Mammalian Α-glucosidase Research Articles

Therapeutic Potential of Rare Sesterterpenoids from Aspergillus Variecolor Strain SDG and Docking Studies.

Ethyl acetate extract of the cultures of the soil-derived filamentous fungus, Aspergillus variecolor SDG strain from Nallamala forest resulted in the isolation of extremely rare sesterterpenoids, stellatic acid (1) and andilesin C (2). We report a thorough chemical characterization of these compounds using various spectroscopic techniques and evaluation of their in vitro preclinical therapeutic potential. Stellatic acid exhibits potent antioxidant activity with an IC50 of 38 μg/mL and significant anticancer activity against HeLa, HepG2, MCF7, and A549 cancer cell lines with an IC50 of 7-12 μM. On the other hand, andilesin C displayed moderate cytotoxicity against DU145 and B16F10 cancer cell lines but lacked antioxidant activity. Furthermore, the potential hypoglycemic property of stellatic acid was evaluated by measuring its inhibitory effect against α-glucosidase. It exhibited tenfold potency against yeast α-glucosidase (IC50 101.73 μg/mL) than mammalian α-glucosidase (IC50 1000.00 μg/mL). Docking studies were also performed to suggest the interaction mode of stellatic acid in the α-glucosidase enzyme active site. Notably, yeast α-glucosidase shows a higher affinity towards stellatic acid than mammalian α-glucosidase (3TOP). Thus, the in vitro preclinical study of stellatic acid suggests its potential efficacy in therapeutic drug development.

Inhibition of starch hydrolysis during in vitro co-digestion of pasta with phenolic compound-rich vegetable foods

The ability of phenolic compounds to inhibit amylolytic enzymes activities has been investigated, suggesting their possible role in type-2 diabetes management. However, these studies have been carried out with purified enzymes and synthetic substrates and are distant from simulating a real physiological situation. The objective of the present research was to evaluate the ability of phenolic-rich vegetable foods to inhibit starch hydrolysis during in vitro co-digestion with pasta resulting in a potential anti-diabetic effect and mimicking as closely as possible a real scenario. Some tested vegetable foods, such as capers, red-skinned onion, red radish, and olives, determined a decrease in starch hydrolysis by 21.5%–31.7% during in vitro co-digestion with pasta. The quali-quantitative phenolic profiles of in vitro co-digested samples were elucidated and selected standard compounds were tested for their ability to inhibit porcine pancreatic α-amylase and mammalian α-glucosidase. The inhibitory potential of these compounds, especially against α-glucosidase, explained the effect observed during co-digestion experiments. The most active phenolic compounds against α-glucosidase were quercetin-4’-O-glucoside, quercetin-3-O-rutinoside, luteolin-7-O-glucoside and quercetin-3-O-glucoside-4’-O-glucoside with IC50 values of 20.67, 52.23, 68.84 and 87.58 μmol/L, respectively. This is the first report suggesting that these compounds are potent inhibitors of mammalian α-glucosidase. This study indicates that consuming starchy foods (i.e., pasta) with phenolic-rich vegetable foods may result in an inhibition of starch digestion possibly reducing the post-prandial glucose levels.

Phytochemical profiling, human insulin stability and alpha glucosidase inhibition of Gymnema latifolium leaves aqueous extract: Exploring through experimental and in silico approach

Diabetes mellitus Type 2 (DM2T) is a rapidly expanding metabolic endocrine disorder worldwide. It is caused due to inadequate insulin secretion by pancreatic beta cells as well as development of insulin resistance. This study aimed to investigate the anti-α-glucosidase, insulin stabilization effect, and non-cytotoxic nature of Gymnema latifolium leaf aqueous extract (GLAE). FTIR analysis revealed the functional groups of compounds present in GLAE. Through LC/ESI-MS/MS analysis, about 12 compounds which belongs to different classes, triterpene glycosides, flavonoids, phenolics, stilbene glycosides and chlorophenolic glycosides were identified. GLAE showed in vitro antioxidant activity. GLAE stabilized insulin by increasing its α-helical content. GLAE inhibited the mammalian α-glucosidase (IC50 = 144 μg/mL) activity through competitive mode (Ki = 61.30 µg/mL). GLAE did not affect the viability of normal cell line (Vero cell line) which shows its non-toxic nature. Molecular docking of phytocompounds identified in GLAE was done with human α-glucosidase and insulin. The top 2 compounds [Gymnema saponin V (GSV) and quercetin 3-(2-galloylglucoside) (QGG) with α-glucosidase; GSV and Z)-resveratrol 3,4′-diglucoside (RDG) with human insulin] with low binding free energy were subjected to 100 ns molecular dynamics simulation to ascertain the stable binding of ligand with protein. The MM/GBSA analysis revealed binding free energy of GSV/α-glucosidase and QGG /α-glucosidase to be - 20.9935 and, − 30.9461 kcal/mol, respectively. Altogether GLAE is valuable source of anti-α-glucosidase inhibitors and insulin stabilizing compounds, suggesting potential lead for further exploration as complementary medicine against DM2T.

