosidase were compared in vitro. Additionally, the anti-diabetes effect of Lactobacillus plantarum-fermented PJA (LJA) was studied in a non-insulin-dependent diabetes mellitus animal model (C57BIKsJ db/db).MATERIALS/METHODSThe water extract of PJA was fermented by L. plantarum, and two strains of Bacillus subtilis to compare their anti-α-glucosidase activities in vitro by α-glucosidase assays. The anti-diabetes effect of LJA was studied in a non-insulin-dependent diabetes mellitus animal model (C57BIKsJ db/db) for seven weeks. During the experiment, food intake, body weight, and fasting blood glucose were measured every week. At the end of the treatment period, several diabetic parameters and the intestinal α-glucosidase activity were measured.RESULTSThe LJA showed the highest α-glucosidase inhibitory activity in vitro. In the in vivo study, it resulted in a significantly lower blood glucose concentration than the control. Serum insulin and HDL cholesterol levels were significantly higher and the concentrations of triglycerides, non-esterified fatty acids, and total cholesterol were significant lower in mice treated with LJA after seven weeks. In addition, the intestinal α-glucosidase activity was partially inhibited.CONCLUSIONSThese results suggested that LJA regulates blood glucose and has potential use as a dietary supplement.

Hypoglycaemic potential of leaf extracts of Lonchocarpus cyanescens (Schum. and Thonn) Benth

This study evaluated the in vitro inhibitory effects of different extracts of L. cyanescens leaf on the activities of diabetes-related enzymes (α-amylase and α-glucosidase) and the effect of its ethanol extract on postprandial hyperglycaemia in starch-loaded rats. Results of this study revealed ethanol extract as the most potent inhibitor of α-amylase (IC50: 3.69 mg/ml) and α-glucosidase (IC50: 0.13 mg/ml). Lineweaver–Burk plots of the enzyme kinetics showed that the mode of inhibition of α-amylase by the ethanol extract of L. cyanescens is competitive, while it inhibited α-glucosidase non-competitively. Administration of ethanol extract of L. cyanescens leaf to starch-loaded Wistar rats significantly (p < 0.05) reduced the postprandial blood glucose level of the rats within two hours compared to the control animals. This study suggests that ethanol leaf extract of L. cyanescens possessed hypoglycaemic effect, and that one of the mechanisms by which this extract elicited its hypoglycaemic property may be through the inhibition of diabetes-related enzymes (pancreatic α-amylase and intestinal α-glucosidase) activities.

Dietary supplementation with fermented legumes modulate hyperglycemia and acetylcholinesterase activities in Streptozotocin-induced diabetes

The study investigated the hypoglycemic and anticholinesterase activities of some fermented legumes (bambara groundnut and locust bean) in Streptozotocin (STZ)-induced diabetic rats. The rats were made diabetic by intraperitoneal administration of STZ (35mg/kg b.w.) and were fed diets containing fermented legumes (10% inclusion) for 14 days. The effect of the diets on blood glucose, pancreatic glutathione peroxidase (GPx) activity, reduced glutathione (GSH) and malondialdehyde (MDA) contents, α-amylase, intestinal α-glucosidase and acetylcholinesterase activities were studied. Significant (P<0.05) increase in blood glucose, pancreatic MDA, α-amylase, intestinal α-glucosidase and acetylcholinesterase activities with concomitant decrease in pancreatic GPx and GSH contents were observed in diabetic rats. However, this trend was reversed in rats fed fermented legumes supplemented diets for 14 days. The HPLC–DAD finger printing revealed the presence of gallic acid, catechin, caffeic acid, epicatechin, rutin, isoquercitrin, quercitrin, quercetin and kaempferol as the dominant phenolic compounds of the fermented legumes. However, possible contributing role of some bioactive peptides could not be ruled out. Hence, the hypoglycemic and antiacetylcholinesterase activities of the fermented legume condiments could be attributed to their constituent phytochemicals.

Contribution of Musa paradisiaca in the inhibition of α-amylase, α-glucosidase and Angiotensin-I converting enzyme in streptozotocin induced rats.

