An alternative broad-specificity pathway for glycan breakdown in bacteria.

The vast majority of glycosidases characterized to date follow one of the variations of the 'Koshland' mechanisms1 to hydrolyse glycosidic bonds through substitution reactions. Here we describe a large-scale screen of a human gut microbiome metagenomic library using an assay that selectively identifies non-Koshland glycosidase activities2. Using this, we identify a cluster of enzymes with extremely broad substrate specificities and thoroughly characterize these, mechanistically and structurally. These enzymes not only break glycosidic linkages of both α and ß stereochemistry and multiple connectivities, but also cleave substrates that are not hydrolysed by standard glycosidases. These include thioglycosides, such as the glucosinolates from plants, and pseudoglycosidic bonds of pharmaceuticals such as acarbose. This is achieved through a distinct mechanism of hydrolysis that involves oxidation/reduction and elimination/hydration steps, each catalysed by enzyme modules that are in many cases interchangeable between organisms and substrate classes. Homologues of these enzymes occur in both Gram-positive and Gram-negative bacteria associated with the gut microbiome and other body parts, as well as other environments, such as soil and sea. Such alternative step-wise mechanisms appear to constitute largely unrecognized but abundant pathways for glycan degradation as part of the metabolism of carbohydrates in bacteria.

Studies on α-amylase inhibition by acarbose and quercetin using fluorescence, circular dichroism, docking, and dynamics simulations.

This study looked at the effects of acarbose (ACA) and quercetin (QUE) on α-amylase activity, employing QUE and ACA to measure enzyme activity. The study observed that both drugs suppressed α-amylase activity, with greater inhibition reported at higher concentrations. The use of tryptophan residues as an intrinsic fluorescence probe permitted the observation of conformational changes in α-amylase, with CD measurements utilized to explore the secondary structure in the presence of QUE and ACA. Docking studies revealed an effective interaction between α-amylase, quercetin and acarbose, with a higher binding energy. Finally, a trajectory analysis was done to establish the stability and volatility of these complexes. These findings have potential significance for the development of new α-amylase-related therapeutics.

In vitro inhibitory effect of five natural sweeteners on α-glucosidase and α-amylase.

A promising and efficacious approach to manage diabetes is inhibiting α-glucosidase and α-amylase activity. Therefore, the inhibitory activities of five natural sweeteners (mogrosides (Mog), stevioside (Ste), glycyrrhizinic acid (GA), crude trilobatin (CT), and crude rubusoside (CR)) against α-glucosidase and α-amylase and their interactions were evaluated in vitro using enzyme kinetics, fluorescence spectroscopy, Fourier infrared spectroscopy, and molecular docking. The inhibitor sequence was CT > GA > Ste, as GA competitively inhibited α-glycosidase activity while CT and Ste exhibited mixed inhibitory effects. Compared to a positive control acarbose, the inhibitory activity of CT was higher. For α-amylase, the mixed inhibitors CT, CR, and Mog and the competitive inhibitor Ste effectively inhibited the enzyme, with the following order: CT > CR > Ste > Mog; nevertheless, the inhibitors were slightly inferior to acarbose. Three-dimensional fluorescence spectra depicted that GA, CT, and CR bound to the hydrophobic cavity of α-glucosidase or α-amylase and changed the polarity of the hydrophobic amino acid-based microenvironment and structure of the polypeptide chain backbone. Infrared spectroscopy revealed that GA, CT, and CR could disrupt the secondary structure of α-glucosidase or α-amylase, which decreased enzyme activity. GA, trilobatin and rubusoside bound to amino acid residues through hydrogen bonds and hydrophobic interactions, changing the conformation of enzyme molecules to decrease the enzymatic activity. Thus, CT, CR and GA exhibit promising inhibitory effects against α-glucosidase and α-amylase.

Novel molecular hybrids of EGCG and quinoxaline: Potent multi-targeting antidiabetic agents that inhibit α-glucosidase, α-amylase, and oxidative stress.