Slow digestion properties of long-sized isomaltooligosaccharides synthesized by a transglucosidase from Thermoanaerobacter thermocopriae.

Isomaltooligosaccharides (IMOs) are widely used as prebiotic ingredients that promote colon health; however, recent studies revealed that these are slowly hydrolyzed to glucose within the small intestine. Here, novel α-glucans with a higher number of α-1,6 linkages were synthesized from maltodextrins using the Thermoanaerobacter thermocopriae-derived transglucosidase (TtTG) to decrease susceptibility to hydrolysis and improve slow digestion properties. The synthesized long-sized IMOs (l-IMOs; 70.1% of α-1,6 linkages), comprising 10-12 glucosyl units, exhibited slow hydrolysis to glucose when compared to commercial IMOs under treatment with mammalian α-glucosidase level. In male mice, the ingestion of l-IMOs significantly decreased the post-prandial glycemic response compared to other samples (p<0.05). Therefore, enzymatically synthesized l-IMOs can be applied as functional ingredients for the modulation of blood glucose homeostasis in obesity, Type 2 diabetes, and other chronic diseases.

Screening and Elucidation of Chemical Structures of Novel Mammalian α-Glucosidase Inhibitors Targeting Anti-Diabetes Drug from Herbals Used by E De Ethnic Tribe in Vietnam.

Among ten extracts of indigenous medicinal plants, the MeOH extract of Terminalia triptera Stapf. (TTS) showed the most efficient mammalian α-glucosidase inhibition for the first time. The data of screening bioactive parts used indicated that the TTS trunk bark and leaves extracts demonstrated comparable and higher effects compared to acarbose, a commercial anti-diabetic drug, with half-maximal inhibitory concentration (IC50) values of 181, 331, and 309 µg/mL, respectively. Further bioassay-guided purification led to the isolation of three active compounds from the TTS trunk bark extract and identified as (-)-epicatechin (1), eschweilenol C (2), and gallic acid (3). Of these, compounds 1 and 2 were determined as novel and potent mammalian α-glucosidase inhibitors. The virtual study indicated that these compounds bind to α-glucosidase (Q6P7A9) with acceptable RMSD values (1.16-1.56 Å) and good binding energy (DS values in the range of -11.4 to -12.8 kcal/mol) by interacting with various prominent amino acids to generate five and six linkages, respectively. The data of Lipinski's rule of five and absorption, distribution, metabolism, excretion and toxicity (ADMET)-based pharmacokinetics and pharmacology revealed that these purified compounds possess anti-diabetic drug properties, and the compounds are almost not toxic for human use. Thus, the findings of this work suggested that (-)-epicatechin and eschweilenol C are novel potential mammalian α-glucosidase inhibitor candidates for type 2 diabetes treatment.

Macromolecular α-glucans with α-1,3/α-1,4 branching structures produced using dual glycosyltransferases: Elucidation of physicochemical and slowly digestible properties

Amylosucrase from Neisseria polysaccharea (NpAS) produces the linear amylose-like α-glucans by the elongation property from sucrose, and 4,3-α-glucanotransferase from Lactobacillus fermentum NCC 2970 (4,3-αGT) newly synthesizes the α-1,3 linkages after cleaving the α-1,4 linkages by the glycosyltransferring property. This study focused on the synthesis of high molecular α-1,3/α-1,4-linked glucans by combining NpAS and 4,3-αGT and analyzed their structural and digestive properties. The enzymatically synthesized α-glucans have a molecular weight of >1.6 × 107 g mol−1, and the α-4,3 branching ratios on the structures increased as the amount of 4,3-αGT increased. The synthesized α-glucans were hydrolyzed to linear maltooligosaccharides and α-4,3 branched α-limit dextrins (α-LDx) by human pancreatic α-amylase, and the amounts of produced α-LDx were increased depending on the ratio of synthesized α-1,3 linkages. In addition, approximately 80 % of the synthesized products were partially hydrolyzed by mammalian α-glucosidases, and the glucose generation rates decelerated as the amounts of α-1,3 linkages increased. In conclusion, new types of α-glucans with α-1,4 and α-1,3 linkages were successfully synthesized by a dual enzyme reaction. These can be utilized as slowly digestible and prebiotic ingredients in the gastrointestinal tract due to their novel linkage patterns and high molecular weights.

