Inhibit Alpha-amylase Activity Research Articles

In Vitro Hypoglycemic and Radical Scavenging Activities of Certain Medicinal Plants

Abstract The purpose of this study is to investigate in vitro hypoglycemic and free radical scavenging activities of some medicinal plants including Ficus glomerata (FG), Pandanus amaryllifolia (PaA), Artocarpus altilis (AA), Gomphrena celosioides (GC) and Gynostemma pentaphyllum (GP). Alpha-amylase inhibitory assay was examined by dinitrosalicylic acid reaction. Glucose uptake assay was investigated by LO-2 cell model. DPPH and ABTS+ scavenging assays were performed by spectrophotometry. Cell viability was determined by MTT method. It was found that the extracts including FG, PaA, AA, GC and GP were able to inhibit alphaamylase activity up to 38.4 ± 4.2%, 47.8 ± 4.3%, 49.3 ± 3.5%, 40.1 ± 4.4% and 38.5 ± 3.8%, respectively. Moreover, glucose adsorption and glucose uptake capacity of these extracts were evidenced. In addition, free radical scavenging activity of these extracts was indicated in a range of 30.6-54.5% for DPPH radical and 31.8-51.1% for ABTS+ radical. Especially, these extracts exhibited no cytotoxicity effect on human hepatic LO-2 cells and human gastric BGC-823 cells at the concentration of 100 μg/ml. The results indicated that A. altilis leaves were effective in inhibiting alpha-amylase activity, increasing glucose adsorption and glucose uptake and scavenging free radicals. Therefore, it could be suggested to be a promising hypoglycemic agent for managing type 2 diabetes.

Studies of the anti-hyperglycemic and antioxidant activities of the extract of aerial yam (Dioscorea bulbifera)

This study investigated the anti-hyperglycemic and antioxidant activities of methanol extract of Dioscorea bulbifera with a view to studying the possibility of utilizing the yam in the management of hyperglycemia. Methanol extracts of the peels (MEPL), fresh (MEFL), and the whole tuber (MEWT) were prepared, phytochemically screened and assayed for α-amylase. Hyperglycemia was induced in rats using intraperitoneal injections of streptozotocin (40 mg/kg bwt) for five days, followed by administration of various doses of extract. Fasting blood sugar, alpha amylase, total protein, lipid profiles, creatinine, albumin, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured in plasma of test rats. The extracts were found to contain alkaloids, cardiac glycosides, carbohydrate, flavonoids, protein, saponins, tannins, triterpenoids and vitamin C and E. Preliminary assessment revealed that the whole tuber (MEWT) contained the highest levels of these phytochemicals and exhibited highest α-amylase inhibitory potential (47.54%, IC50 169.83 ± 18.64 μg/ml). Also, the extract possessed potent and concentration-dependent radical scavenging activities, comparable to that of the standard (Vitamin C). The extract also inhibited alpha amylase activity and caused significant improvement in elevated lipid profile and creatinine, comparable with that brought about by the standard drug Metformin. Histological examination of pancreatic section showed improved arrangement of islets of Langerhans in exocrine tissues of hyperglycemic groups treated with the extract when compared with hyperglycemic control. These results suggest that methanol extract of whole tubers possesses potent significant anti-hyperglycemic activity and that whole yam (without peeling) is appropriate for use in the management of hyperglycemia disorders. Key words: Dioscorea bulbifera, methanol extract, Streptozotozin, hyperglycemia, diabetes mellitus, antioxidants, lipid profile.

