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(-)-Epigallocatechin gallate (EGCG), the chief dietary constituent in green tea ( Camellia sinensis ), is relatively unstable under oxidative conditions. This study evaluated the use of non-thermal dielectric barrier discharge (DBD) plasma to improve the anti-digestive enzyme capacities of EGCG oxidation products. Pure EGCG was dissolved in an aqueous solution and irradiated with DBD plasma for 20, 40, and 60 min. The reactant, irradiated for 60 min, exhibited improved inhibitory properties against α-glucosidase and α-amylase compared with the parent EGCG. The chemical structures of these oxidation products 1 - 3 from the EGCG, irradiated with the plasma for 60 min, were characterized using spectroscopic methods. Among the oxidation products, EGCG quinone dimer A ( 1 ) showed the most potent inhibitory effects toward α-glucosidase and α-amylase with IC 50 values of 15.9 ± 0.3 and 18.7 ± 0.3 μM, respectively. These values were significantly higher than that of the positive control, acarbose. Compound 1 , which was the most active, was the most abundant in the plasma-irradiated reactant for 60 min according to quantitative high-performance liquid chromatography analysis. These results suggest that the increased biological capacity of EGCG can be attributed to the structural changes to EGCG in H 2 O, induced by cold plasma irradiation.

The present paper reports the determination of the activation energies and the optimum temperatures of starch hydrolysis by porcine pancreas α -amylase. The parameters were estimated based on the literature data on the activity curves versus temperature for starch hydrolysis by α-amylase from porcine pancreas. It was assumed that both the hydrolysis reaction process and the deactivation process of α -amylase were first-order reactions by the enzyme concentration. A mathematical model describing the effect of temperature on porcine pancreas α -amylase activity was used. The determine deactivation energies E a were from 19.82 ± 7.22 kJ/mol to 128.80 ± 9.27 kJ/mol, the obtained optimum temperatures T opt were in the range from 311.06 ± 1.10 K to 326.52 ± 1.75 K. In turn, the values of deactivation energies E d has been noted in the range from 123.57 ± 14.17 kJ/mol to 209.37 ± 5.17 kJ/mol. The present study is related to the starch hydrolysis by α -amylase. In the industry, the obtained results the values E a , E d , T opt can be used to design and optimize starch hydrolysis by α -amylase porcine pancreas. The obtained results might also find application in research on the pharmaceutical preparations used to treat pancreatic insufficiency or prognosis of pancreatic cancer.

<b>Background and Objective:</b> Cardiovascular Diseases (CVDs) remain the main cause of mortality globally. High cholesterol levels (hypercholesterolemia) and high blood glucose (diabetes) are among the factors that increase the risk for CVDs. Application of inhibitors for the digestive enzymes accountable for the macronutrient hydrolysis, such as carbohydrates and fats, is one of the prevalent approaches in the development of medications against CVDs. The present study was performed to examine, <i>in vitro</i>, the lipase and amylase inhibitory potential of phenolic rich extract of leaves of four date palm cultivars. <b>Materials and Methods:</b> In the current study, the research investigated the potentiality of phytochemicals extracted from leaves of four date palm cultivars (Rawthan, Rabeaa, Barny and Ajwa), collected from Al-Madinah Governorate as lipase and amylase inhibitors and as antioxidants. Moreover, the total contents of flavonoids and phenolics were assessed. <b>Results:</b> The results revealed that all the tested cultivars showed promising lipase and amylase inhibition and antioxidants capacities. However, Rawthan and Ajwa were the most powerful cultivars. <b>Conclusion:</b> Therefore, the results presented herein suggest as the earliest report, the potential use of date palm leaves as a potential source for lipase and amylase inhibitors as an approach to decrease the risk for CVDs.

An acidic tea polysaccharide (TPSA) isolated from green tea was fractionated using a precipitation-fractionation method into seven fractions with different molecular weights. TPSA was characterized as a hyperbranched polysaccharide with a globular homogeneous conformation by analysis of solution parameters of each fraction using static light scattering and viscosity analyses. Observation by transmission electron microscopy confirmed that TPSA occurred as globular homogeneous particles with size in the range of 20-40 nm. To simulate the branched chain segments of TPSA, four model molecules were designed based on chemical structure of TPSA. Molecular docking analysis indicated that the branched chain segments of TPSA similar to the TPSA-4 model molecule showed preferential binding to α-amylase to form the TPSA/α-amylase complex through hydrogen bonding interactions. Circular dichroism spectroscopy showed that the structure of α-amylase was not significantly affected by TPSA. The mechanism of α-amylase inhibitory activity of TPSA was simulated by molecular docking analysis. The branched chain segments of TPSA similar to the TPSA-4 model molecule likely act as a potential competitor to the starch substrate to inhibit the activity of α-amylase., Competing Interests: Declaration of competing interest Authors declare that they have no competing financial interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

This study sought to evaluate the effects of Phaseolus multiflorus var. albus Bailey extract (PM extract) and Pleurotus eryngii var. ferulae extract (PF extract) on the inhibition of digestive enzymes and to confirm the anti-obesity effect of DKB-117 (a mixture of PM extract and PF extract) in digestive enzyme inhibition in a mouse model of obesity induced by a high-fat diet. In in vitro studies, PM extract and PF extract have increased dose-dependent inhibitory activity on α- amylase (Inhibitory concentration (IC 50 value: 6.13 mg/mL)) and pancreatic lipase (IC 50 value; 1.68 mg/mL), respectively. High-fat diet-induced obese mice were orally administered DKB-117 extracts at concentrations of 100, 200, and 300 mg/kg/day, while a positive control group was given orlistat (pancreatic lipase inhibitor) and Garcinia cambogia (inhibiting the enzymes needed to synthesize carbohydrates into fat) at concentrations of 40 and 200 mg/kg/day, respectively, for eight weeks. As a result, body weight, fat mass (total fat mass, abdominal fat, and subcutaneous fat) detected with microcomputed tomography, fat mass (abdominal fat and inguinal fat) after an autopsy, and liver triglyceride levels were decreased significantly in the DKB-117 (300 mg/kg/day) group compared to those in the HFD control group. Additionally, we obtained results indicating that the presence of carbohydrates was found more in the DKB-117-300 (300 mg/kg/day) group than in the HFD control group. These data clearly show that DKB-117 extracts are expected to have an anti-obesity effect through a complex mechanism that promotes carbohydrate release through the inhibition of carbohydrate-degrading enzymes while blocking lipid absorption through lipase inhibition.

The leaves and fruits of Rhus coriaria are traditionally used in Turkey for the treatment of diabetes. The aim of the present study is to determine α-amylase, α-glucosidase, and pancreatic lipase inhibitory activities of R. coriaria leaf and fruit ethanol extracts (80%), and to isolate active compounds against these enzymes. As a result of the activity-guided isolation, the active compounds were determined as the amentoflavone, agathisflavone, and 1,2,3,4,6-penta-O-galloyl-β-glucopyranose. Agathisflavone, amentoflavone, and penta-O-galloyl-β-glucopyranose inhibited α-glucosidase with 11.4 ± 0.9, 11.3 ± 0.7, and 4.1 ± 0.1 µM IC 50 values, respectively. Furthermore, penta-O-galloyl-β-glucopyranose inhibited α-amylase with 6.32 ± 0.18 µM IC 50 . These three compounds also significantly inhibited (P < 0.05) pancreatic lipase. The results of high-performance liquid chromatography analysis showed that penta-O-galloyl-β-D-glycopyranose was one of the main compounds in both fruit and leaf extracts. Therefore, it may be considered that R. coriaria fruit and leaf extracts can be standardized on this substance and used in the development of both medicinal products and functional food for diabetes. PRACTICAL APPLICATION: Rhus coriaria (Sumac) is one of the plants that is well known and used around the world as a spice. It is also used against diabetes traditionally. The determination of effective compounds can lead to the standardization and development of both medicinal products and functional foods for diabetes. While the fruits of the plant are used as a spice all around the world, the leaves are generally throw away; therefore, the usage of the leaves to the food and medical industry can lead to beneficial effects on the economy., (© 2020 Institute of Food Technologists®.)