Production of highly branched α-limit dextrins with enhanced slow digestibility by various glycogen-branching enzymes

α-Limit dextrins (α-LDx) are slowly digestible carbohydrates that attenuate postprandial glycemic response and trigger the secretion of satiety-related hormones. In this study, more highly branched α-LDx were enzymatically synthesized to enhance the slowly digestible property by various origins of glycogen branching enzyme (GBE), which catalyzes the transglycosylation to form α-1,6 branching points after cleaving α-1,4 linkages. Results showed that the proportion of branched α-LDx in starch molecules increased around 2.2–8.1 % compared to α-LDx from starch without GBE treatment as the ratio of α-1,6 linkages increased after different types of GBE treatments. Furthermore, the enzymatic increment of branching points enhanced the slowly digestible properties of α-LDx at the mammalian α-glucosidase level by 17.3–28.5 %, although the rates of glucose generation were different depending on the source of GBE treatment. Thus, the highly branched α-LDx with a higher amount of α-1,6 linkages and a higher molecular weight can be applied as a functional ingredient to deliver glucose throughout the entire small intestine without a glycemic spike which has the potential to control metabolic diseases such as obesity and type 2 diabetes.

Lawsonia inermis flower aqueous extract expressed better anti-alpha-glucosidase and anti-acetylcholinesterase activity and their molecular dynamics

Lawsonia inermis (henna) has been used in traditional medicine throughout the world and biological property of its flower has been least explored. In the present study, the phytochemical characterization and biological activity (in vitro radical scavenging activity, anti-alpha glucosidase and anti-acetylcholinesterase) of aqueous extract prepared from henna flower (HFAE) was carried out by both Qualitative and quantitative phytochemical analysis and Fourier-transform infrared spectroscopy revealed the functional group of the phytoconstituents such as phenolics, flavonoids, saponin, tannins and glycosides. The phytochemicals present in HFAE was preliminary identified by liquid chromatography/electrospray ionization tandem mass spectrometry. The HFAE showed potent in vitro antioxidant activity and the HFAE inhibited mammalian α-glucosidase (IC50 = 129.1 ± 5.3 µg/ml; Ki = 38.92 µg/ml) and acetylcholinesterase (AChE; IC50 = 137.77 ± 3.5 µg/ml; Ki = 35.71 µg/ml) activity by competitive manner. In silico molecular docking analysis revealed the interaction of active constituents identified in HFAE with human α-glucosidase and AChE. Molecular dynamics simulation for 100 ns showed the stable binding of top two ligand/enzyme complexes with lowest binding energy such as 1,2,3,6-Tetrakis-O-galloyl-beta-D-glucose (TGBG)/human α-glucosidase, Kaempferol 3-glucoside-7-rhamnoside (KGR)/α-glucosidase, agrimonolide 6-O-β-D-glucopyranoside (AMLG)/human AChE and KGR/AChE. Through MM/GBSA analysis, the binding energy for TGBG/human α-glucosidase, KGR/α-glucosidase, AMLG/human AChE and KGR/AChE was found to be −46.3216, −28.5772, −45.0077 and −47.0956 kcal/mol, respectively. Altogether, HFAE showed an excellent antioxidant, anti-alpha glucosidase and anti-AChE activity under in vitro. This study suggest HFAE with remarkable biological activities could be further explored for therapeutics against type 2 diabetes and diabetes-associated cognitive decline.Communicated by Ramaswamy H. Sarma

A systematic review of the inhibitory effect of extracts from edible parts of nuts on α-glucosidase activity.