Diabetes mellitus is a multifactorial disease and its effective therapy often demands several drugs with different modes of action. Herein, we report a rational design and synthesis of multi-targeting novel molecular hybrids comprised of EGCG and quinoxaline derivatives that can effectively inhibit α-glucosidase, α-amylase as well as control oxidative stress by scavenging ROS. The hybrids showed superior inhibition of α-glucosidase along with similar α-amylase inhibition as compared to standard drug, acarbose. Most potent compound, 15c showed an IC50 of 0.50 µM (IC50 of acarbose 190 µM) against α-glucosidase. Kinetics studies with 15c revealed a competitive inhibition against α-glucosidase. Binding affinity of 15c (-9.5 kcal/mol) towards α-glucosidase was significantly higher than acarbose (-7.7 kcal/mol). 15c exhibited remarkably high antioxidant activity (IC50 = 18.84 µM), much better than vitamin C (IC50 = 33.04 µM). Of note, acarbose shows no antioxidant activity. Furthermore, α-amylase activity was effectively inhibited by 15c with an IC50 value of 16.35 µM. No cytotoxicity was observed for 15c (up to 40 µM) in MCF-7 cells. Taken together, we report a series of multi-targeting molecular hybrids capable of inhibiting carbohydrate hydrolysing enzymes as well as reducing oxidative stress, thus representing an advancement towards effective and novel therapeutic approaches for diabetes.

Synergistic effect of potential alpha-amylase inhibitors from Egyptian propolis with acarbose using in silico and in vitro combination analysis.

BACKGROUND: Type 2 Diabetes mellitus (DM) is an affliction impacting the quality of life of millions of people worldwide. An approach used in the management of Type 2 DM involves the use of the carbohydrate-hydrolyzing enzyme inhibitor, acarbose. Although acarbose has long been the go-to drug in this key approach, it has become apparent that its side effects negatively impact patient adherence and subsequently, therapeutic outcomes. Similar to acarbose in its mechanism of action, bee propolis, a unique natural adhesive biomass consisting of biologically active metabolites, has been found to have antidiabetic potential through its inhibition of α-amylase. To minimize the need for ultimately novel agents while simultaneously aiming to decrease the side effects of acarbose and enhance its efficacy, combination drug therapy has become a promising pharmacotherapeutic strategy and a focal point of this study. METHODS: Computer-aided molecular docking and molecular dynamics (MD) simulations accompanied by in vitro testing were used to mine novel, pharmacologically active chemical entities from Egyptian propolis to combat Type 2 DM. Glide docking was utilized for a structure-based virtual screening of the largest in-house library of Egyptian propolis metabolites gathered from literature, in addition to GC-MS analysis of the propolis sample under investigation. Thereafter, combination analysis by means of fixed-ratio combinations of acarbose with propolis and the top chosen propolis-derived phytoligand was implemented. RESULTS: Aucubin, identified for the first time in propolis worldwide and kaempferol were the most promising virtual hits. Subsequent in vitro α-amylase inhibitory assay demonstrated the ability of these hits to significantly inhibit the enzyme in a dose-dependent manner with an IC50 of 2.37 ± 0.02 mM and 4.84 ± 0.14 mM, respectively. The binary combination of acarbose with each of propolis and kaempferol displayed maximal synergy at lower effect levels. Molecular docking and MD simulations revealed a cooperative binding mode between kaempferol and acarbose within the active site. CONCLUSION: The suggested strategy seems imperative to ensure a steady supply of new therapeutic entities sourced from Egyptian propolis to regress the development of DM. Further pharmacological in vivo investigations are required to confirm the potent antidiabetic potential of the studied combination.

Drug screening of α-amylase inhibitors as candidates for treating diabetes.

In the present study, the identification of potential α-amylase inhibitors is explored as a potential strategy for treating type-2 diabetes mellitus. A computationally driven approach using molecular docking was employed to search for new α-amylase inhibitors. The interactions of potential drugs with the enzyme's active site were investigated and compared with the contacts established by acarbose (a reference drug for α-amylase inhibition) in the crystallographic structure 1B2Y. For this active site characterization, both molecular docking and molecular dynamics simulations were performed, and the residues involved in the α-amylase-acarbose complex were considered to analyse the potential drug's interaction with the enzyme. Two potential α-amylase inhibitors (AN-153I105594 and AN-153I104845) have been selected following this computational strategy. Both compounds established a large number of interactions with key binding site α-amylase amino acids and obtained a comparable docking score concerning the reference drug (acarbose). Aiming to further analyse candidates' properties, their ADME (absorption, distribution, metabolism, excretion) parameters, druglikeness, organ toxicity, toxicological endpoints and median lethal dose (LD50 ) were estimated. Overall estimations are promising for both candidates, and in silico toxicity predictions suggest that a low toxicity should be expected.