This study reported simultaneously improved thermostability and hydrolytic pattern of α-amylase from Bacillus subtilis CN7 by rationally engineering the mostly conserved central beta strands in TIM barrel fold. Nine single point mutations and a double mutation were introduced at the 2nd site of the β7 strand and 3rd site of the β5 strand to rationalize the weak interactions in the beta strands of the TIM barrel of α-amylase. All the five active mutants changed the compositions and percentages of maltooligosaccharides in final hydrolytic products compared to the product spectrum of the wild-type. A mutant Y204V produced only maltose, maltotriose, and maltopentaose without any glucose and maltotetraose, indicating a conversion from typical endo-amylase to novel maltooligosaccharide-producing amylase. A mutant V260I enhanced the thermal stability by 7.1 °C. To our best knowledge, this is the first report on the simultaneous improvement of thermostability and hydrolytic pattern of α-amylase by engineering central beta strands of TIM barrel and the novel "beta strands" strategy proposed here may be useful for the protein engineering of other TIM barrel proteins.

A series of novel isoxazolidines based on benzaldehyde derivatives have been synthesized from the cycloaddition of chiral menthone-based nitrone and allyl phenyl ethers. All synthetic compounds were assessed for their in vitro PPA, HPA and HLAG inhibitory activity. The results revealed that all targets exhibited better inhibitory effect against PPA (12.3 ± 0.4 < IC 50  < 38.2 ± 0.9 μM), HPA (10.1 ± 0.4 < IC 50  < 26.8 ± 0.2 μM) and HLAG (65.4 ± 1.2 < IC 50  < 274.8 ± 1.1 μM) when compared with the reference inhibitor, acarbose (IC 50  = 284.6 ± 0.3 μM for PPA, 296.6 ± 0.8 μM for HPA, 780.4 ± 0.3 μM for HLAG) with the highest PPA inhibitory activity was ascribed to compound 3g against both PPA and HPA, and 3b against HLAG enzymes, respectively. Structural activity relationships (SARs) were also established for all synthesized compounds and the interaction modes of the most potent inhibitors (3g for PPA and HPA, 3b for HLAG) and the active site with residues of three enzymes were confirmed through molecular docking studies. Furthermore, a combination of molecular docking analysis with the in vitro activities can help to improve prediction success and encourages the uses of some of these molecules as potential alternatives toward the modulation of T2D., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

In this study, we investigated the structural characterization and antidiabetic effects of Lactobacillus H31 exopolysaccharide (EPS) H31-2 from pickled cabbage. The BLAST result indicated that Lactobacillus H31 was closely related to Lactobacillusplantarum S1S2L2. In the spectrum of Fourier-transform infrared spectroscopy (FT-IR), 3370 cm -1 was the characteristic band of polysaccharide. A structural analysis showed that the monosaccharides of EPS H31-2 included d-mannose (Man) and d-glucose (Glc). The molecular weight of EPS H31-2 was around 10.75 kDa. All these results suggested EPS H31-2 was a novel polysaccharide. The inhibition ratios of crude EPS H31 and the pure fraction H31-2 of pancreatic α-amylase were 89.1 ± 2.59% and 69.2 ± 8.95%, respectively. In addition, the supernatant glucose concentration of insulin-resistant HepG2 cells decreased by treatment with 10 -8 M of EPS H31-2, which meant EPS H31-2 could promote the glucose uptake of insulin-resistant HepG2 cell. Furthermore, EPS H31-2 upregulated the expression of the GLUT-4, Akt-2, and AMPK, which play important roles in glycometabolism. These results suggested that Lactobacillus plantarum EPS H31-2 could effectively inhibit the activity of pancreas α-amylase and has potential applications in the prevention and alleviation of diabetes mellitus., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Starch digestion in the small intestines of the dairy cow is low, to a large extent, due to a shortage of syntheses of α-amylase. One strategy to improve the situation is to enhance the synthesis of α-amylase. The mammalian target of rapamycin (mTOR) signalling pathway, which acts as a central regulator of protein synthesis, can be activated by leucine. Our objectives were to investigate the effects of leucine on the mTOR signalling pathway and to define the associations between these signalling activities and the synthesis of pancreatic enzymes using an in vitro model of cultured Holstein dairy calf pancreatic tissue. The pancreatic tissue was incubated in culture medium containing l-leucine for 3 h, and samples were collected hourly, with the control being included but not containing l-leucine. The leucine supplementation increased α-amylase and trypsin activities and the messenger RNA expression of their coding genes (P <0.05), and it enhanced the mTOR synthesis and the phosphorylation of mTOR, ribosomal protein S6 kinase 1 and eukaryotic initiation factor 4E-binding protein 1 (P <0.05). In addition, rapamycin inhibited the mTOR signal pathway factors during leucine treatment. In sum, the leucine regulates α-amylase and trypsin synthesis in dairy calves through the regulation of the mTOR signal pathways.

This study aimed to investigate the effects of isoleucine (Ile) on the synthesis and secretion of digestive enzymes and cellular signalling in the pancreatic tissue of dairy goats. The pancreatic tissues were incubated in buffer containing 0, 0.40, 0.80, and 1.60 mM Ile. High levels of Ile significantly increased the buffer release and total concentration of ɑ -amylase in the tissues (P < 0.001). The total trypsin and chymotrypsin concentrations in each of the Ile groups were significantly higher than those in the control group (P < 0.05); however, lipase was not affected. High levels of Ile significantly increased ɑ -amylase mRNA expression (P < 0.001) but had no effect on the mRNA expression of trypsin, chymotrypsin, or lipase. Ile did not affect S6K1 phosphorylation levels. High levels of Ile significantly increased the expression of the γ isoform of 4EBP1 (P < 0.001), which indicated that the phosphorylation of 4EBP1 was significantly increased. The phosphorylation level of eEF2 gradually decreased with the addition of Ile (P < 0.001). These results suggested that high doses of Ile can regulate the excretion of enzymes, especially ɑ -amylase, in the pancreatic tissues of dairy goats by modulating mTOR signalling, and this regulation is independent of the mTOR-S6K1 pathway.

Less-common fruits from Cornus spp. (Cornaceae), also named dogwoods, have shown antidiabetic, antibacterial and anti-allergic properties and are thus considered a source of phytochemicals that are beneficial to human health. The study aimed to compare the chemical compositions of the aqueous and ethanolic extracts of lyophilized fresh-picked and commercially available dried fruits of Cornus mas (Cm, cornelian cherry) and Cornus alba (Ca) fruits using HPLC-DAD-MS/MS method. Simultaneously, the α-amylase and pancreatic lipase (PL) inhibitory activities of the prepared extracts were compared by in vitro fluorescence assay based on the kinetic hydrolysis of starch or oleate ester of 4-methylumbelliferone (MUO), respectively. Additionally, a bio-assay guided identification of compounds potentially responsible for the inhibition of pancreatic enzymes was performed. Iridoids (loganic acid, cornuside) and anthocyanins (pelargonidin 3-O-galactoside) were identified in the Cm fruit extracts. Flavonoids, such as quercetin and kaempferol derivatives, were detected in the Ca fruit extracts. The chromatographic separation of the constituents of Ca fruit provided a fraction containing phenolic acids derivatives, which inhibited PL activity by 69.9 ± 4.5% at a concentration of 7.5 μg·mL -1 . The IC 50 of hydroxytyrosol glucoside, isolated from the most active Ca fraction, was 0.99 ± 0.10 mg·mL -1 indicating other constituents responsible for the fraction activity. The most active subfraction from Cm fruit (7.5 μg·mL -1 ), which inhibited PL activity by 28.3 ± 1.5%, contained pelargonidin 3-O-galactoside. Loganic acid and cornuside in highly pure form did not inhibit lipase activity. The phytochemical constituents of Cm, and particularly of Ca fruit extracts, can inhibit pancreatic enzymes and thus might be considered effective preparations in the prevention and control of hyperlipidemia related diseases., (Copyright © 2018. Published by Elsevier Taiwan LLC.)