Chemical composition and in vitro antiobesity and in vivo anti-hyperlipidemic effects of Ceratotheca sesamoides, Jatropha tanjorensis, Mucuna flagellipes, Pterocarpus mildbraedii and Piper guineense

Ethnopharmacological relevanceCeratotheca sesamoides, Jatropha tanjorensis, Mucuna flagellipes, Pterocarpus mildbraedii and Piper guineense are all medicinal plants found in West Africa and used traditionally for the treatment of various ailments such as; hypertension, arteriosclerosis, anemia, malaria and flatulence. Aim of the studyThe purpose of this study is to ascertain the in vitro anti-obesity and in vivo anti-hyperlipidemic activity of extracts and fractions of selected plants. Materials and methodsThe ethanolic extract of the aforementioned five plants were tested in vitro for their activity against porcine pancreatic lipase and alpha-amylase at a concentration of 1mg/ml. Thereafter, the IC50 values of the plants active against alpha-amylase were determined. The ethanolic extract of P. mildbraedii and M. flagellipes were fractionated using n-hexane, n-butanol, ethyl acetate and water, thus the four fractions each obtained were used for further in vitro and in vivo studies. Thirty-five male rats were divided into seven groups out of which groups 2–7 were made hyperlipidemic using poloxamer 407 (1.0 g/kg body weight) intraperitoneally. Groups 1, 2 and 3 were the normal, hyperlipidemic and standard drug control groups respectively, whereas groups 4–7 were the test groups. ResultsC. sesamoides, M. flagellipes and P. mildbraedii inhibited alpha-amylase activity, while M. flagellipes and P. mildbraedii had activity against pancreatic lipase. The n-hexane fraction of P. mildbraedii and M. flagellipes inhibited both lipase and amylase enzyme activities among the four fractions of each plant tested. The GCMS analysis of n-hexane fractions revealed the presence of two major compounds in each plant which were 9-octadecenoic acid and hexadecanoic acid in P. mildbraedii, and hexadecanoic acid and 9,12-octadecadienoic acid in M. flagellipes. The in vivo studies revealed that the n-hexane fraction of P. mildbraedii and M. flagellipes significantly decreased (p < 0.05) total triglycerides, total cholesterol, and low density lipoprotein cholesterols when compared to the hyperlipidemic control rats. ConclusionsP. mildbraedii and M. flagellipes have the potency to act as antiobesity and anti-hyperlipidemic agents.

Yeast alpha glucosidase inhibitory and antioxidant activities of six medicinal plants collected in Phalaborwa, South Africa

Recent decades have experienced a sharp increase in the incidence and prevalence of diabetes mellitus. One antidiabetic therapeutic approach is to reduce gastrointestinal glucose production and absorption through the inhibition of carbohydrate-digesting enzymes such as α-amylase and α-glucosidase and α-amylase. The aim of the current study was to screen six medicinal plant species, with alleged antidiabetic properties for α-glucosidase inhibitory activities. Powdered plant materials were extracted with acetone, and tested for ability to inhibit baker's yeast α-glucosidase and α-amylase activities. The largest mass (440 mg from 10 g) of the extract was obtained from Cassia abbreviata, while both Senna italica and Mormordica balsamina yielded the lowest mass of the extracts. Extracts of stem bark of C. abbreviata inhibited baker's yeast α-glucosidase activity with an IC 50 of 0.6 mg/ml. This plant species had activity at low concentrations, with 1.0 mg/ml and above resulting in inhibition of over 70%. The other five plant extracts investigated had IC 50 values of between 1.8 and 3.0 mg/ml. Senna italica only managed to inhibit the activity of enzyme-glucosidase at high concentrations with an IC 50 value of 1.8 mg/ml, while Tinospora fragosa extracts resulted in about 55% inhibition of the activity of the enzyme at a concentration of 3.5 mg/ml, with an estimated IC 50 value of 2.8 mg/ml. The bark extract of C. abbreviata was the most active inhibitor of the enzyme, based on the IC 50 values (0.6 mg/ml). The bark extract of C. abbreviata contains non-competitive inhibitor(s) of α-glucosidase, reducing V max value of this enzyme from 5 mM·s –1 to 1.67 mM·s –1, while K m remained unchanged at 1.43 mM for para-nitrophenyl glucopyranoside. Antioxidant activity of the extracts was also investigated. The C. abbreviata extract was more active as an antioxidant than the positive control, trolox. The extracts did not inhibit alphaamylase activity more than about 20% at the highest concentration tested.