Identifying the alpha-glucosidase inhibitory potential of dietary phytochemicals against diabetes mellitus type 2 via molecular interactions and dynamics simulation.

The research aims to identify the inhibitory potential of natural dietary phytochemicals against non-insulinotropic target protein alpha-glucosidase and its possible implications to diabetes mellitus type 2. A data set of sixteen plant-derived dietary molecules viz., 4,5-dimethyl-3-hydroxy-2(5H)-furanone, apigenin, bromelain, caffeic acid, cholecalciferol, dihydrokaempferol 7-o-glucopyranoside, galactomannan, genkwanin, isoimperatorin, luteolin, luteolin 7-o-glucoside, neohesperidin, oleanoic acid, pelargonidin-3-rutinoside, quercetin, and quinic acid were taken to accomplish molecular docking succeeded by their comparison with known inhibitors including acarbose, miglitol, voglibose, emiglitate, and 1-deoxynojirimycin. Among all phyto-compounds, bromelain (ΔG: -9.54 kcal/mol), cholecalciferol (-8.47 kcal/mol), luteolin (-9.02 kcal/mol), and neohesperidin (-8.53 kcal/mol) demonstrated better binding interactions with alpha-glucosidase in comparison to the best-known inhibitor, acarbose (ΔG: -7.93 kcal/mol). Molecular dynamics simulation of 10 ns duration, CYP450 site of metabolism identification, and prediction of activity spectra for substances depicted the bromelain as the most stable inhibitor compared to luteolin and acarbose. Findings of molecular interactions, molecular dynamics study, metabolism, and biological activity prediction proved bromelain as a potential alpha-glucosidase inhibitor. Thus, bromelain might be helpful as an insulin-independent therapeutic molecule towards controlling and managing diabetes mellitus type 2.

Isolated compounds from Dracaena angustifolia Roxb and acarbose synergistically/additively inhibit α-glucosidase and α-amylase: an in vitro study.

BACKGROUND: As a traditional herbal medicine, Dracaena angustifolia Roxb has been used as an anti-inflammatory agent by the Li people in Hainan, China. In preliminary phytochemical studies conducted in our lab, its fractions were found to inhibit α-glucosidase in vitro, indicating a potential for alleviating glucose dysregulation. METHODS: Through in vitro enzymatic assays, the abilities of the separated components to affect α-glucosidase and α-amylase were evaluated. By establishing concentration gradients and generating Lineweaver-Burk plots, the corresponding inhibition modes together with kinetic parameters were assessed. Following the evaluation of the outcomes of their combination with acarbose, computational docking and molecular dynamic simulations were carried out to analyse the interaction mechanisms and perform virtual screening against human enzymes. RESULTS: Compared with acarbose, 7 compounds, including flavonoid derivatives, amides and aromatic derivatives, with higher α-glucosidase inhibitory efficiencies were confirmed. It was found that those competitive/mixed candidates and acarbose interacted synergistically or additively on α-glucosidase. Moreover, 3 of them were able to inhibit α-amylase in mixed mode, and additive effects were observed in combination with acarbose. Through in silico docking, it was found that the active site residues as well as adjacent residues were involved in α-glucosidase and α-amylase binding, which were mainly achieved through hydrogen bonding. Among those dual-function flavonoids, Compound 9 was predicted to be a considerable inhibitor of human enzymes, as the formation of ligand-enzyme complexes was mediated by the residues responsible for substrate recognition and catalysis, the stabilities of which were reiterated by molecular dynamics simulations. CONCLUSION: Despite their mild effects on α-amylase, considerable α-glucosidase inhibitory efficiencies and potential synergy with acarbose were exhibited by these natural candidates. Furthermore, a stable ligand, human α-glucosidase, was predicted by the performed simulations, which provided useful information for the application of Dracaena angustifolia Roxb in diabetes treatment.

Pharmacokinetics and drug-likeness of antidiabetic flavonoids: Molecular docking and DFT study.