Pancreatic α-amylase plays an important role in dietary starch hydrolysis in the small intestine and participates in enhanced glucose concentration after meals. It seems to be a problem for diabetic patients, who suffer from longer postprandial hyperglycemia after meal consumption than healthy people. There are commercially available drugs that inhibit α-amylase and thus reduce the postprandial hyperglycemia effect. However, these drugs may cause severe side effects. Conversely, some naturally occurring flavonoids were suggested to have an α-amylase-inhibiting effect without any side effects. There had been no rapid, undemanding method in terms of sample and reagent preparation that would enable screening of many potential inhibitors. Therefore, we developed an online capillary electrophoresis method to monitor α-amylase activity in the presence of an inhibitor. Each reaction constituent was introduced separately, directly into a capillary where the reagents were mixed by diffusion, which resulted in a 5-min analysis including conditioning of the capillary. We applied the method to test the inhibitory effect of flavonoid standards and their mixture and we investigated the inhibitory effect of ethanolic extract from Betula pendula bark. The developed method presents a faster and less expensive alternative to previously described offline methods. Graphical abstract Online CE screening of α-amylase inhibitors.

Objective: The current study was designed to evaluate the various antioxidant potentials and inhibitory effects of phenolic-rich leaf extracts of Bridelia ferruginea (BF) on the in vitro activities of some key enzymes involved in the metabolism of carbohydrates., Methods: In this study, BF leaf free and bound phenolic-rich extracts were used. We quantified total phenolic and flavonoid contents, and evaluated several antioxidant activities using assays for ferric reducing antioxidant power, total antioxidant activity (phosphomolybdenum reducing ability), 1,1-diphenyl-2-picrylhydrazyl and thiobarbituric acid reactive species. Also, extracts were tested for their ability to inhibit α-amylase and α-glucosidase activity., Results: The total phenolic and total flavonoid contents in the free phenolic extract of BF were significantly greater than in the bound phenolic extract. Also, all the antioxidant activities considered were significantly greater in the free phenolic extract than in the bound phenolic extract. In the same vein, the free phenolic-rich extract had a significantly higher percentage inhibition against α-glucosidase activity (IC 50  = 28.5 µg/mL) than the bound phenolic extract (IC 50  = 340.0 µg/mL). On the contrary, the free phenolic extract (IC 50  = 210.0 µg/mL) had significantly lower inhibition against α-amylase than the bound phenolic-rich extract (IC 50  = 190.0 µg/mL)., Conclusion: The phenolic-rich extracts of BF leaves showed antioxidant potentials and inhibited two key carbohydrate-metabolizing enzymes in vitro., (Copyright © 2018 Shanghai Changhai Hospital. Published by Elsevier B.V. All rights reserved.)

Ethnopharmacological Relevance: Plants preparations are used by traditional medicine in the treatment of various diseases, such as type-2 diabetes mellitus. Some medicinal plants are capable of controlling the complications of this metabolic disease at different levels, for example, providing antioxidant compounds that act against oxidative stress and protein glycation and others which are capable of inhibiting the catalysis of digestive enzymes and thus contribute to the reduction of hyperglycemia and hyperlipidemia. Our objective was to investigate the antioxidant and anti-glycation activities of some medicinal plants and their potential inhibitory against α-amylase, α-glucosidase and pancreatic lipase activities., Material and Methods: Based on the ethnobotanical researches carried out by academic studies conducted at the Federal University of Uberlandia, ten plants traditionally used in the treatment of type-2 diabetes mellitus were selected. Ethanol (EtOH) and hexane (Hex) extracts of specific parts of these plants were used in enzymatic assays to evaluate their inhibitory potential against α-amylase, α-glucosidase and lipase, as well as their antioxidant (DPPH, ORAC and FRAP) and anti-glycation (BSA/fructose model) capacities., Results: The results indicate that EtOH extract of four of the ten analyzed plants exhibited more than 70% of antioxidant and anti-glycation capacities, and α-amylase and lipase inhibitory activities; no extract was able to inhibit more than 40% the α-glucosidase activity. The EtOH extracts of Bauhinia forficata and Syzygium. cumini inhibited α-amylase (IC 50 8.17 ± 2.24 and 401.8 ± 14.7 μg/mL, respectively), whereas EtOH extracts of B. forficata, Chamomilla recutita and Echinodorus grandiflorus inhibited lipase (IC 50 59.6 ± 10.8, 264.2 ± 87.2 and 115.8 ± 57.1 μg/mL, respectively). In addition, EtOH extracts of B. forficata, S. cumini, C. recutita and E. grandiflorus showed, respectively, higher antioxidant capacity (DPPH IC 50 0.7 ± 0.1, 2.5 ± 0.2, 1.3 ± 0.2 and 35.3 ± 9.0 μg/mL) and anti-glycation activity (IC 50 22.7 ± 4.4, 246.2 ± 81.7, 18.5 ± 2.8 and 339.0 ± 91.0 μg/mL)., Conclusions: EtOH extracts of four of the ten species popularly cited for treatment of type 2 diabetes mellitus have shown promising antioxidant and anti-glycation properties, as well as the ability to inhibit the digestive enzymes α-amylase and lipase. Thus, our results open new possibilities for further studies in order to evaluate the antidiabetic potential of these medicinal plants., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Context: Pancreatic α-amylase and α-glucosidase inhibitors serve as important strategies in the management of blood glucose. Even though Syzygium cumini (L.) Skeels (Myrtaceae) (SC) is used extensively to treat diabetes; scientific evidence on antidiabetic effects of SC leaves is scarce., Objective: SC leaf extract was investigated for α-amylase inhibitory effect and continued with isolation and identification of α-amylase inhibitors., Materials and Methods: Bioassay-guided fractionation was conducted using in vitro α-amylase inhibitory assay (with 20-1000 μg/mL test material) to isolate the inhibitory compounds from ethyl acetate extract of SC leaves. Structures of the isolated inhibitory compounds were elucidated using 1 H NMR and 13 C NMR spectroscopic analysis and direct TLC and HPLC comparison with authentic samples. Study period was from October 2013 to October 2015., Results: An active fraction obtained with chromatographic separation of the extract inhibited porcine pancreatic α-amylase with an IC 50 of 39.9 μg/mL. Furthermore, it showed a strong inhibition on α-glucosidase with an IC 50 of 28.2 μg/mL. The active fraction was determined to be a 3:1 mixture of ursolic acid and oleanolic acid. Pure ursolic acid and oleanolic acid showed IC 50 values of 6.7 and 57.4 μg/mL, respectively, against α-amylase and 3.1 and 44.1 μg/mL respectively, against α-glucosidase., Discussion and Conclusions: The present study revealed strong α-amylase and α-glucosidase inhibitory effects of ursolic acid and oleanolic acid isolated from SC leaves for the first time validating the use of SC leaves in antidiabetic therapy.

Context: Adiantum capillus-veneris L. (Adiantaceae) hypocholesterolemic activity is therapeutically praised., Objectives: Pharmacological modulation of pancreatic triacylglycerol lipase (PL) and α-amylase/α-glucosidase by A. capillus-veneris are evaluated., Materials and Methods: Using positive controls (acarbose, orlistat, guar gum, atorvastatin, glipizide and metformin) as appropriate, crude aqueous extracts (AEs) of A. capillus-veneris aerial parts were tested via a combination of in vitro enzymatic (0.24-100 mg/mL), acute in vivo carbohydrate tolerance tests (125, 250 or 500 mg/kg body weight [b.wt]) and chronic in vivo studies (500 mg/kg b.wt) in high cholesterol diet (HCD) fed Wistar rats., Results: Like acarbose, A. capillus-veneris as well as chlorogenic acid, with respective IC 50 values (mg/mL) of 0.8 ± 0.0 and 0.2 ± 0.0, were identified as in vitro potent dual inhibitors of α-amylase/α-glucosidase. Unlike guar gum, A. capillus-veneris had no glucose diffusion hindrance capacity. Equivalent to orlistat, A. capillus-veneris and its phytoconstituents inhibited PL in vitro with an ascending order of PL- IC 50 values (μg/mL): ferulic acid; 0.48 ± 0.06 < ellagic acid; 13.53 ± 1.83 < chlorogenic acid; 38.4 ± 2.8 < A. capillus-veneris; 1600 ± 100. Incomparable to acarbose or metformin and glipizide, A. capillus-veneris (125, 250 and 500 mg/kg b.wt) lacked antihyperglycaemic efficacies in acute starch- or glucose-evoked postprandial hyperglycaemia increments in normoglycaemic overnight fasting rats. Superior to atorvastatin; A. capillus-veneris exerted significant antiobesity (p < 0.001) with marked triacylglycerol-reducing capacities (p < 0.001) in comparison to rats fed with HCD for 10 weeks., Discussion and Conclusion: A. capillus-veneris, modulating pancreatic digestive enzymes, may be advocated as a combinatorial diabesity prevention/phytotherapy agent.