The Effect of Extruded Orange Pulp on Enzymatic Hydrolysis of Starch and Glucose Retardation Index

Orange pulp was extruded using a Brabender laboratory single screw extruder (20:1 L/D). The independent variables evaluated were barrel temperature (83, 100, 125, 150, and 167 °C), feed moisture content (22, 25, 30, 35, and 38/100 g), and screw speed (126, 140, 160, 180, and 194 rpm). The apparent density and apparent viscosity values of the extruded orange pulp increased during extrusion, while the oil absorption index decreased, in comparison with the values for raw orange pulp. In vitro studies showed that at the end of the incubation time, 90.68% of the starch was hydrolyzed in the control sample, while only 77.82% and 69.40% pulp of the starch experienced hydrolysis in the presence of raw fiber and extruded orange pulp, respectively. Extruded orange pulp showed a higher glucose retradation index (16.04–25.92%) after 30 min of dialysis and after 60 min (11.66% and 18.33%) than raw orange pulp (8.33%). These results indicated that glucose could be bound with compacted fiber matrices and inhibit alpha-amylase activity. These mechanisms may create a definite benefit by decreasing the rate of glucose absorption and eventually lowering the concentration of postprandial serum glucose. The potential hypoglycemic effects of extruded orange pulp suggest that orange pulp is a good and abundant dietary fiber resource that could be of great benefit in controlling glucose levels in the blood. It could also be added to high-fiber foods as a low-calorie bulk ingredient to reduce the calorie level.

Screening of traditional antidiabetic medicinal plants of mauritius for possible α‐amylase inhibitory effects in vitro

In this study, seven exotic/indigenous medicinal plants of Mauritius, namely Coix lacryma-jobi (Poaceae), Aegle marmelos (Rutaceae), Artocarpus heterophyllus (Moraceae), Vangueria madagascariensis (Rubiaceae), Azadirachta indica (Meliaceae), Eriobotrya japonica (Rosaceae) and Syzigium cumini (Myrtaceae) were studied for possible effects on starch breakdown by alpha-amylase in vitro. The results showed that only Artocarpus heterophyllus significantly (p < 0.05) inhibited alpha-amylase activity in vitro. To confirm the observed effects, a further biochemical assay was undertaken to investigate the effects of Artocarpus heterophyllus on alpha-amylase activity using rat plasma in vitro. It was found that the aqueous leaf extract significantly (p < 0.05) inhibited alpha-amylase activity in rat plasma. The highest inhibitory activity (27.20 +/- 5.00%) was observed at a concentration of 1000 microg/mL. However, in both cases dose dependency was not observed. Enzyme kinetic studies using the Michaelis-Menten and Lineweaver-Burk equations were performed to establish the type of inhibition involved. In the presence of the plant extract the maximal velocity (Vmax) remained constant (1/150 g / L/s) whereas the Michaelis-Menten constant (Km) increased by 5.79 g / L, indicating that the aqueous leaf extract of Artocarpus heterophyllus behaved as a competitive inhibitor. Results from the present study tend to indicate that Artocarpus heterophyllus could act as a 'starch blocker' thereby reducing post-prandial glucose peaks.

Biochemical study of the anti-diabetic action of the Egyptian plants Fenugreek and Balanites