Computer aided toxicity and pharmacokinetic prediction studies attracted the attention of pharmaceutical industries as an alternative means to predict potential drug candidates. In the present study, in-silico pharmacokinetic properties (ADME), drug-likeness, toxicity profiles of sixteen antidiabetic flavonoids that have ideal bidentate chelating sites for metal ion coordination were examined using SwissADME, Pro Tox II, vNN and ADMETlab web tools. Density functional theory (DFT) calculations were also employed to calculate quantum chemical descriptors of the compounds. Molecular docking studies against human alpha amylase were also conducted. The results were compared with the control drugs, metformin and acarbose. The drug-likeness prediction results showed that all flavonoids, except myricetin, were found to obey Lipinski's rule of five for their drug like molecular nature. Pharmacokinetically, chrysin, wogonin, genistein, baicalein, and apigenin showed best absorption profile with human intestinal absorption (HIA) value of ≥ 30%, compared to the other flavonoids. Baicalein, butein, ellagic acid, eriodyctiol, Fisetin and quercetin were predicted to show carcinogenicity. The flavonoid derivatives considered in this study are predicted to be suitable molecules for CYP3A probes, except eriodyctiol which interacts with P-glycoprotein (p-gp). The toxicological endpoints prediction analysis showed that the median lethal dose (LD50) values range from 159-3919 mg/Kg, of which baicalein and quercetin are found to be mutagenic whereas butein is found to be the only immunotoxin. Molecular docking studies showed that the significant interaction (-7.5 to -8.3 kcal/mol) of the studied molecules in the binding pocket of the α-amylase protein relative to the control metformin with the crucial amino acids Asp 197, Glu 233, Asp 197, Glu 233, Trp 59, Tyr 62, His 101, Leu 162, Arg 195, His 299 and Leu 165. Chrysin was predicted to be a ligand with high absorption and lipophilicity with 84.6% absorption compared to metformin (78.3%). Moreover, quantum chemical, ADMET, drug-likeness and molecular docking profiles predicted that chrysin is a good bidentate ligand.

Synthesis and α-glucosidase inhibition studies of norfloxacin-acetanilide hybrids.

α-Glucosidase inhibitors occupy a prominent position among the various treatments of type-2 diabetes mellitus (DM2). In this study, a series of new norfloxacin-acetanilide hybrid molecules were synthesized and screened for α-glucosidase inhibition activity. The synthetic methodology involves the synthesis of a series of α-bromoacetanilides by condensing bromoacetyl bromide with various substituted anilines. These α-bromoacetanilides were coupled with norfloxacin in DMF to get the titled hybrids. The structure elucidation of synthesized compounds were characterized by 1H NMR, 13C NMR and LC-MS. Finally, the compounds were screened for their α-glucosidase inhibition activity using acarbose as a reference drug (IC50 =58 µM). Among the tested compounds, 3i and 3j displayed potent α-glucosidase inhibition activity with IC50 values of 7.81±0.038 and 5.55±0.012 µM respectively. In-addition, 3m, 3f and 3k were demonstrated moderate alpha-glucosidase inhibition activities with IC50 values of 52.905±0.041, 23.79± 0.087 and 23.06±0.026 µM respectively. The structure-activity relationship was established with the help of molecular docking by using Molecular Operating Environment software (MOE 2014).

Synthesis and in vitro evaluation of chlorogenic acid amides as potential hypoglycemic agents and their synergistic effect with acarbose.

Type 2 Diabetes mellitus is a chronic disease considered one of the most severe global health emergencies. Chlorogenic acid (1) has been shown to delay intestinal glucose absorption by inhibiting the activity of α-glucosidase (α-Glu) and α-amylase (α-Amy). In the present work, eleven chlorogenic acid amides have been synthesized and evaluated for their antioxidant properties (as DPPH and ORAC) and inhibition activity towards the two enzymes and, with the aim to obtain dual-action antidiabetic agents. The two most promising hypoglycemic compounds, bearing a tertiary amine function on an alkyl chain (8) and a benzothiazole scaffold (11), showed IC50 values lower than that of (1) (45.5 µM α-Glu; 105.2 µM α-Amy). Amides 8 and 11 were by far more potent α-Glu inhibitors than the antidiabetic drug acarbose (IC50 = 268.4 µM) and about twice less active toward α-Amy than acarbose (IC50 = 34.4 µM). Kinetics experiments on amides 8 and 11 indicated these compounds as mixed-type inhibitors of α-Glu with K'i values of 13.3 and 6.3 µM, respectively. The amylase inhibition occurred with a competitive mechanism in the presence of 8 (Ki = 79.7 µM) and with a mixed-type mechanism with 11 (Ki = 19.1 µM; K'i = 93.6 µM). Molecular docking analyses supported these results, highlighting the presence of additional binding sites in both enzymes. Fluorescence experiments confirmed the grater affinity of amides 8 and 11 towards the two enzymes respect to (1). Moreover, a significant enhancement in acarbose efficacy was observed when inhibition assays were performed adding acarbose and amide 11. The above outcomes pinpointed the benzothiazole-based amide 11 as a promising candidate for further studies on type 2 diabetes treatment, both alone or combined with acarbose.