Context: The use of Aframomum melegueta K. Schum. (Zingiberaceae) fruit for treatment of diabetes has recently been established in Nigeria. However, compounds responsible for the antidiabetic action have not been identified., Objective: The present study carried out the bioassay-guided isolation of possible bioactive compounds responsible for the antidiabetic action of A. melegueta fruit., Materials and Methods: The A. melegueta fruit was sequentially extracted using ethyl acetate (EtOAc), ethanol and water, and the most active extract (EtOAc) was subjected to column chromatography on a silica gel column using solvent gradient systems of hexane (HEX):EtOAc and EtOAc:MeOH and the isolation of compounds was guided by α-glycosidase and α-amylase inhibitory activities at various concentrations (30-240 μg/mL)., Results: According to the results, 3 arylalkanes, 6-paradol (1), 6-shogaol (2) and 6-gingerol (3) and a pentacyclic triterpene, oleanolic acid (4) were isolated from A. melegueta fruit. All the compounds exhibited inhibitory effects against α-amylase and α-glucosidase. 6-Gingerol (3) and oleanolic acid (4) showed higher inhibitory activity against α-amylase (IC 50 : 6-gingerol: 81.78 ± 7.79 μM; oleanolic acid: 91.72 ± 1.63 μM) and α-glucosidase (IC 50 : 6-gingerol: 21.55 ± 0.45 μM; oleanolic acid: 17.35 ± 0.88 μM) compared to the standard drug, acarbose and other isolated compounds. The kinetics of the enzyme action of the compounds showed a noncompetitive mode of inhibition., Conclusion: The data of this study suggest that the 6-gingerol (3) and oleanolic acid (4) showed higher α-amylase and α-glucosidase inhibitory action and therefore could be responsible for the antidiabetic activity of A. melegueta fruit.

The studies presented were designed to highlight the impact of pancreatic enzymes on glycemic control and insulin response. Blood glucose and plasma insulin levels were monitored after intravenous, oral or direct gut glucose tolerance tests (GTT) in 6 pigs with an intact gastrointestinal tract and in 12 pigs following duodenal-jejunal bypass (DJB) surgery. In the intact pigs, pancreatic enzymes (Creon®) given orally 1 h prior to the GTT, lowered the blood glucose levels during the oral and meal GTT and reduced the plasma insulin response during the intravenous and meal GTT. In DJB pigs, blood glucose and plasma insulin levels were higher following glucose loading into the by-passed biliopancreatic limb as compared to that following glucose loading orally or into the common intestinal limb. Infusion of amylase or amylase peptides together with glucose into the biliopancreatic limb lowered blood glucose levels in DJB pigs. These preliminary data suggest new, extra-digestive, actions of enteral pancreatic enzymes - probably amylase or its peptides - on glucose homeostasis, with an reduction in net glucose absorption into the blood and in insulin response. This ability of digestive enzymes (amylase) to reduce post-prandial hyperglycaemia in an insulin-independent manner could aid in preventing the development of obesity and diabetes.

To understand the mechanism responsible for the α-amylase inhibitory activity of tea polysaccharides, the interaction between α-amylase and an acidic branched tea polysaccharide (TPSA) was investigated using fluorescence spectroscopy and resonance light scattering analysis. TPSA, exhibiting inhibitory activity towards α-amylase (the maximum inhibition percentage of 65%), was isolated from green tea (Camellia sinensis) and characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and gas chromatography. Synchronous fluorescence spectroscopy revealed that the binding interaction between the tryptophan residues of α-amylase and TPSA was predominant. Based on the fluorescence quenching effect of tryptophan residues induced by TPSA, the binding constants between α-amylase and TPSA were determined to be 18.6×10 6 , 8.0×10 6 and 4.6×10 6 L·mol -1 at 20, 30 and 37°C, respectively. The calculated Gibbs free-energy changes were negative, indicating that the bonding interaction was a spontaneous process. The enthalpy and the entropy changes were -62.13 KJ·mol -1 and -0.0728 KJ·mol -1 ·K -1 , suggesting that hydrogen bonding interactions might play a major role in the binding process. The formation of an α-amylase/TPSA complex was evidenced by fluorescence quenching and resonance light scattering analysis, and this complex could be the main contributor to the α-amylase inhibitory activity of TPSA., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The potential of the modified magnetic nanoparticles for covalent immobilization of porcine pancreatic α-amylase has been investigated. The synthesis and immobilization processes were simple and fast. The co-precipitation method was used for synthesis of magnetic iron oxide (Fe 3 O 4 ) nanoparticles (NPs) which were subsequently coated with silica through sol-gel reaction. The amino-functionalized NPs were prepared by treating silica-coated NPs with 3-aminopropyltriethoxysilane followed by covalent immobilization of α-amylase by glutaraldehyde. The optimum enzyme concentration and incubation time for immobilization reaction were 150 mg and 4 h, respectively. Upon this immobilization, the α-amylase retained more than 50 % of its initial specific activity. The optimum pH for maximal catalytic activity of the immobilized enzyme was 6.5 at 45 °C. The kinetic studies on the immobilized enzyme and its free counterpart revealed an acceptable change of K m and V max . The Km values were found as 4 and 2.5 mM for free and immobilized enzymes, respectively. The V max values for the free and immobilized enzymes were calculated as 1.75 and 1.03 μmol mg -1  min -1 , in order, when starch was used as the substrate. A quick separation of immobilized amylase from reaction mixture was achieved when a magnetically active support was applied. In comparison to the free enzyme, the immobilized enzyme was thermally stable and was reusable for 9 cycles while retaining 68 % of its initial activity.

Starch provides the major source of caloric intake in many diets. Cleavage of starch into malto-oligosaccharides in the gut is catalyzed by pancreatic α-amylase. These oligosaccharides are then further cleaved by gut wall α-glucosidases to release glucose, which is absorbed into the bloodstream. Potential surface binding sites for starch on the pancreatic amylase, distinct from the active site of the amylase, have been identified through X-ray crystallographic analyses. The role of these sites in the degradation of both starch granules and soluble starch was probed by the generation of a series of surface variants modified at each site to disrupt binding. Kinetic analysis of the binding and/or cleavage of substrates ranging from simple maltotriosides to soluble starch and insoluble starch granules has allowed evaluation of the potential role of each such surface site. In this way, two key surface binding sites, on the same face as the active site, are identified. One site, containing a pair of aromatic residues, is responsible for attachment to starch granules, while a second site featuring a tryptophan residue around which a malto-oligosaccharide wraps is shown to heavily influence soluble starch binding and hydrolysis. These studies provide insights into the mechanisms by which enzymes tackle the degradation of largely insoluble polymers and also present some new approaches to the interrogation of the binding sites involved.

To find new, plant based drugs for the treatment of obesity and/or diabetes mellitus type 2 through the inhibition of essential digestive enzymes, in vitro tests were carried out on selected plants or fungi with weight-reducing, blood glucose-reducing or related potential, used in Traditional Chinese Medicine (TCM). Aqueous and methanolic extracts of 32 Chinese herbal medicines were assayed for their in vitro inhibitory activity against pancreatic lipase (PL) and α-amylase (PA). PL activity was measured by using an enzymatic in vitro assay based on the hydrolysis kinetics of an oleate ester of 4-methylumbelliferone. For the determination of α-amylase activity an enzyme assay based on the hydrolytic cleavage of a modified starch derivative was used. Our findings have shown that the methanolic extract of Lycopus lucidus Turcz. var. hirtus Regel (Lamiaceae) was a very effective PL inhibitor (IC50: 88.3±4.1 μg/mL). A high anti-amylase activity showed the methanolic extract of Trichosanthes kirilowii Maxim. (Curcurbitaceae, IC50: 248.8±67.3 μg/mL). This work provides a priority list of interesting plants for further study with respect to the treatment of obesity and associated metabolic diseases.