Fenugreek and Balanites are two plants commonly used in Egyptian folk medicine as hypoglycemic agents. In the present study, the effects of 21 days oral administration of Fenugreek seed and Balanites fruit extracts (1.5 g/kg bw) on the liver and kidney glycogen content and on some key liver enzymes of carbohydrate metabolism in STZ-diabetic rats were studied. In addition, the effects of these two plant extracts on the intestinal alpha-amylase activity in vitro and starch digestion and absorption in vivo were also examined. Results indicated that single injection of STZ (50 mg/kg bw) caused 5-folds increase in the blood glucose level, 80% reduction in serum insulin level, 58% decrease in liver glycogen and 7-folds increase in kidney glycogen content as compared to the normal levels. The activity of glucose-6-phosphatase was markedly increased, whereas, the activities of both glucose-6-phosphate dehydrogenase and phospho-fructokinase were significantly decreased in the diabetic rat liver. Administration of Fenugreek extract to STZ-diabetic rats reduced blood glucose level by 58%, restored liver glycogen content and significantly decreased kidney glycogen as well as liver glucose-6-phosphatase activity. Meanwhile, Balanites extract reduced blood glucose level by 24% and significantly decreased liver glucose-6-phosphatase activity in diabetic rats. On the other hand, our results demonstrated that both the Fenugreek and Balanites extracts were able to in vitro inhibit alpha-amylase activity in dose-dependent manner. Fenugreek was more potent inhibitor than Balanites. This inhibition was reversed by increasing substrate concentration in a pattern which complies well with the effect of competitive inhibitors. Furthermore, this in vitro inhibition was confirmed by in vivo suppression of starch digestion and absorption induced by both plant extracts in normal rats. These findings suggest that the hypoglycemic effect of Fenugreek and Balanites is mediated through insulinomimetic effect as well as inhibition of intestinal alpha-amylase activity.

Anti-obesity action of Salix matsudana leaves (Part 2). Isolation of anti-obesity effectors from polyphenol fractions of Salix matsudana.

Previously, it was reported that polyphenol fractions prepared from the leaves of Salix matsudana reduced the elevation of the rat plasma triacylglycerol level at 3 and 4 h after oral administration of a lipid emulsion containing corn oil, at a dose of 570 mg/kg. Moreover, body weights at 2-9 weeks and the fi nal parametrial adipose tissue weights were significantly lower in mice fed the high-fat diet with 5% polyphenol fractions of S. matsudana leaves than in those fed the high-fat diet alone. The polyphenol fractions of S. matsudana leaves also significantly reduced the hepatic total cholesterol content, which was elevated in mice fed the high-fat diet alone. In addition, the polyphenol fractions of S. matsudana leaves inhibited palmitic acid uptake into brush border membrane vesicles prepared from rat jejunum and alpha-amylase activity, and their fractions enhanced norepinephrine-induced lipolysis in fat cells. To clarify the active substances inhibiting the palmitic acid uptake into small intestinal brush border membrane, the alpha-amylase activity or enhancing the norepinephrine-induced lipolyis in fat cells, the isolation of the active substances from polyphenol fraction was attempted using the above three assay systems. Compounds 1, 2 and 3 were isolated from the polyphenol fractions and identified as apigenin-7-O-d-glucoside, luteolin-7-O-d-glucoside and chrysoeriol-7-O-d-glucoside, respectively. Among three flavonoids, apigenin-7-O-d-glucoside inhibited alpha-amylase activity, and luteolin-7-O-d-glucoside and chrysoeriol-7-O-d-glucoside inhibited palmitic acid uptake into small intestinal brush border membrane. Furthermore, three flavonoid glucosides enhanced norepinephrine-induced lipolysis in fat cells.

Influence of tea catechins on the digestive tract

Tea catechins undergo various metabolic changes after they are taken orally, though a large percentage are excreted intact with the feces. Epidemiological studies suggest a protective effect of tea against various human cancers, including colon and rectum. The bactericidal property of tea catechins plays several roles in the digestive tract. In the small intestine, catechins inhibit alpha-amylase activity, and a certain amount is absorbed into the portal vein. Although catechins are bactericidal, they do not affect lactic acid bacteria. Including tea catechins in the diet for several weeks decreases putrefactive products and increases organic acids by lowering pH. These changes were achieved in tube-fed patients by administering 100 mg of tea catechins (equivalent to a cup of green tea) three times daily with meals for 3 weeks. When catechin administration ceased, the effects reversed after 1 week. Catechins should be considered further in colon carcinogenesis studies.