Unripe plantain based-diets are part of folklore remedy for the management of diabetes in tropical Africa; however, with the dearth of information on the rationale behind this practice; this study therefore, sought to investigate the antihyperglycemic effect of traditional unripe plantain products (Amala and Booli) in high fat fed/low dose streptozotocin-induced diabetic rats and to provide a possible rationale for their antidiabetic properties. Diabetes was induced experimentally by high fat fed/low dose streptozotocin-diabetic rats (25mg/kg body wt.) and the diabetic rats were fed diets supplemented with 20-40% Amala and Booli for 14 days. The effect of the diets on the blood glucose level, pancreatic α-amylase, intestinal α-glucosidase and Angiotensin-I converting enzyme (ACE) activities and plasma antioxidant status as well as amylose/amylopectin content of the unripe plantain products were determined. A marked increase in the blood glucose, α-amylase, α-glucosidase and ACE activities with a corresponding decrease in plasma antioxidant status was recorded in diabetic rats. However, these indices were significantly (P < 0.05) reversed after unripe plantain product supplemented diet treatments for 14 days. Also, the amylose/amylopectin ratio of the products is 1:3. This study revealed that unripe plantain products exert antihyperglycemic effects which could be attributed to the inhibition of α-amylase and α-glucosidase activities by their constituent phytochemicals as well as their amylose/amylopectin contents in the diabetic rats, hence, providing the possible rationale behind their antidiabetic properties.

Selected tea and tea pomace extracts inhibit intestinal α-glucosidase activity in vitro and postprandial hyperglycemia in vivo.

Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by postprandial hyperglycemia, which is an early defect of T2DM and thus a primary target for anti-diabetic drugs. A therapeutic approach is to inhibit intestinal α-glucosidase, the key enzyme for dietary carbohydrate digestion, resulting in delayed rate of glucose absorption. Although tea extracts have been reported to have anti-diabetic effects, the potential bioactivity of tea pomace, the main bio waste of tea beverage processing, is largely unknown. We evaluated the anti-diabetic effects of three selected tea water extracts (TWE) and tea pomace extracts (TPE) by determining the relative potency of extracts on rat intestinal α-glucosidase activity in vitro as well as hypoglycemic effects in vivo. Green, oolong, and black tea bags were extracted in hot water and the remaining tea pomace were dried and further extracted in 70% ethanol. The extracts were determined for intestinal rat α-glucosidases activity, radical scavenging activity, and total phenolic content. The postprandial glucose-lowering effects of TWE and TPE of green and black tea were assessed in male Sprague-Dawley (SD) rats and compared to acarbose, a known pharmacological α-glucosidase inhibitor. The IC50 values of all three tea extracts against mammalian α-glucosidase were lower or similar in TPE groups than those of TWE groups. TWE and TPE of green tea exhibited the highest inhibitory effects against α-glucosidase activity with the IC50 of 2.04 ± 0.31 and 1.95 ± 0.37 mg/mL respectively. Among the specific enzymes tested, the IC50 values for TWE (0.16 ± 0.01 mg/mL) and TPE (0.13 ± 0.01 mg/mL) of green tea against sucrase activity were the lowest compared to those on maltase and glucoamylase activities. In the animal study, the blood glucose level at 30 min after oral intake (0.5 g/kg body wt) of TPE and TWE of both green and black tea was significantly reduced compared to the control in sucrose-loaded SD rats. The TPE of all three teas had significantly higher phenolic content than those of the TWE groups, which correlated strongly with the DPPH radical scavenging activity. This is the first report of tea pomace extract significantly inhibits intestinal α-glucosidase, resulting in delayed glucose absorption and thereby suppressed postprandial hyperglycemia. Our data suggest that tea pomace-derived bioactives may have great potential for further development as nutraceutical products and the reuse of otherwise biowaste as valuable bioresources for the industry.

Comparing morphological, chemical and anti-diabetic characteristics of Puerariae Lobatae Radix and Puerariae Thomsonii Radix