A high throughput assay was applied to guide the isolation of a new pancreatic α-amylase inhibitor, dracoflavan B, from the dragon's blood resin from Daemonorops draco. Applying C18 column, we successfully isolated both diastereomers and their structures verified by (1)H NMR spectra in comparison with the literature values. Their activity in inhibition of pancreatic α-amylase with comparable IC50 values of 23μM (A type) and 27μM (B type) that are similar to that of acarbose. Dracoflavan B shows much weaker activity in inhibiting bacterial α-amylase and no activity towards fungal α-amylase. Moreover, both isomers show no inhibitory activity towards mammalian α-glucosidase. Kinetic analysis revealed that using starch as the substrate, dracoflavan B was a non-competitive α-amylase inhibitor with a Ki value of 11.7μM. Lack of α-amylase inhibition for proanthocyanidin A2 dimer demonstrated that dracoflavan B hydrophobic nature of the B, A', C' and B' rings are important for its α-amylase inhibition. In addition, selective chemical modification studies revealed that the phenolic group is also vital to dracoflavan B for its pancreatic α-amylase inhibition activity. Without the A ring phenolic hydrogen bond donor, the derivatives of dracoflavan B showed detrimental α-amylase inhibition. On the contrary, galloylation on the A ring phenolic OH group enhanced the activity as shown by the low IC50 (12μM) against α-amylase which is 56% more potent as compared to dracoflavan B., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In this study a novel series of poly-hydroxyl functionalized acridine derivatives (L1-L9) was synthesized and their inhibitory activities against α-Glucosidase (α-Gls) and α-Amylase (α-Amy) were evaluated, spectroscopically. The synthetic compounds consist of three different substructures, including a 4-(4-aminophenoxy) phenyl group (R3), an acridine moiety (R2) and a poly-hydroxy chain (R1). The results indicate that among the synthetic compounds, L5 with a chromeno[3',4':5,6]pyrido[2,3-d]pyrimidine moiety demonstrates the highest inhibitory activity against both yeast and rat α-Gls enzymes. Also, L2 with the thioxo-pyrido[2,3-d:6,5-d'] dipyrimidine moiety plays an important role in the inhibition of yeast α-Gls. In addition, the results may suggest a significant role for the nature of sugar moiety of the synthetic compounds in their inhibitory action against α-Gls. Moreover, in comparison with Acarbose, which is a widely used anti-diabetic drug, these compounds show negligible inhibitory activity against pancreatic α-Amy, which is important in the term of their reduced susceptibility for possible development of the intestinal disturbance side effects. Results of this study may suggest these synthetic compounds as novel molecular templates for construction of potentially anti-diabetic drugs with the ability for more convenient management of postprandial hyperglycemia., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Although considerable information is available about amylolysis rate, extent and pattern of granular starches, the underlying mechanisms of enzyme action and interactions are not fully understood, partly due to the lack of direct visualisation of enzyme binding and subsequent hydrolysis of starch granules. In the present study, α-amylase (AA) from porcine pancreas was labelled with either fluorescein isothiocyanate (FITC) or tetramethylrhodamine isothiocyanate (TRITC) fluorescent dye with maintenance of significant enzyme activity. The binding of FITC/TRITC-AA conjugate to the surface and interior of granules was studied under both non-hydrolysing (0 °C) and hydrolysing (37 °C) conditions with confocal microscopy. It was observed that enzyme binding to maize starch granules under both conditions was more homogenous compared with potato starch. Enzyme molecules appear to preferentially bind to the granules or part of granules that are more susceptible to enzymic degradation. The specificity is such that fresh enzyme added after a certain time of incubation binds at the same location as previously bound enzyme. By visualising the enzyme location during binding and hydrolysis, detailed information is provided regarding the heterogeneity of granular starch digestion., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

In order to investigate the inhibitory effects and possible mechanisms of Oolong tea polyphenols, (-)-epigallocatechin gallate (EGCG) and (-)-epigallocatechin 3-O-(3-O-methyl) gallate (EGCG3″Me) on pancreatic α-amylase, the inhibition, enzyme kinetics, ultraviolet (UV) absorption spectrum and fluorescence spectrum of α-amylase were investigated. The results showed that Oolong tea polyphenols, EGCG, and EGCG3″Me all exhibited inhibitory effects against α-amylase, and their half inhibitory concentration (IC50) values were 0.375, 0.350, and 0.572 mg/mL, respectively. The results of Lineweaver-Burk double reciprocal plot indicated that the inhibitory types of Oolong tea polyphenols and EGCG were competitive, whereas EGCG3″Me was in a noncompetitive pattern. Oolong tea polyphenols, EGCG, and EGCG3″Me all induced red-shift of UV absorbance and quenching of fluorescence of α-amylase, suggesting possible changes in the conformation of α-amylase. The differences of inhibitory effects and inhibition types for EGCG and EGCG3″Me might be due to their structural difference (the hydroxyl group at C-3 in D ring of EGCG substituted by methoxy group, forming EGCG3″Me).

Background: Inhibition of digestive enzymes is one of the most widely studied mechanisms used to determine the potential efficacy of natural products as anti-obesity agents. In vitro studies reported here were performed to evaluate the inhibitory activity of formulations of edible plants from Italy on amylase and lipase by monitoring the hydrolysis of nitrophenyl caprilate and the hydrolysis of glycoside bonds in digestible carbohydrate foods., Results: The formulation obtained from Capparis sicula exhibited the strongest inhibitory effect on pancreatic lipase (IC50 = 0.53 mg mL(-1) ) while the Borago officinalis formulation exhibited the strongest inhibitory effect on α-amylase (IC50 = 31.61 µg mL(-1) ). In order to characterise the extracts, high-performance thin-layer chromatography analysis of the formulations was performed, revealing the predominance of (±)-catechin in Mentha aquatica formulation, rutin in C. sicula, and caffeic acid and chlorogenic acid in Echium vulgare., Conclusion: The results obtained indicated that the extracts of C. sicula and B. officinalis could be good candidates for further studies to isolate pancreatic lipase and α-amylase inhibitors, respectively., (© 2013 Society of Chemical Industry.)

Pancreatic triacylglycerol lipase (PL), alpha-amylase and alpha-glucosidase are interesting pharmacological targets for the management of dyslipidemia, atherosclerosis, and obesity-diabetes. Limonium spp (Plumbaginaceae) are endemic to Sardinia, Italy. Comparable with acarbose, aqueous extracts (AE) of L. contortirameum and L. virgatum, and their phytoconstituent gallic acid concentration gradients (mg/mL) were identified as in vitro potent (p<0.001, n=3) and efficacious dual inhibitors of alpha-amylase and alpha-glucosidase with respective IC50 (mg/mL) values of 0.6 +/- 0.1, 1.2 +/- 0.1 and 0.15 +/- 0.02. Equivalent to orlistat (PL IC50 of 0.114 +/- 0.004 microg/mL), L. contortirameum, L. virgatum AE and their phytoprinciple gallic acid inhibited PL substantially (p<0.001, n=3) in a dose-dependent manner in vitro with PL- IC50 (microg/mL) of 920.4 +/- 105.2, 593.1 +/- 56.8 and 8.4 +/- 0.9, respectively. LC-MS analysis of extracts revealed the presence of several phenolic compounds in their aglycon and glycoside forms. These are catechins, flavones, epigallocatechins and flavonols. Flavonoid- and polyphenol-rich L contortirameum and L. virgatum, modulating gastrointestinal carbohydrate and lipid digestion and absorption, may be advocated as candidates for obesity-diabetes prevention and phytotherapy.