An elevated postprandial glycaemic response is a risk factor for developing type 2 diabetes mellitus (T2DM). Inhibition of digestive enzymes, including membrane-bound brush-border α-glucosidases, leads to slowed carbohydrate digestion and absorption, and reduced postprandial glycaemia. Nuts are eaten widely around the world, and have the potential to inhibit α-glucosidases through their content of polyphenols and other bioactive compounds. We set out to conduct a systematic literature review exploring the inhibitory effect of extracts from edible parts of various nuts on α-glucosidase activity in vitro to ensure, as far as possible, that no papers were missed. After an initial screening, 38 studies were reviewed in full, of which 15 were suitable for the present systematic review. Notably, no studies were found which tested the inhibitory potential of nut extracts against human α-glucosidases. Two studies showed that extracts from almonds and hazelnuts inhibited rat α-glucosidase activity, but the remaining papers reported data on the yeast α-glucosidase enzyme. Where yeast and rat enzymes can be compared, it is clear that nut extracts inhibit yeast α-glucosidase more strongly than mammalian α-glucosidase, which may lead to over-estimation when predicting effects in vivo when using data from the yeast enzyme. In contrast, acarbose is a stronger inhibitor of mammalian α-glucosidase compared to the yeast enzyme. Thus, although the present review indicates that extracts from nuts inhibit yeast α-glucosidase, this cannot be extrapolated to humans in vivo. There is some evidence that extracts from almonds and hazelnuts inhibit rat α-glucosidase, but no information on human enzyme sources. Since most work has been published on the yeast enzyme, future work in vitro must utilise mammalian, and preferably human, α-glucosidases in order to be relevant to human health and disease. This systematic review was registered at INPLASY as INPLASY202280061.

New insights suggest isomaltooligosaccharides are slowly digestible carbohydrates, rather than dietary fibers, at constitutive mammalian α-glucosidase levels

Isomaltooligosaccharides (IMOs) have been characterized as dietary fibers that resist digestion in the small intestine; however, previous studies suggested that various α-glycosidic linkages in IMOs were hydrolyzed by mammalian α-glucosidases. This study investigated the hydrolysis of IMOs by small intestinal α-glucosidases from rat and human recombinant sucrase–isomaltase complex compared to commonly used fungal amyloglucosidase (AMG) in vitro. Interestingly, mammalian α-glucosidases fully hydrolyzed various IMOs to glucose at a slow rate compared with linear maltooligosaccharides, whereas AMG could not fully hydrolyze IMOs because of its very low hydrolytic activity on α-1,6 linkages. This suggests that IMOs have been misjudged as prebiotic ingredients that bypass the small intestine due to the nature of the assay used. Instead, IMOs can be applied in the food industry as slowly digestible materials to regulate the glycemic response and energy delivery in the mammalian digestive system, rather than as dietary fibers.

Addition of 1, 4-α-glucan branching enzyme during the preparation of raw dough reduces the retrogradation and increases the slowly digestible fraction of starch in cooked noodles

Consumers significantly prefer wheat noodles that offer both an acceptable texture and health benefits. To this end, a cold-active 1,4-α-glucan branching enzyme from Bifidobacterium longum (BlBE) was expressed in the generally recognized as safe (GRAS) host cell Bacillus subtilis and then used at 120, 240 or 480 U/g flour in the preparation of raw dough. The storage modulus and loss modulus of the BlBE-modified dough decreased, but the pseudo-plasticity increased. The cooked noodles' hardness, gumminess and chewiness decreased by 12.1%–45.8%, 9.7%–40.4% and 16.0%–42.4%, respectively, but both resilience and cohesiveness increased by 4.0%–14.8% and 1.8%–9.0%, respectively. Pearson analysis revealed a correlation between the noodles' textural parameters and the doughs' power law equation parameters. BlBE-modified noodles exhibited significantly (P < 0.05) lower differential scanning calorimetry retrogradation enthalpies during storage at 4 °C for 7 days and released significantly lower levels of glucose during incubation with mammalian α-glucosidase at 37 °C for 10 min–360 min. BlBE at 480 U/g flour increased the slowly digestible portion by 12.6%. BlBE decreased the molecular weight, x-ray diffraction crystallinity, and fourier transform infrared spectroscopy ratio of band's heights at 1045 cm−1 and 1022 cm−1 of starch but increased the amylopectin content and ratio of short- to long-branch chains. These structural changes in starch partially explained the reduced retrogradation and enhanced slowly digestible starch fraction in the noodles.