Utilization of Cassava Wastewater for Low-Cost Production of Prodigiosin via Serratia marcescens TNU01 Fermentation and Its Novel Potent α-Glucosidase Inhibitory Effect.

The purpose of this study was to reuse cassava wastewater (CW) for scaled-up production, via the fermentation of prodigiosin (PG), and to conduct an evaluation of its bioactivities. PG was produced at the yield of high 6150 mg/L in a 14 L-bioreactor system, when the designed novel medium (7 L), containing CW and supplemented with 0.25% casein, 0.05% MgSO4, and 0.1% K2HPO4, was fermented with Serratia marcescens TNU01 at 28 °C in 8 h. The PG produced and purified in this study was assayed for some medical effects and showed moderate antioxidant, high anti-NO (anti-nitric oxide), and potential α-glucosidase inhibitory activities. Notably, PG was first reported as a novel effective α-glucosidase inhibitor with a low IC50 value of 0.0183 µg/mL. The commercial anti-diabetic drug acarbose was tested for comparison and had a lesser effect with a high IC50 value of 328.4 µg/mL, respectively. In a docking study, the cation form of PG (cation-PG) was found to bind to the enzyme α-glucosidase by interacting with two prominent amino acids, ASP568 and PHE601, at the binding site on the target enzyme, creating six linkages and showing a better binding energy score (-14.6 kcal/mol) than acarbose (-10.5 kcal/mol). The results of this work suggest that cassava wastewater can serve as a low-cost raw material for the effective production of PG, a potential antidiabetic drug candidate.

In vitro and in silico studies of bis (indol-3-yl) methane derivatives as potential α-glucosidase and α-amylase inhibitors.

In this paper, bis (indol-3-yl) methanes (BIMs) were synthesised and evaluated for their inhibitory activity against α-glucosidase and α-amylase. All synthesised compounds showed potential α-glucosidase and α-amylase inhibitory activities. Compounds 5 g (IC50: 7.54 ± 1.10 µM), 5e (IC50: 9.00 ± 0.97 µM), and 5 h (IC50: 9.57 ± 0.62 µM) presented strongest inhibitory activities against α-glucosidase, that were ∼ 30 times stronger than acarbose. Compounds 5 g (IC50: 32.18 ± 1.66 µM), 5 h (IC50: 31.47 ± 1.42 µM), and 5 s (IC50: 30.91 ± 0.86 µM) showed strongest inhibitory activities towards α-amylase, ∼ 2.5 times stronger than acarbose. The mechanisms and docking simulation of the compounds were also studied. Compounds 5 g and 5 h exhibited bifunctional inhibitory activity against these two enzymes. Furthermore, compounds showed no toxicity against 3T3-L1 cells and HepG2 cells.HighlightsA series of bis (indol-3-yl) methanes (BIMs) were synthesised and evaluated inhibitory activities against α-glucosidase and α-amylase.Compound 5g exhibited promising activity (IC50 = 7.54 ± 1.10 µM) against α-glucosidase.Compound 5s exhibited promising activity (IC50 = 30.91 ± 0.86 µM) against α-amylase.In silico studies were performed to confirm the binding interactions of synthetic compounds with the enzyme active site.

Personal Glucose Meter for α-Glucosidase Inhibitor Screening Based on the Hydrolysis of Maltose.