α-Amylases hydrolyze α- 1,4-glycosidic bonds during assimilation of biological macromolecules. The amino acid sequences of these enzymes in thousands of diverse organisms are known and the 3D structures of several proteins have been solved. The 3D structure analysis of these universal enzymes from diverse organisms has been studied by the generation of phylogenetic trees and structure based sequence analysis to generate a metric for the degree of conservation that is responsible for individual speciation. Greater similarities are observed between reference NCBI tree and structure based phylogenetic tree compared to sequence based phylogenetic tree indicating that structures truly represent the functional aspects of proteins than from the sequence information alone. We report differences in the profile specific conserved and insertion/deletion regions, factors responsible for the Ca(2+) and Cl(-) ion binding and the disulfide connectivity pattern that discriminate the enzymes over evolution.

Series of new benzyl 2H-chromenones 6a-n was synthesized by Pechmann condensation of substituted benzyl resorcinols 2a-c and 3a with various β-ketoesters such as ethyl 3-oxobutanoate, ethyl 3-oxo-3-phenylpropanoate, ethyl 4- chloro-3-oxobutanoate, ethyl 4,4,4-trifluoro-3-oxobutanoate and ethyl 2-chloro-3-oxobutanoate 5a-e in very good yields. Synthesized compounds 6a-n were screened for their α-amylase inhibitory, and ABTS.+ scavenging activities. In the present series of compounds, compound 8-benzyl-7-hydroxy-4-phenyl-2H-chromen-2-one 6c and 8-benzyl-7-hydroxy-4- methyl-2H-chromen-2-one 6a were most potent ABTS.+ radical scavenging and α-amylase inhibitor. Although compound 6,8-dibenzyl-7-hydroxy-4-(trifluoromethyl)-2H-chromen-2-one 6h displayed potent ABTS.+ free radical scavenging potential, it was found poor in inhibiting pancreatic α-amylase.

A novel method for the synthesis of substituted pyrroles catalyzed by α-amylase from hog pancreas via Paal-Knorr reaction was developed. A series of pyrrole derivatives were synthesized under mild conditions and the products were obtained with good to excellent yields (60-99 %). The impact of factors, such as solvents, enzyme amount, and temperature, on the reaction were investigated. This study reports an efficient route for the synthesis of N-substituted pyrrole derivatives.

Starch digestion in the human body is typically viewed in a sequential manner beginning with α-amylase and followed by α-glucosidase to produce glucose. This report indicates that the two enzyme types can act synergistically to digest granular starch structure. The aim of this study was to investigate how the mucosal α-glucosidases act with α-amylase to digest granular starch. Two types of enzyme extracts, pancreatic and intestinal extracts, were applied. The pancreatic extract containing predominantly α-amylase, and intestinal extract containing a combination of α-amylase and mucosal α-glucosidase activities, were applied to three granular maize starches with different amylose contents in an in vitro system. Relative glucogenesis, released maltooligosaccharide amounts, and structural changes of degraded residues were examined. Pancreatic extract-treated starches showed a hydrolysis limit over the 12 h incubation period with residues having a higher gelatinization temperature than the native starch. α-Amylase combined with the mucosal α-glucosidases in the intestinal extract showed higher glucogenesis as expected, but also higher maltooligosaccharide amounts indicating an overall greater degree of granular starch breakdown. Starch residues after intestinal extract digestion showed more starch fragmentation, higher gelatinization temperature, higher crystallinity (without any change in polymorph), and an increase of intermediate-sized or small-sized fractions of starch molecules, but did not show preferential hydrolysis of either amylose or amylopectin. Direct digestion of granular starch by mammalian recombinant mucosal α-glucosidases was observed which shows that these enzymes may work either independently or together with α-amylase to digest starch. Thus, mucosal α-glucosidases can have a synergistic effect with α-amylase on granular starch digestion, consistent with a role in overall starch digestion beyond their primary glucogenesis function.

Extracts of eleven traditional Chinese medicines (TCM) with a reputation of usefulness in treating diabetes mellitus were examined for alpha-glucosidase and alpha-amylase inhibitory activities in vitro. The extract with the highest activity was selected for further characterization. The extract of the root bark of Aralia taibaiensis (EAT) outperformed other extracts in the assays with IC50 values of 0.48 +/- 0.01 mg/mL (BSG), 0.41 +/- 0.02mg/mL (SCG), 0.61 +/- .03mg/mL (BLA) and 0.77 +/- 0.03mg/mL (PPA), respectively. To identify which constituents were responsible for the activities, thirteen triterpenoid saponins were isolated from EAT and examined for their inhibitory effects against alpha-glucosidase and alpha-amylase. The results revealed that saponins 2, 3, 4 (IC50: 0.83 +/- 0.05 microM for BSG and IC50: 0.72 +/- 0.03 microM for SCG), 5, 6, 7, 9, 10, 11 and 12 (IC50: 1.07 +/- 0.04 micro.M for BSG and IC50: 0.93 +/- 0.05 micro.M for SCG) showed alpha-glucosidase inhibitory activities, while 2, 3, 4 (IC50: 0.93 +/- 0.04 micro.M for PPA), 5, 6, 7, 9, 10, 11 and 12 (IC50: 1.02 +/- 0.03 micro.M for PPA) possessed significant alpha-amylase inhibitory activities. In addition, the structure-activity relationship of the thirteen saponins was discussed based on their structure features and diabetes mellitus related activities. It is suggested that the glucuronic acid unit at C-3 of the aglycone is the imperative functional group of the antidiabetic activities, and two characteristic structural features are responsible for the remarkable alpha-glucosidase and alpha-amylase inhibitory activities.

In vitro studies of α-amylase degradation of α-, β- and γ-cyclodextrins and 2-hydroxypropyl-β- and -γ-cyclodextrins were investigated spectrophotometrically by measuring the formation of reducing sugars, the reaction products of α-amylase degradation. This was done to evaluate potential degradation and thereby biological conversion of the cyclodextrins if dosed orally, as the intestinal tract contains α-amylase for digestive purposes. The results demonstrated that only γ- and 2-hydroxypropyl-γ-cyclodextrins can be degraded by α-amylase to a relevant extent, that is, γ- and 2-hydroxypropyl-γ-cyclodextrins have different biopharmaceutical behaviours than the other evaluated cyclodextrins. The rate of degradation was affected by the addition of the inclusion complex forming additives flurbiprofen, ibuprofen and benzo[a]pyrene. This effect between the degradation dynamics and the included additives was caused by a correlation between solubility of the additives and the stability of the complex., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: Plant-based foods have been used in traditional health systems to treat diabetes mellitus. The successful prevention of the onset of diabetes consists in controlling postprandial hyperglycemia by the inhibition of α-glucosidase and pancreatic α-amylase activities, resulting in aggressive delay of carbohydrate digestion to absorbable monosaccharide. In this study, five plant-based foods were investigated for intestinal α-glucosidase and pancreatic α-amylase. The combined inhibitory effects of plant-based foods were also evaluated. Preliminary phytochemical analysis of plant-based foods was performed in order to determine the total phenolic and flavonoid content., Methods: The dried plants of Hibiscus sabdariffa (Roselle), Chrysanthemum indicum (chrysanthemum), Morus alba (mulberry), Aegle marmelos (bael), and Clitoria ternatea (butterfly pea) were extracted with distilled water and dried using spray drying process. The dried extracts were determined for the total phenolic and flavonoid content by using Folin-Ciocateu's reagent and AlCl3 assay, respectively. The dried extract of plant-based food was further quantified with respect to intestinal α-glucosidase (maltase and sucrase) inhibition and pancreatic α-amylase inhibition by glucose oxidase method and dinitrosalicylic (DNS) reagent, respectively., Results: The phytochemical analysis revealed that the total phenolic content of the dried extracts were in the range of 230.3-460.0 mg gallic acid equivalent/g dried extract. The dried extracts contained flavonoid in the range of 50.3-114.8 mg quercetin equivalent/g dried extract. It was noted that the IC50 values of chrysanthemum, mulberry and butterfly pea extracts were 4.24±0.12 mg/ml, 0.59±0.06 mg/ml, and 3.15±0.19 mg/ml, respectively. In addition, the IC50 values of chrysanthemum, mulberry and butterfly pea extracts against intestinal sucrase were 3.85±0.41 mg/ml, 0.94±0.11 mg/ml, and 4.41±0.15 mg/ml, respectively. Furthermore, the IC50 values of roselle and butterfly pea extracts against pancreatic α-amylase occurred at concentration of 3.52±0.15 mg/ml and 4.05±0.32 mg/ml, respectively. Combining roselle, chrysanthemum, and butterfly pea extracts with mulberry extract showed additive interaction on intestinal maltase inhibition. The results also demonstrated that the combination of chrysanthemum, mulberry, or bael extracts together with roselle extract produced synergistic inhibition, whereas roselle extract showed additive inhibition when combined with butterfly pea extract against pancreatic α-amylase., Conclusions: The present study presents data from five plant-based foods evaluating the intestinal α-glucosidase and pancreatic α-amylase inhibitory activities and their additive and synergistic interactions. These results could be useful for developing functional foods by combination of plant-based foods for treatment and prevention of diabetes mellitus.