Ethnopharmacological relevancePuerariae Lobatae Radix (PLR) and Puerariae Thomsonii Radix (PTR) are traditional Chinese medicines used for the treatment of diabetes and cardiovascular diseases. These two herbs are used interchangeably in clinical practice, even though they possess significantly different chemical profiles. In the case of Pueraria species, the misidentification is related to the multiple Chinese common names in clinical practice and variable pharmaceutical Latin names in different versions of the Pharmacopoeia of the People׳s Republic of China. In addition, there is lack of evidence demonstrating how the differences in the chemical profile would impact on the pharmacological activity of the two herbs. Therefore, the aim of this study was to compare the microscopic, phytochemical profiles and anti-diabetic activity of PLR and PTR so that the two species can be differentiated. Materials and methodsThe microscopic characteristics of the PLR and PTR were observed and measured by an optical microscope. The major compounds were quantified by ultra-performance liquid chromatography (UPLC) and total flavonoid content (TFC) colorimetric assay. The free radical scavenging capacity was assessed by 2,2-diphenyl-2-picrylhydrazyl (DPPH) antioxidant assays. Anti-diabetic activity was determined by the inhibition of porcine pancreatic α-amylase and rat intestinal α-glucosidase activities. ResultsMicroscopic results illustrated that the size of xylem vessels (PLR: 0.1390±0.0184mm; PTR: 0.0471±0.0109mm), number of fibre per bundle (PLR: 32.6800±2.8780; PTR: 16.5900±0.9982) and the size of fibre (PLR: 0.0075±0.0003mm2; PTR: 0.0025±0.0002mm2) in PLR were significantly greater than that in PTR (p<0.01). PLR possessed a significantly lower total starch content (PLR: 0.5288±1.2559mg starch/g DM; PTR: 76.7954±2.9905mg starch/g DM) and total dietary fibre content (PLR: 4.2886±0.3466g/100g DM; PTR: 12.4148±0.4541g/100g DM) as compared to PTR. Isoflavonoids including puerarin, daidzin, genistin and daidzein were the major chemical constituents in both species. However, the average content of puerarin in PLR was found to be eleven times greater than that in PTR. Furthermore, the TFC, DPPH free radical scavenging capacity, anti-α-amylase and anti-α-glucosidase in the PLR extracts were 4.42, 4.91, 3.10 and 4.22 times greater than in the PTR extracts. ConclusionsThis study provides a comprehensive investigation on the two medicinal valuable Pueraria species and allows differences to be ascertained. This information can be used to update monographs which will help practitioners and dispensers differentiate the herbs. Further study on the interchangeable use of PLR and PTR in clinical practice is urgently warranted.

Screening and structural characterization of potential α-glucosidase inhibitors from Radix Astragali flavonoids extract by ultrafiltration LC-DAD-ESI-MSn

Inhibition of intestinal α-glucosidase activity is one important mechanism for the management of diabetes mellitus (DM).

Inhibitory effect of black tea and its combination with acarbose on small intestinal α-glucosidase activity

Ethnopharmacological relevanceIt is said that black tea is effective against type 2 diabetes mellitus because it can help modulate postprandial hyperglycemia. However, the mechanism underlying its therapeutic and preventive effects on type 2 diabetes mellitus is unclear. In this study, we focused on the effect of black tea on the carbohydrate digestion and absorption process in the gastrointestinal tract. We examined whether black tea can modulate postprandial hyperglycemia. Materials and methodsThe freeze-dried powder of the aqueous extract of black tea leaves (JAT) was used for in vitro studies of α-amylase activity, α-glucosidase activity, and glucose uptake by glucose transporters in Caco-2 cells; ex vivo studies of small intestinal α-glucosidase activity; and in vivo studies of oral sugar tolerance in GK rats, an animal model of nonobese type 2 diabetes mellitus. ResultsHalf maximal inhibitory concentration values indicated that JAT significantly reduced α-glucosidase activity, but weakly reduced α-amylase activity. Kinetic studies of rat small intestinal α-glucosidase activity revealed that the combination of JAT and the α-glucosidase inhibitor, acarbose, showed a mixed-type inhibition. JAT had no effect on the uptake of 2′-deoxy-d-glucose by glucose transporter 2 (GLUT2) and the uptake of α-methyl-d-glucose by sodium-dependent glucose transporter 1 (SGLT1). In the oral sucrose tolerance test in GK rats, JAT reduced plasma glucose levels in a dose-dependent manner compared with the control group. The hypoglycemic action of JAT was also confirmed: JAT, in combination with acarbose, produced a synergistic inhibitory effect on plasma glucose levels in vivo. In contrast to the oral sucrose tolerance test, JAT showed no effect in the oral glucose tolerance test. ConclusionsJAT was demonstrated to inhibit the degradation of disaccharides into monosaccharides by α-glucosidase in the small intestine. Thereby indirectly preventing the absorption of the dietary source of glucose mediated by SGLT1 and GLUT2 transporters localized at the apical side of enterocytes in the small intestine. The results indicate that black tea could be useful as a functional food in the dietary therapy for borderline type 2 diabetes mellitus that could modulate postprandial hyperglycemia.