As a key enzyme regulating postprandial blood glucose, α-Glucosidase is considered to be an effective target for the treatment of diabetes mellitus. In this study, a simple, rapid, and effective method for enzyme inhibitors screening assay was established based on α-glucosidase catalyzes reactions in a personal glucose meter (PGM). α-glucosidase catalyzes the hydrolysis of maltose to produce glucose, which triggers the reduction of ferricyanide (K3[Fe(CN)6]) to ferrocyanide (K4[Fe(CN)6]) and generates the PGM detectable signals. When the α-glucosidase inhibitor (such as acarbose) is added, the yield of glucose and the readout of PGM decreased accordingly. This method can achieve the direct determination of α-glucosidase activity by the PGM as simple as the blood glucose tests. Under the optimal experimental conditions, the developed method was applied to evaluate the inhibitory activity of thirty-four small-molecule compounds and eighteen medicinal plants extracts on α-glucosidase. The results exhibit that lithospermic acid (52.5 ± 3.0%) and protocatechualdehyde (36.8 ± 2.8%) have higher inhibitory activity than that of positive control acarbose (31.5 ± 2.5%) at the same final concentration of 5.0 mM. Besides, the lemon extract has a good inhibitory effect on α-glucosidase with a percentage of inhibition of 43.3 ± 3.5%. Finally, the binding sites and modes of four active small-molecule compounds to α-glucosidase were investigated by molecular docking analysis. These results indicate that the PGM method is feasible to screening inhibitors from natural products with simple and rapid operations.

Alpha-amylase as molecular target for treatment of diabetes mellitus: A comprehensive review.

The alpha (α)-amylase is a calcium metalloenzyme that aids digestion by breaking down polysaccharide molecules into smaller ones such as glucose and maltose. In addition, the enzyme causes postprandial hyperglycaemia and blood glucose levels to rise. α-Amylase is a well-known therapeutic target for the treatment and maintenance of postprandial blood glucose elevations. Various enzymatic inhibitors, such as acarbose, miglitol and voglibose, have been found to be effective in targeting this enzyme, prompting researchers to express an interest in developing potent alpha-amylase inhibitor molecules. The review mainly focused on designing different derivatives of drug molecules such as benzofuran hydrazone, indole hydrazone, spiroindolone, benzotriazoles, 1,3-diaryl-3-(arylamino) propan-1-one, oxadiazole and flavonoids along with their target-receptor interactions, IC50 values and other biological activities.

Redox-induced target-dependent ratiometric fluorescence sensing strategy and logic gate operation for detection of α-glucosidase activity and its inhibitor.

A target-dependent ratiometric fluorescence sensing strategy was designed and fabricated based on a redox reaction for highly sensitive detection of α-glucosidase (α-Glu) activity and its inhibitor. In this study, silicon quantum dots (SiQDs) with excellent optical properties and two-dimensional (2D) cobalt oxyhydroxide (CoOOH) nanosheets were successfully prepared and exploited for the detection of analytes. The CoOOH nanosheets are able to oxidize o-phenylenediamine (OPD), and the product 2,3-diaminophenazine (oxOPD) not only quenches the blue fluorescence of SiQDs (440 nm) by the inner filter effect (IFE) but also emits orange fluorescence (565 nm). α-Glu can catalytically hydrolyze l-ascorbic acid-2-O-α-d-glucopyranosyl (AA2G) to produce ascorbic acid (AA). The redox between AA and CoOOH could lead to the damage of CoOOH nanosheets, thereby inhibiting the oxidization of OPD and effectively preserving the fluorescence of SiQDs. Thus, ratiometric detection of α-Glu activity was achieved according to the AA-dependent dual-fluorescence signal responses. Under the optimal conditions, good linearity was obtained in the range of 0.01-6 U mL-1 with a detection limit of 0.004 U mL-1. The IC50 of α-Glu inhibitor acarbose was estimated to be 0.216 µM. The method provides high sensitivity and selectivity for the determination of α-Glu activity and its inhibitor, which has great application potential in clinical diagnosis and anti-diabetic drug screening. Furthermore, a logic gate analytical device was successfully established based on double fluorescence signals, which makes it possible to monitor α-Glu activity by intelligence equipment.

Comparative study of inhibition mechanisms of structurally different flavonoid compounds on α-glucosidase and synergistic effect with acarbose.