Context: Spices have been used as food adjuncts and in folklore for ages. Inhibition of key enzymes (α-amylase and α-glucosidase) involved in the digestion of starch and protection against free radicals and lipid peroxidation in pancreas could be part of the therapeutic approach towards the management of hyperglycemia and dietary phenolics have shown promising potentials., Objective: This study investigated and compared the inhibitory properties of aqueous extracts of some tropical spices: Xylopia aethiopica [Dun.] A. Rich (Annonaceae), Monodora myristica (Gaertn.) Dunal (Annonaceae), Syzygium aromaticum [L.] Merr. et Perry (Myrtaceae), Piper guineense Schumach. et Thonn (Piperaceae), Aframomum danielli K. Schum (Zingiberaceae) and Aframomum melegueta (Rosc.) K. Schum (Zingiberaceae) against α-amylase, α-glucosidase, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and sodium nitroprusside (SNP)-induced lipid peroxidation in rat pancreas--in vitro using different spectrophotometric method., Materials and Methods: Aqueous extract of the spices was prepared and the ability of the spice extracts to inhibit α-amylase, α-glucosidase, DPPH radicals and SNP-induced lipid peroxidation in rat pancreas--in vitro was investigated using various spectrophotometric methods., Result: All the spice extracts inhibited α-amylase (IC(50) = 2.81-4.83 mg/mL), α-glucosidase (IC(50) = 2.02-3.52 mg/mL), DPPH radicals (EC(50) = 15.47-17.38 mg/mL) and SNP-induced lipid peroxidation (14.17-94.38%), with the highest α-amylase & α-glucosidase inhibitory actions and DPPH radical scavenging ability exhibited by X. aethiopica, A. danielli and S. aromaticum, respectively. Also, the spices possess high total phenol (0.88-1.3 mg/mL) and flavonoid (0.24-0.52 mg/mL) contents with A. melegueta having the highest total phenolic and flavonoid contents., Discussion and Conclusion: The inhibitory effects of the spice extracts on α-amylase, α-glucosidase, DPPH radicals and SNP-induced lipid peroxidation in pancreas (in vitro) could be attributed to the presence of biologically active phytochemicals such as phenolics and some non-phenolic constituents of the spices. Furthermore, these spices may exert their anti-diabetic properties through the mechanism of enzyme inhibition, free radicals scavenging ability and prevention of lipid peroxidation.

Starch nanocrystals (SNCs) are crystalline platelets resulting from the acid hydrolysis of starch. A limiting factor for their more widespread use is their preparation duration. Therefore, this study investigates the possibility of developing an enzymatic pretreatment of starch to reduce the acid hydrolysis duration. A screening of three types of enzymes, namely, α-amylase, β-amylase, and glucoamylase, is proposed, and the latter was selected for a pretreatment. Compared with the regular kinetics of hydrolysis for preparing SNC, that of pretreated starch was much faster. The extent of hydrolysis normally reached in 24 h was obtained after only 6 h, and the regular final yield (15% after 5 days) was reached in 45 h. AFM and X-ray diffraction measurements confirmed that the obtained nanoparticles were indeed SNC.

In this study, the interactions of free and bound phenolic-rich extracts from shaddock peels (popular in folklore for the management of diabetes and hypertension) with α-amylase and α-glucosidase (key enzymes linked to type-2 diabetes) and angiotensin I-converting enzyme (ACE) (key enzyme linked to hypertension) were assessed. The free phenolics of shaddock (Citrus maxima) peels were extracted with 80% acetone, while the bound phenolics were extracted from the alkaline and acid hydrolyzed residue with ethyl acetate; and their interaction with the enzymes were assessed. The phenolic extracts inhibited α-amylase, α-glucosidase and ACE enzyme activities in a dose-dependent manner; however, bound phenolics had significantly higher (P<0.05) α-amylase inhibitory activities, than free phenolics, which had significantly higher (P<0.05) ACE inhibitory activities. There was no significant difference (P>0.05) in their α-glucosidase inhibitory activities. The stronger inhibition of α-glucosidase when compared to α-amylase is of great pharmaceutical importance. The phenolic inhibited sodium nitroprusside induced lipid peroxidation in pancreas in a dose dependent manner. Therefore, free and bound phenolic extracts from shaddock peels could be used as nutraceutical for the management of hypertension and type-2 diabetes., (Copyright © 2012 Diabetes India. Published by Elsevier Ltd. All rights reserved.)

This study determined the in vitro inhibitory effects of cocoa extracts and procyanidins against pancreatic α-amylase (PA), pancreatic lipase (PL), and secreted phospholipase A(2) (PLA(2)) and characterized the kinetics of such inhibition. Lavado, regular, and Dutch-processed cocoa extracts as well as cocoa procyanidins (degree of polymerization (DP) = 2-10) were examined. Cocoa extracts and procyanidins dose-dependently inhibited PA, PL, and PLA(2). Lavado cocoa extract was the most potent inhibitor (IC(50) = 8.5-47 μg/mL). An inverse correlation between log IC(50) and DP (R(2) > 0.93) was observed. Kinetic analysis suggested that regular cocoa extract, the pentamer, and decamer inhibited PL activity in a mixed mode. The pentamer and decamer noncompetitively inhibited PLA(2) activity, whereas regular cocoa extract inhibited PLA(2) competitively. This study demonstrates that cocoa polyphenols can inhibit digestive enzymes in vitro and may, in conjunction with a low-calorie diet, play a role in body weight management.

The inhibitory activity on pancreatic α-amylase by cyanidin-3-rutinoside was examined in vitro. The IC₅₀ value of cyanidin-3-rutinoside against pancreatic α-amylase was 24.4 ± 0.1 μM. The kinetic analysis revealed that pancreatic α-amylase was inhibited by cyanidin-3-rutinoside in a non-competitive manner. The additive inhibition of a combination of cyanidin-3-rutinoside with acarbose against pancreatic α-amylase was also found. These results provide the first evidence for the effect of cyanidin-3-rutinoside in a retarded absorption of carbohydrates by inhibition of pancreatic α-amylase which may be useful as a potential inhibitor for prevention and treatment of diabetes mellitus.

Trans-chalcone (1,3-diphenyl-2-propen-1-one), a biphenolic core structure of flavonoids precursor was tested for inhibitory activity toward alpha-amylase. Porcine pancreatic alpha-amylase was observed to be effectively inhibited by this compound, which showed competitive behavior with a K(i) of 48 μM. Soluble starch (the natural substrate of the enzyme) was used in this study in order to obtain more realistic results. The possible binding mode of the compound was assessed in silico, and the two residues Trp59, and Tyr62 were proposed as main interacting residues with trans-chalcone. In conclusion, this compound could be used to design effective inhibitors of alpha-amylase.

The bark extract of Acacia mearnsii showed strong lipase and α-amylase inhibition activities. Fractionation of the extract by column chromatography and subsequent (13)C NMR and MALDI-TOF-MS analysis revealed that the active substances are proanthocyanidin oligomers mainly composed of 5-deoxyflavan-3-ol units. In addition, 4'-O-methylrobinetinidol 3'-O-β-D-glucopyranoside, fisetinidol-(4α,6)-gallocatechin, and epirobinetinidol-(4β,8)-catechin were isolated as new compounds, and their structures were determined from spectroscopic data. Furthermore, a modified thiol degradation method using strongly acidic conditions was applied to the extract to yield three thiol degradation products derived from robinetinidol units. This method is useful for characterizing acacia proanthocyanidins (wattle tannins).