Effect of fermented soybean condiment supplemented diet on α-amylase and α-glucosidase activities in Streptozotocin-induced diabetic rats

Inverse correlation exists between soybean consumption and incidences of some degenerative diseases such as diabetes. Thus, this work sought to investigate the antidiabetic effects of fermented soybean diet in streptozotocin (STZ)-induced diabetic rats. The rats were made diabetic by intraperitoneal administration of STZ (35 mg/kg b.w.) and fed diets containing 10% fermented soybean for 14 days. The effect of the diet on blood glucose, pancreatic glutathione peroxidase (GPx) activity, reduced glutathione (GSH) and thiobarbituric acid reactive species (TBARS) contents, α-amylase and intestinal α-glucosidase activities were investigated. Marked increase in the blood glucose, TBARS, α-amylase and intestinal α-glucosidase with corresponding decrease in pancreatic GPx and GSH contents were observed in diabetic rats. These trends were however, reversed in diabetic rats fed diet supplemented with fermented soybean for 14 days. Also, extract of the fermented soybean exhibited α-amylase and α-glucosidase inhibitory activity in vitro. The proximate composition of the fermented soybean revealed high crude protein content. Furthermore, the HPLC analysis of the soybean product indicated the presence of some phenolic phytochemicals. Thus, the antidiabetes property of the fermented soybean condiment may be attributed to the influence of its constituent phytochemicals on starch digestion and, α-amylase and α-glucosidase activities.

Naringenin inhibits α-glucosidase activity: A promising strategy for the regulation of postprandial hyperglycemia in high fat diet fed streptozotocin induced diabetic rats

Obesity and the onset of diabetes are two closely linked medical complications prevalent globally. Postprandial hyperglycemia is one of the earliest abnormalities of glucose homeostasis associated with type 2 diabetes (T2D). Postprandial glucose levels can be regulated through α-glucosidase inhibition. The present study aims to demonstrate the potent inhibitory role of naringenin against α-glucosidase activity. The mode of inhibition of naringenin was examined by measuring enzyme activity in vitro with different concentrations of substrate using Lineweaver–Burk plot analysis. It shows competitive inhibition towards mammalian α-glucosidase thereby competing with α-limit dextrins and oligosaccharide residues for binding in the active site. Similar results have been obtained from the molecular docking analyses, where naringenin shows preferential binding for the active sites in each of the evaluated human intestinal α-glucosidase enzymes. Post-docking intramolecular hydrogen bonding analysis shows water molecule mediated hydrogen bonding for N-terminal maltase glucoamylase and N-terminal sucrase isomaltase. Naringenin’s docked pose in the C-terminal maltase glucoamylase active site does not show any particular water mediated interaction similar to the co-crystallized acarbose. Further, our results suggest that naringenin (25mg/kg) exerts significant inhibition of intestinal α-glucosidase activity in vivo thereby delaying the absorption of carbohydrates in T2D rats, thus resulting in significant lowering of postprandial blood glucose levels. Both in vitro and in vivo results were compared to the commercially available α-glucosidase inhibitor acarbose. Our findings clearly indicate that naringenin dampens postprandial glycemic response and offers a potential complementary approach in the management of T2D.

Inhibitory effects of n-hexane fraction from hydro-methanolic (2:3) extract on α-amylase and α-glucosidase activities of sepal of Salmalia malabarica: An approach through in vitro study

The antidiabetic therapeutic approach is to reduce gastrointestinal glucose production and absorption through the inhibition in carbohydrate-digesting enzymes such as α-amylase and α-glucosidase. The present study was designed to investigate the α-amylase and α-glucosidase inhibition in the n-hexane fraction of sepal of Salmalia malabarica. The fraction showed concentration-dependent α-amylase (IC50 = 50.17 mg/L) and α-glucosidase (IC50 = 61.04 mg/L) inhibitory activity. The positive in vitro enzyme inhibition tests results were confirmed with an oral starch tolerance test with 18 hour fasted normoglycemic rats. Phytochemical study of the said plant part fraction revealed that is rich in total phenolic contents, flavonoids, and flavonol, which may be responsible for its pharmacological activity. In an acute toxicity study, the n-hexane fraction up to the dose level of 3000 mg/kg body weight did not exhibit any lethality or toxic symptoms. From these results, it may be concluded that the n-hexane fraction may have an inhibitory effect on intestinal α-amylase and α-glucosidase activity, and can be used effectively as a safer alternative therapy to control postprandial hyperglycemia.