Effect of chemicals on fungal α-amylase activity

The effect of 8 growth regulators at concentrations of 1,000, 5,000 and 10,000 ppm on the activity of fungal (Aspergillus flavus var. columnaris) alpha-amylase was studied. Indol acetic acid (IAA) and naphthalene acetic acid (NAA) inhibited alpha-amylase activity by 2% and 7% at 1,000 ppm. The other 6 growth regulators, indol butyric acid (IBA), gibberellic acid, cumarin, cycocel (CCC), atonik-G and kylar, did not inhibit but stimulated alpha-amylase activity (0 to 9%) at 1,000 ppm. All growth regulators studied inhibited alpha-amylase activity at 5,000 and 10,000 ppm concentration except kylar. The effect of organic acids and formaldehyde at 0.01, 0.005, and 0.001 M was studied. Acetic acid stimulated alpha-amylase at all concentrations, but formic acid, oxalic acid, lactic acid and citric acid inhibited alpha-amylase activity by 91, 100, 100 and 79%, respectively, at a concentration of 0.01 M, while by 31, 100, 15 and 20%, respectively, at 0.005 M. Formaldehyde induced 7, 3 and 2% inhibition at 0.01, 0.005 and 0.001 M, respectively. At 0.01 M either sorbitol or fructose inhibited alpha-amylase by 8%, Maltose 7%, sucrose 6%, phenol, glucose and galactose each by 5%, ethanol, glycerol, arabinose and sodium benzoate each by 4%, isopropanol and mannitol 1%, but methanol and ammonium citrate dibasic did not inhibit alpha-amylase. The results indicate that CuCl2, SnCl2, AgNO3 and Fe2(SO4)3 were the strongest inhibitors, followed by Cd(C2H3O2), HgCl2, Na2-EDTA, Na2HPO4, and CaCl2 in decreasing order. NaCl, NaBr and Mn SO4 did not inhibit alpha-amylase at concentrations from 10 mM to 0.01 mM.

Bacterial Alpha-Amylase Inhibitors

Summary The effect of 5 growth regulators at concentrations of 50, 100, and 1000 ppm on the activity of B. subtilis-37 alpha-amylase was studied. Indol butyric acid (IBA) did not inhibit alpha-amylase activity at concentrations of 50 to 1000 ppm. The other 4 growth regulators, 6-furfurylamino-purine, gibberellic acid, naphthalene acetic acid, and atonik-G, at all concentrations inhibited alpha-amylase activity. The effect of organic acids and formaldehyde at 0.01 M, 0.001 M, and 0.0005 M was studied. Acetic acid, oxalic acid, lactic acid, and malic acid at 0.01 M and 0.001 M caused 100 % inhibition of alpha-amylase, but at 0.0005 M the inhibitions were 14 %, 46 %, 12%, and 28%, respectively. Tartaric acid induced 100%, 85%, and 62% inhibition for alphaamylase at 0.01, 0.001, and 0.0005 M, respectively, but at the same concentration formaldehyde caused 60 %, 53 %, and 51 % inhibition. At 0.01 M concentration isopropanol, glycerol, and mannitol did not inhibit alpha-amylase activity. The inhibition percentages, caused by phenol, arabinose, lactose, maltose, galactose, ethanol, and sodium benzoate, were 13, 10, 8, 6, 6.5, and 4. Sorbitol, glucose, and fructose caused 3 % inhibition, while it was 2 % by sucrose at 0.01 M. But ammonium citrate dibasic at 0.01 M induced 60% inhibition for alpha-amylase activity. It was found that ZnSO4 and Fe2(SO4)3 were the strongest inhibitors, followed by SnCl2, Pb(C2H3O2)2, AgNO3, AlCl3, Cd(C2H3O2), CuCl2, FeSO4, HgCl2, and Na2-EDTA, in decreasing order. MnSO4 was a moderate inhibitor. The slight inhibitors in decreasing order were BaCl2, Co(NO3)2, Na2HPO4, NiSO4, and finally MgCl2.