The present study was to investigate in vitro alpha-glucosidase, pancreatic alpha-amylase and protein glycation inhibitory activities of nine edible plants. The results indicated that total phenolics, flavonoids, and condensed tannins of nine edible plants showed marked variations, ranging from 12.2 to 80.1 mg gallic acid equivalent/g extract, 2.34 to 13.65 mg quercetin equivalent/g extract, and 97.2 to 460.1 mg catechin equivalent/g extract, respectively. Our findings showed that grape seed, Cat's whiskers and Sweetleaf extract were the most effective pancreatic alpha-amylase, intestinal maltase, and sucrase inhibitor with IC(50) values of 0.29 +/- 0.01 mg/ml, 0.97 +/- 0.10 mg/ml and 0.86 +/- 0.01 mg/ml, respectively. All extracts (1 mg/ml) markedly inhibited the glycation of bovine serum albumin in fructose-mediated non-enzyme glycation by 50-30% at week 1. It was found that Pennywort maintained the high percentage inhibition among those of the extracts during the 4 weeks of experiment. These edible plants may be used for controlling blood glucose level and prevention of the development of type 2 diabetes.

YCP is a marine polysaccharide with anti-tumor and immune-modulating effects. This study evaluated the effect of enzymatic degradation of YCP by alpha-amylases from different origins on its immunological activity and binding ability to the macrophages. YCP was hydrolyzed by alpha-amylases isolated from Aspergillus oryzae, Bacillus licheniformis, Barley malt, and Porcine pancreas respectively, then four fragments with unique molecular weight (termed: YCP-Ao, YCP-Bl, YCP-Bm, and YCP-Pp, respectively) were obtained. The four fragments showed different immunological activity and the ability to bind to macrophages. Among them, YCP-Ao possessed almost equivalent immunological activity compared to the original YCP, while such properties were not retained in YCP-Bl. Our further study showed that YCP-Ao prevented YCP from binding to macrophages. In conclusion, YCP-Ao and YCP might have similar active regions., (Crown Copyright (c) 2009. Published by Elsevier Masson SAS. All rights reserved.)

While covalent catalytic intermediates of retaining alpha-transglycosylases have been structurally characterized previously, no such information for a hydrolytic alpha-amylase has been obtained. This study presents a new "in situ" enzymatic elongation methodology that, for the first time, has allowed the isolation and structural characterization of a catalytically competent covalent glycosyl-enzyme intermediate with human pancreatic alpha-amylase. This has been achieved by the use of a 5-fluoro-beta-l-idosyl fluoride "warhead" in conjunction with either alpha-maltotriosyl fluoride or 4'-O-methyl-alpha-maltosyl fluoride as elongation agents. This generates an oligosaccharyl-5-fluoroglycosyl fluoride that then reacts with the free enzyme. The resultant covalent intermediates are extremely stable, with hydrolytic half-lives on the order of 240 h for the trisaccharide complex. In the presence of maltose, however, they undergo turnover via transglycosylation according to a half-life of less than 1 h. Structural studies of intermediate complexes unambiguously show the covalent attachment of a 5-fluoro-alpha-l-idosyl moiety in the chair conformation to the side chain of the catalytic nucleophile D197. The elongated portions of the intermediate complexes are found to bind in the high-affinity -2 and -3 binding subsites, forming extensive hydrogen-bonding interactions. Comparative structural analyses with the related noncovalent complex formed by acarbose highlight the structural rigidity of the enzyme surface during catalysis and the key role that substrate conformational flexibility must play in this process. Taken together, the structural data provide atomic details of several key catalytic steps. The scope of this elongation approach to probe the active sites and catalytic mechanisms of alpha-amylases is further demonstrated through preliminary experiments with porcine pancreatic alpha-amylase.

Chlorogenic acid (5-caffeoylquinic acid, 5-CQA) is a kind of polyphenol and is richly included in green coffee beans. The inhibitory effects of 5-CQA and its components, caffeic acid (CA) and quinic acid (QA), on the two porcine pancreas alpha-amylase (PPA) isozymes, PPA-I and PPA-II, were investigated using p-nitrophenyl-alpha-D-maltoside as substrate at pH 6.9 and 30 degrees C. The inhibition potencies of the respective inhibitors against both PPA isozymes were almost the same and in the order of 5-CQA > CA >> QA. Their IC(50) values were 0.07-0.08 mM, 0.37-0.40 mM, and 25.3-26.5 mM, respectively. The inhibition mechanisms of 5-CQA and CA were investigated by kinetic analyses, and the inhibitor constants K(i) and K(i)' (for the free enzyme and enzyme-substrate complex, respectively) were determined. It was indicated that 5-CQA and CA showed mixed-type inhibition with K(i) > K(i)' against both PPA-I and PPA-II. The binding of PPA-I or PPA-II with 5-CQA or CA was all exothermic and enthalpy-driven. QA is a poor inhibitor, and its inhibitory mode was unique and hardly analyzed by a simple Michaelis-Menten-type interaction between the enzyme and inhibitor. However, it was shown that the inhibitory activity of CA was enhanced 5 times by ester-bond formation with QA in the form of 5-CQA. These results provide us with significant hints for the development of alpha-amylase inhibitors useful for the prevention of diabetes and obesity.

Porcine pancreatic alpha-amylase (PPA) and its isoforms (PPA-I and PPA-II) were deglycosylated by peptide-N-glycosidase F (PNGase F) to investigate the role of bound carbohydrate. On deglycosylation, the effect on thermal stability was less pronounced. Deglycosylation resulted in a shift of the mid-point of thermal transition by 1-2 degrees C towards lower temperature. The fluorescence emission maxima of PPA, PPA-I and PPA-II were found to be 340nm indicating the presence of tryptophan residues in a fairly hydrophilic environment. A red shift in emission spectra accompanied by an increase in fluorescence intensity was observed upon deglycosylation.

A high-performance determination system for alpha-amylase isoenzyme activities in human plasma involving microchip electrophoresis with a plastic chip was developed. The combination of microchip electrophoresis for substrate and hydrolysate separation and an immunoinhibition method for the differentiation of isoenzyme activities using antihuman salivary amylase (S-AMY) mAb allowed the highly selective determination of amylase isoenzyme (S-AMY and pancreatic amylase (P-AMY)) activities even in a complex matrix such as a crude plasma sample. We used 8-aminopyrene-1,3,6-trisulfonic acid (APTS)-labeled maltohexaose (G6) as a substrate. Amylase in a human plasma sample hydrolyzed APTS-G6 into APTS-maltotriose (G3) and G3, which was measured as the fluorescence intensity of APTS-G3 on microchip electrophoresis. A double logarithm plot revealed a linear relationship between amylase activity and fluorescence intensity in the range of 5-500 U/L of amylase activity (r2=0.9995, p<0.01), and the LOD was 4.38 U/L. Amylase activities in 13 subjects determined by the present method were compared with the results obtained by conventional methods with nitrophenylated oligosaccharides as substrates, respectively. Good correlations were observed for each method on simple linear regression analysis (both p<0.01). The reproducibilities of within-days for total amylase and P-AMY were 2.98-6.27 and 3.83-6.39%, respectively, and these between-days were 2.88-5.66 and 3.64-5.63%, respectively. This system enables us to determine amylase isoenzyme activities in human plasma with high sensitivity and accuracy, and thus will be applicable to clinical diagnosis.

Four aminooligosaccharides were isolated and purified from the culture filtrate of Streptomyces coelicoflavus ZG0656. Their chemical structures were determined by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and two-dimensional nuclear magnetic resonance (NMR) spectroscopy. The names acarviostatins I03, II03, III03, and IV03 were given to the oligomers due to their acarviosin core structures. Acarviostatins III03 and IV03, which contain three and four acarviosin-glucose moieties, respectively, were identified as novel compounds. The four acarviostatins were all mixed noncompetitive inhibitors of porcine pancreatic alpha-amylase (PPA). The inhibition constants (K(i)) for acarviostatins III03 and IV03 were 0.008 and 0.033muM, respectively. Acarviostatin III03 is the most effective alpha-amylase inhibitor known to date, with a K(i) value 260 times more potent than acarbose.