Hypoglycemic activity of Codonopsis pilosula (Franch.) Nannf. in vitro and in vivo and its chemical composition identification by UPLC-Triple-TOF-MS/MS.

Codonopsis pilosula (Franch.) Nannf. (CPN), mainly planted in the northwest region, is a traditional Chinese medicine/good health food for nourishing qi and promoting blood circulation. This study firstly evaluated the inhibitory effects of the CPN extraction (CPNE) on α-glucosidase in vitro and in vivo, and tentatively confirmed its chemical ingredients by employing UHPLC-Triple-TOF-MS/MS. The CPNE had strong inhibitory activities against mammalian α-glucosidase (sucrase and maltase) and yeast α-glycosidase with semi-inhibitory concentrations (IC50) of 0.241 mg mL-1, 0.326 mg mL-1 and 1.167 mg mL-1, respectively. In addition, the CPNE could significantly decrease the postprandial blood glucose (PBG) levels in the sucrose/maltose/starch tolerance assays of diabetic mice. Furthermore, a total of 29 compounds, including 3 alkaloids, 13 phenolic acids, 8 alcohol glycosides and 5 alkynosides, were assigned based on comparison with the standards and references, as well as the analysis of main fragments. These results demonstrated that CPN could be used as an adjuvant therapy or dietary supplements to effectively control the occurrence and development of diabetes.

Critical Assessment of In Vitro Screening of α-Glucosidase Inhibitors from Plants with Acarbose as a Reference Standard.

Postprandial hyperglycemia is treated with the oral antidiabetic drug acarbose, an intestinal α-glucosidase inhibitor. Side effects of acarbose motivated a growing number of screening studies to identify novel α-glucosidase inhibitors derived from plant extracts and other natural sources. As "gold standard", acarbose is frequently included as the reference standard to assess the potency of these candidate α-glucosidase inhibitors, with many outperforming acarbose by several orders of magnitude. The results are subsequently used to identify suitable compounds/products with strong potential for in vivo efficacy. However, most α-glucosidase inhibitor screening studies use enzyme preparations obtained from nonmammalian sources (typically Saccharomyces cerevisiae), despite strong evidence that inhibition data obtained using nonmammalian α-glucosidase may hold limited value in terms of identifying α-glucosidase inhibitors with actual in vivo hypoglycemic potential. The aim was to critically discuss the screening of novel α-glucosidase inhibitors from plant sources, emphasizing inconsistencies and pitfalls, specifically where acarbose was included as the reference standard. An assessment of the available literature emphasized the cruciality of stating the biological source of α-glucosidase in such screening studies to allow for unambiguous and rational interpretation of the data. The review also highlights the lack of a universally adopted screening assay for novel α-glucosidase inhibitors and the commercial availability of a standardized preparation of mammalian α-glucosidase.

Development of an Optimized Drying Process for the Recovery of Bioactive Compounds from the Autumn Fruits of Berberis vulgaris L. and Crataegus monogyna Jacq.

Hot air drying has proven to be an efficient method to preserve specific edible plant materials with medicinal properties. This is a process involving chemical, physical, and biological changes in plant matrices. Understanding these processes will lead to an improvement in the yields of bioactive compounds. This study aims to optimize the drying process of two species’ fruits used in folk medicine, Berberis vulgaris and Crataegus monogyna. The optimized extracts’ antioxidant capacity was assessed using various assays, with the barberry extract showing very good activity (50.85, 30.98, and 302.45 mg TE/g dw for DPPH, TEAC, and FRAP assays, respectively). Both species exerted good fungal α-glucosidase inhibitory activity (IC50 = 0.34 and 0.56 mg/mL, respectively) but no activity on mammalian α-glucosidase. Additionally, this study identified and quantified the main bioactive compounds. The results presented herein are a breakthrough in industrializing this drying process. Additional studies are necessary to mechanistically understand the drying process involved in these plant materials.