Flavonoid compounds have anti-diabetic activity, which can control blood glucose levels by inhibiting α-glucosidase activity. In this paper, the inhibition mechanisms between four flavonoid compounds and α-glucosidase were studied by multispectroscopic methods and molecular docking. The results showed that the inhibitory activities of flavonoid compounds were higher than that of acarbose, and the sequence of inhibition effect was scutellarein > nepetin > apigenin > hispidulin > acarbose. Also, the synergistic effects of flavonoid compounds combined with acarbose on inhibiting α-glucosidase activity were observed. The fluorescence results showed that flavonoid compounds combined with α-glucosidase to form a stable complex. And the spectral analysis indicated that the microenvironmental and secondary structure of α-glucosidase were changed. The present study demonstrated that the molecular structure of flavonoid compounds played an important role in the inhibition process, namely, scutellarein with more hydroxyl groups on the A-ring might serve as the most effective α-glucosidase inhibitor.

Synthesis, α-Glucosidase inhibition and molecular docking studies of tyrosol derivatives.

To find a potent α-glucosidase inhibitor, 24 tyrosol derivatives with different substituents located at the meta, ortho, or para position of the phenyl group have been synthesised via the Mitsunobu reaction, characterised by 1H NMR, 13C NMR, ESI-MS and IR and evaluated for inhibition. The derivatives possessed varying degrees of in vitro inhibitory activity against α-glucosidase and a relationship between the structure and activity was subsequently established for all compounds. Two of these compounds with substituents at the para position showed significant inhibitory effects surpassing that of the control standard acarbose. Molecular docking studies performed to better understand the binding interactions between the enzyme and the two most active compounds showed substantial binding within the active site of α-glucosidase. Taken together, these results indicate that the position of the substituent plays a crucial role in this inhibition and may facilitate the development of new α-glucosidase inhibitors.

Structure-based design of human pancreatic amylase inhibitors from the natural anthocyanin database for type 2 diabetes.

Human Pancreatic Amylase (HPA) is an important target for prevention and treatment of type 2 diabetes. Acarbose is a currently available drug acting as a HPA inhibitor, but its gastrointestinal side-effects cannot be neglected. Thus, developing novel HPA inhibitors with no side-effects is of great importance. Herein, we adopted a structure-based design approach and discovered a potent HPA inhibitor, malvidin 3-O-arabinoside (M3A), from the natural anthocyanin database. We identified M3A as an effective HPA inhibitor through virtual screening, enzyme activity and enzyme kinetic assays. We reported the structure and activity relationships as both the anthocyanidin core and glucosyl group affected the HPA inhibitory effect of anthocyanins. Molecular dynamics studies indicated that the HPA inhibition of M3A occurred via its binding to the HPA key catalytic residues Arg195 and Asp197 through stable hydrogen bonding. In addition, M3A was found to reduce α-helix fractions and increase ß-sheet fractions in CD spectrometry. Further in vivo studies showed that M3A significantly ameliorated the postprandial blood glucose level. Taken together, our results provide new insights into the development of novel HPA inhibitors from natural sources as food supplements for type 2 diabetes.

Hydrophilic Interaction Chromatography Coupled with Charged Aerosol Detection for Simultaneous Quantitation of Carbohydrates, Polyols and Ions in Food and Beverages.

Here, we report an accurate and versatile method for the simultaneous determination of 17 sugars (arabinose, erythrose, fructose, galactose, glucose, isomaltulose, lactose, lyxose, maltose, maltotriose, mannose, raffinose, rhamnose, ribose, sucrose, sorbose and xylose), seven polyols (erythritol, inositol, lactitol, maltitol, mannitol, sorbitol and xylitol), five ions (K+, Br-, Cl-, NO3- and SO42-) and the pseudosaccharide acarbose. For compound separation, hydrophilic interaction chromatography (HILIC) coupled to a corona charged aerosol detector (CAD) was used. The method was validated for linearity, precision, reproducibility, retention factor and optimal injection volume. Standards were measured in the range of 1-1000 mg L-1 and showed good intraday and interday repeatability, as well as precision (relative standard deviation (RSD) < 5%). The LODs and LOQs for the 30 analytes were in the range of 0.032-2.675 mg L-1 and 0.107-8.918 mg L-1, respectively. This method exhibited correlation coefficients of at least R2 > 0.97 for all analytes. The method was tested in 24 food and beverage samples to validate the separation efficiency and sensitivity in natural food matrices and to show the practicability of its use for routine food analysis.