Protective Effects of Dietary 1,5-Anhydro-d-glucitol as a Blood Glucose Regulator in Diabetes and Metabolic Syndrome

1,5-Anhydro-D-glucitol (1,5-AG) is fairly widespread in food products. It is also one of the major polyols in the human body, and its concentration is homeostatically regulated. We report here on the beneficial effects of 1,5-AG in preventing hyperglycemia and its role in improving metabolic syndrome. The findings revealed that it does not affect blood glucose levels itself under normal conditions but clearly has a suppressive effect on the levels of dietary sugars, such as glucose, maltose, and sucrose. A long-term administration study revealed that feeding db/db diabetic mice 3% 1,5-AG for 8 weeks significantly decreased blood glucose levels compared to untreated mice (339 ± 30 versus 438 ± 34 mg/dL; p < 0.05). Furthermore, this treatment also significantly suppressed serum cholesterol levels (110.2 ± 18.0 versus 168.4 ± 9.8 mg/dL; p < 0.01). 1,5-AG did not inhibit intestinal α-glucosidase activities but regulated liver glucose levels via affecting both the glycogenolysis and gluconeogenesis pathways. Furthermore, the oral administration of 1,5-AG significantly increased urinary glucose excretion in hyperglycemic conditions. These results clearly suggest that dietary 1,5-AG acts as a modulator of glucose levels in hyperglycemia. 1,5-AG therefore represents a new class of promising functional sweeteners, where the daily consumption of 1,5-AG with meals could inhibit the progress of hyperglycemia and metabolic syndrome.

Modulation of Starch Digestion for Slow Glucose Release through “Toggling” of Activities of Mucosal α-Glucosidases

Starch digestion involves the breakdown by α-amylase to small linear and branched malto-oligosaccharides, which are in turn hydrolyzed to glucose by the mucosal α-glucosidases, maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI). MGAM and SI are anchored to the small intestinal brush-border epithelial cells, and each contains a catalytic N- and C-terminal subunit. All four subunits have α-1,4-exohydrolytic glucosidase activity, and the SI N-terminal subunit has an additional exo-debranching activity on the α-1,6-linkage. Inhibition of α-amylase and/or α-glucosidases is a strategy for treatment of type 2 diabetes. We illustrate here the concept of "toggling": differential inhibition of subunits to examine more refined control of glucogenesis of the α-amylolyzed starch malto-oligosaccharides with the aim of slow glucose delivery. Recombinant MGAM and SI subunits were individually assayed with α-amylolyzed waxy corn starch, consisting mainly of maltose, maltotriose, and branched α-limit dextrins, as substrate in the presence of four different inhibitors: acarbose and three sulfonium ion compounds. The IC(50) values show that the four α-glucosidase subunits could be differentially inhibited. The results support the prospect of controlling starch digestion rates to induce slow glucose release through the toggling of activities of the mucosal α-glucosidases by selective enzyme inhibition. This approach could also be used to probe associated metabolic diseases.

Serviceberry [Amelanchier alnifolia (Nutt.) Nutt. ex. M. Roem (Rosaceae)] leaf extract inhibits mammalian α-glucosidase activity and suppresses postprandial glycemic response in a mouse model of diet-induced obesity and hyperglycemia

Ethnopharmacological relevanceServiceberry or Saskatoon berry [Amelanchier alnifolia (Nutt.) Nutt. ex. M. Roem (Rosaceae)], native to the North Glacier forests of the Rocky Mountains in Montana, has been used by the Blackfeet Indian tribe in alleviation of diabetes. Anecdotally, tea made from twigs and leaves have been used for optimum health and diabetes management. However, such traditional knowledge of the medicinal properties of Amelanchier alnifolia has not been validated by scientific studies. The goal of this study was to identify potential antidiabetic mechanisms of serviceberry. Materials and MethodsServiceberry plant samples consisting of leaves, twigs, and leaves with berries were extracted and fractionated. Ethyl acetate and water fractions were tested for inhibition of α-glucosidase activity in vitro. Diet-induced obese, hyperglycemic C57Bl6 mice were administered serviceberry leaf extract prior to sucrose-, starch-, or glucose-loading to test for α-glucosidase inhibition and decreased post-prandial glycemic response. ResultsIn the course of screening for potential antidiabetic mechanisms, serviceberry leaf extracts and subfractions demonstrated potent inhibitory activity against mammalian intestinal α-glucosidase activity (EC 3.2.1.20). Further, in an animal model of diet-induced obesity and hyperglycemia, serviceberry leaf subfraction demonstrated significant inhibition of intestinal α-glucosidase activity, and delayed the absorption of carbohydrates, resulting in significant lowering of post-prandial blood glucose concentrations, similar to the antidiabetic drug Acarbose™. ConclusionsThese findings indicating that serviceberry leaf extract may lower post-prandial glycemic response corroborate traditional knowledge of the Blackfeet Indians of Montana, and potentially offer a complementary approach in the treatment of diabetes.