Antibacterial, Antifungal, and Antidiabetic Effects of Leaf Extracts from Persea americana Mill. (Lauraceae)

Fruits and leaves of Persia americana are used in traditional medical practices. This study was carried out to determine the antibacterial, antifungal, and antidiabetic effects of the leaf extracts from P. americana. The antibacterial activities of the leaf extracts were evaluated against Klebsiella pneumoniae and Staphylococcus epidermidis while antifungal activities were determined against Candida albicans and Candida tropicalis. The antidiabetic potential of the extracts was determined against mammalian α-glucosidase in vitro. The broth microdilution method was used to investigate the antibacterial and antifungal susceptibility of the microbial strains towards the leaf extracts. S. epidermidis was the most susceptible microbe out of the tested microorganisms. The acetone extract was the most potent extract against S. epidermidis with a minimum inhibitory concentration (MIC) of 50 μg/mL. At 100 μg/mL, the ethanol:water extract 18% of K. pneumoniae cells remained viable. Cell viability after exposure to the dichloromethane (DCM) and methanol extracts was 28% against C. albicans and 8% against C. tropicalis, respectively. The DCM:methanol and acetone extracts caused membrane damage in S. epidermidis exhibited by protein leakage. Only the acetone extract effected nucleic acid leakage. Screening of extracts’ potential to inhibit the activity of α-glucosidase was carried out spectrophotometrically following the production of p-nitrophenol from p-nitrophenol-glucopyranoside (substrate) at a wavelength of 405 nm. Out of all the tested extracts, the methanolic extract showed the best inhibitory activity on α-glucosidase enzyme in a time-dependent and dose-dependent manner.KiandKinactvalues were found to be 1.4 mg/mL and 2.4 U/min, respectively, after incubation for 1 hour. It was concluded that the leaf extracts of P. americana contain phytochemicals with antibacterial, antifungal, and α-glucosidase inhibitory effects. Further studies are required for the identification of the active compounds in the leaf extracts responsible for these observed effects.

Physicochemical Stability of Enriched Phenolic Fractions of Cyclopia genistoides and ex vivo Bi-directional Permeability of Major Xanthones and Benzophenones.

Fractions of an ultrafiltered Cyclopia genistoides extract, respectively enriched in xanthones and benzophenones, were previously shown to inhibit mammalian α-glucosidase in vitro. The present study investigated ex vivo intestinal transport of these fractions, using excised porcine jejunal tissue, to determine whether the gut could be a predominant in vivo site of action. The major bioactive compounds, the xanthones (mangiferin, isomangiferin) and benzophenones (3-β-D-glucopyranosyliriflophenone, 3-β-D-glucopyranosyl-4-O-β-D-glucopyranosyliriflophenone) exhibited poor permeation in the absorptive direction with a relatively high efflux ratio (efflux ratio > 1). The efflux ratio of 3-β-D-glucopyranosyl-4-O-β-D-glucopyranosyliriflophenone (3.05) was similar to rhodamine 123 (2.99), a known substrate of intestinal P-glycoprotein 1 efflux transporters. Low epithelial membrane transport rates, coupled with efflux mechanisms, would effectively concentrate these bioactive compounds at the target site (gut lumen). Storage stability testing and moisture sorption assays of the xanthone-enriched fraction, benzophenone-enriched fraction, and ultrafiltered Cyclopia genistoides extract were performed to determine their susceptibility to physical and chemical degradation during storage. Hygroscopicity of the powders, indicated by moisture uptake, decreased in the order: benzophenone-enriched fraction (22.7%) > ultrafiltered Cyclopia genistoides extract (14.0%) > xanthone-enriched fraction (10.7%). 3-β-D-Glucopyranosylmaclurin, a minor benzophenone, was the least stable of the compounds, degrading faster in the benzophenone-enriched fraction than in ultrafiltered Cyclopia genistoides extract, suggesting that the ultrafiltered extract matrix may provide a degree of protection against chemical degradation. Compound degradation during 12 wk of storage at 40 °C in moisture-impermeable containers was best explained by first order reaction kinetics.

Isolation and characterization of an iridoid, Arbortristoside-C from Nyctanthes arbor-tristis Linn., a potential drug candidate for diabetes targeting α-glucosidase

Many parts of the plant Nyctanthes arbor-tristis Linn. are widely investigated for their biological properties. Purified Arbortristosides from seeds are reported as anticancer, anti-leishmania, anti-inflammatory, anti-allergic, immunomodulatory and antiviral. The present study elaborates on the isolation, structural and functional characterization of Arbortristoside-C and its inhibition properties against alpha-glucosidase, an important target for diabetes mellitus. Arbortristoside-C is purified from seeds of N. arbor-tristis by extraction using polar fractionation and chromatographic techniques. Arbortristoside-C has been characterized using Ultra Violet (UV), Mass (MS), Infra-Red (IR) and Nuclear Magnetic Resonance (NMR). Inhibition kinetics and Isothermal Titration Calorimetry (ITC) were used for activity and binding characteristics of acarbose and Arbortristoside-C using in-house purified α-glucosidase from Bos taurus. Modeling, docking and structural comparison with acarbose bound structure revealing the similar binding characteristics of Arbortristoside-C which include interaction with catalytic acid/base Aspartic acid residue. Cytotoxicity assay revealed that 100 µg/ml is the maximum toxic-free concentration of Arbortristoside-C. The purified Arbortristoside-C showed inhibition against mammalian α-glucosidase, suggesting its potential to treat Diabetes mellitus.

Highly branched α-limit dextrins attenuate the glycemic response and stimulate the secretion of satiety hormone peptide YY

Starch molecules are hydrolyzed to linear malto-oligosaccharides and branched α-limit dextrins (α-LDx) by salivary and pancreatic α-amylases in the gastrointestinal tract. In this study, we investigated the physiological responses to chromatographically purified branched α-LDx, which are slowly hydrolyzed owing to their high α-1,6 linkage ratios. Our results demonstrate that the digestion of branched α-LDx by mammalian α-glucosidases is slower than that of malto-oligosaccharides in vitro. In vivo experiments using mice showed that the glucose spike at the initial stage of α-LDx hydrolysis was significantly (p < 0.05) attenuated owing to an extended glycemic response. Branched α-LDx stimulated the secretion of peptide YY, which controls the satiety level and rate of gastric emptying by regulating the hypothalamus activity. In conclusion, the slow digestibility of branched α-LDx decelerated glucogenesis in vitro and in vivo; this phenomenon may result in beneficial physiological effects for regulate type 2 diabetes, obesity, and related chronic diseases by controlling post-prandial glucose homeostasis.

A bioactive polypeptide from sugarcane selectively inhibits intestinal sucrase

Human sucrase enzyme is a key therapeutic target for type 2 diabetes. While sugarcane sucrase inhibitor (sucinh) modulates invertase activity thereby accumulates sucrose. Molecular level understanding of sucinh towards mammalian α-glucosidases is scarce. The interaction of sucinh with human sucrase was identified and the association of these proteins was confirmed using co-purification, co-immunoprecipitation and pull-down assay. In addition, microscale thermophoresis assay showed that sucinh has a tight binding with sucrase (Kd = 4.77 nM) and a better affinity over acarbose. Collectively, in vitro, ex vivo and in silico data revealed that sucinh is selective for intestinal sucrase. The M region (H5/6 loop) of sucinh identified at the protein-protein interface is shown to have high affinity over N and C regions. Whereas, the biolayer luminescent imaging and microscale thermophoresis on the synthetic peptide of 28 amino acids of M region has a weak dose-dependent binding with sucrase. However, the synthetic peptide did not show substantial inhibition of sucrase and amylase activities at low concentration. Naturally derived carbohydrate mimics were shown to have a positive impact at the in vitro conditions. The insights obtained in this study give clues towards a new class of bioactive therapeutic peptides for α-glucosidases. A new horizon towards polypeptides derived from food sources emerge as a promising strategy for dietary interventions for prediabetic conditions.

Enzymatically elongated rice starches by amylosucrase from Deinococcus geothermalis lead to slow down the glucose generation rate at the mammalian α-glucosidase level

Amylosucrase (AS) catalyzes the transfer of a glucosyl unit from sucrose onto α-1,4-linked glucan polymers in starch. In this study, AS from Deinococcus geothermalis (DgAS) was applied to produce modified rice starches with slowly digestible properties. DgAS-treated waxy and normal rice starches showed significantly (p < 0.05) elevated degrees of polymerization, suggesting that the external chains were elongated. Additionally, the crystalline structures of starches changed from A- to B-type, and the temperature transition properties of enzymatically modified rice starches increased. The amounts of slowly digestible starch (SDS) increased remarkably (20.1% and 18.8%; waxy and normal rice starches, respectively), and the DgAS-treated rice starches were slowly hydrolyzed to glucose at the mammalian mucosal α-glucosidase level. Thus, DgAS-treated rice starches can be used to produce SDS-based ingredients that attenuate the glucose spike after glycemic food ingestion.