Inhibitory effects of five medicinal plants on ratalpha-glucosidase: Comparison with their effects on yeast alpha-glucosidase

The mammalian and yeast α-glucosidase inhibitory activities of Senna italica, Tinospora fragosa, Manilkara mochisia, Xanthocercis zambesiaca, Ozoroa cf. albicans, Peltophorum africanum, Cassia abbreviata were investigated using p-nitrophenyl glucopyranoside as a substrate. All the plant species tested had low inhibitory activity against rat intestinal α-glucosidase. The highest concentration of C. abbreviata resulted in no observable loss of rat intestinal α-glucosidase activity. At 2.5 mg/ml, X. zambesiaca managed only 25% inhibition of rat intestinal glucosidase activity. M. mochisia led to about 60% loss of activity at 5 mg/ml. On the other hand, all plant species tested had good inhibitory activity against Baker’s yeast α-glucosidase. These findings suggest that a chemical substance that inhibits yeast α-glucosidase activity will not necessarily inhibit mammalian α-glucosidase. The validatation of the antidiabetic activity of medicinal plant extracts, with the focus on the inhibition of carbohydrate-digesting enzymes, will require, in addition, investigation of mammalian enzymes. The antioxidant activity of these plant species was also investigated, with C. abbreviata and ascorbic acid as the positive controls. The IC50 values were estimated. P. africanum had good antioxidant activity with an IC50 value of 0.030 mg/ml, similar to the IC50 value resulting from the positive control, ascorbic acid. Key words: Diabetes mellitus, α-glucosidase activity, antioxidant activity, plant extracts.

Inhibitory effect of hydro-methanolic extract of seed of Holarrhena antidysenterica on alpha-glucosidase activity and postprandial blood glucose level in normoglycemic rat

The present experiment was conducted to search out the effect of hydro-methanolic extract of seed of Holarrhena antidysenterica on intestinal α-glucosidase activity in dose dependent manner and on the management of postprandial hyperglycemia in starch loaded rats. Activity of intestinal α-glucosidase was measured by in vitro method. Fasting blood glucose level was determined by single touch glucometer. Total phenol and flavonoids of seed extract of Holarrhena antidysenterica were estimated using gallic acid and quercetin standard curves, respectively. The degree of elevation in blood glucose level after starch administration was significantly (p<0.05) less by the extract in respect to the control. The said extract also inhibited α-glucosidase activity having an IC(50) of 0.52mg/ml. Phytochemical study revealed that the extract is rich in phenolic compounds (60.23mg of gallic acid equivalent/g of extract) and flavonoids (360.23mg of quercetin equivalent/g of the extract). The extract exerts its antihyperglycemic effect by retarding the carbohydrate absorption from intestine through the inhibition in α-glucosidase activity and therefore resists postprandial hyperglycemia.

The effect of heteroatom substitution of sulfur for selenium in glucosidase inhibitors on intestinal α-glucosidase activities

The synthesis of selenium analogues of de-O-sulfonated ponkoranol, a naturally occurring sulfonium-ion glucosidase inhibitor isolated from Salacia reticulata, and their evaluation as glucosidase inhibitors against two recombinant intestinal enzymes maltase glucoamylase (MGAM) and sucrase isomaltase (SI) are described.

Grape skin extract inhibits mammalian intestinal α-glucosidase activity and suppresses postprandial glycemic response in streptozocin-treated mice

Intestinal α-glucosidases are the key enzymes responsible for starch digestion and absorption and their inhibition has been proven effective in both preventing and treating diabetes through improvement of postprandial hyperglycaemia. This study, for the first time, identified that a Norton grape skin extract (GSE) significantly inhibited mammalian intestinal α-glucosidases but not other digestive enzymes including structurally relevant pancreatic α-amylase. Norton GSE inhibited rat intestinal α-glucosidases through a competitive mode with an IC50 of 0.384mg/ml. Further animal study revealed that the oral intake of Norton GSE (400mg/kg) significantly reduced postprandial blood glucose by 30.9% in the streptozocin-treated male C57BL/6J mice following starch challenge. These findings suggest that Norton GSE may have a unique property of suppressing postprandial blood glucose through a mechanism involving the inhibition of α-glucosidases, thereby providing a novel dietary opportunity for diabetes management.