Synthesis,Antidiabetic and Antitubercular Evaluation of Quinoline-pyrazolopyrimidine hybrids and Quinoline-4-Arylamines

Two libraries of quinoline-based hybrids 1-(7-chloroquinolin-4-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine and 7-chloro-N-phenylquinolin-4-amine were synthesized and evaluated for their α-glucosidase inhibitory and antioxidant properties. Compounds with 4-methylpiperidine and para-trifluoromethoxy groups, respectively, showed the most promising α-glucosidase inhibition activity with IC50 =46.70 and 40.84 μM, compared to the reference inhibitor, acarbose (IC50 =51.73 μM). Structure-activity relationship analysis suggested that the cyclic secondary amine pendants and para-phenyl substituents account for the variable enzyme inhibition. Antioxidant profiling further revealed that compounds with an N-methylpiperazine and N-ethylpiperazine ring, respectively, have good DPPH scavenging abilities with IC50 =0.18, 0.58 and 0.93 mM, as compared to ascorbic acid (IC50 =0.05 mM), while the best DPPH scavenger is NO2 -substituted compound (IC50 =0.08 mM). Also, compound with N-(2-hydroxyethyl)piperazine moiety emerged as the best NO radical scavenger with IC50 =0.28 mM. Molecular docking studies showed that the present compounds are orthosteric inhibitors with their quinoline, pyrimidine, and 4-amino units as crucial pharmacophores furnishing α-glucosidase binding at the catalytic site. Taken together, these compounds exhibit dual potentials; i. e., potent α-glucosidase inhibitors and excellent free radical scavengers. Hence, they may serve as structural templates in the search for agents to manage Type 2 diabetes mellitus. Finally, in preliminary assays investigating the anti-tubercular potential of these compounds, two pyrazolopyrimidine series compounds and a 7-chloro-N-phenylquinolin-4-amine hybrid showed sub-10 μM whole-cell activities against Mycobacterium tuberculosis.

Carbonylbis(hydrazine-1-carbothioamide) derivatives as a new class of α-glucosidase inhibitors and their mechanistic insights via molecular docking and dynamic simulations

In the past, efforts have been made to find a cure for diabetes, mainly evaluating new classes of compounds to explore their potency. In this study, we present the synthesis and evaluation of carbonylbis(hydrazine-1-carbothioamide) derivatives as potential α-glucosidase inhibitors, employing both in vivo and in silico investigations. The in vitro experiments revealed that all tested compounds were significantly potent for α-glucosidase inhibition, with the lead compound 3a displaying approximately 80 times higher activity than acarbose. To delve deeper, in silico induced fit docking, pharmacokinetics, and molecular dynamics studies were conducted. Significantly, compound 3a exhibited a docking score of -7.87 kcal/mol, surpassing acarbose, which had a docking score of -6.59 kcal/mol. The in silico ADMET indicated that most of the synthesized compounds have properties conducive to drug development. Molecular dynamics analysis demonstrated that, when the ligand 3a was coupled with the target 3TOP, Cα-RMSD backbone RMSD values below 2.4 Å and "Lig_fit_Prot" values below 2.7 Å were observed. QSAR analysis demonstrates that the "fOC8A" descriptor positively correlates with α-glucosidase inhibition activity, while "lipoplus_AbSA" positively contributes and "notringC_notringO_8B" negatively contributes to this activity.

Transient Hemichorea-hemiballism Induced by a Combination of Postprandial Hypotension and Severe Stenosis of the Innominate Artery Concomitant with Left Carotid Occlusion

Hemichorea-hemiballism (HCHB) due to transient ischemic attacks (TIAs) is rare. An 83-year-old woman had repeated episodes of right-sided HCHB for 3 months. Magnetic resonance (MR) angiography demonstrated occlusion of the left carotid and middle cerebral arteries and severe stenosis of the innominate artery, and 24-hour ambulatory blood pressure monitoring showed a blood pressure decrease of >20 mmHg after each meal. We speculated that HCHB developed as TIAs due to hemodynamic failure in the left cerebral hemisphere, caused by a combination of severe stenosis of the innominate artery concomitant with occlusion of the left carotid and middle cerebral arteries as well as postprandial hypotension.

Discovery of N-(phenylsulfonyl)thiazole-2-carboxamides as potent α-glucosidase inhibitors

In a search for novel nonsugar α-glucosidase inhibitors for diabetes treatment, a series of N-(phenylsulfonyl)thiazole-2-carboxamide derivatives were designed and synthesized, the α-glucosidase inhibitory activities were then evaluated. Several compounds with promising α-glucosidase inhibitory effects were identified. Among these, compound W24 which shows low cytotoxicity and good α-glucosidase inhibitory activity with an IC50 value of 53.0 ± 7.7 μM, is more competitive compared with the commercially available drug acarbose (IC50  = 228.3 ± 9.2 μM). W24 was identified as a promising candidate in the development of α-glucosidase inhibitors. Molecular docking studies and molecular dynamics simulation were also performed to reveal the binding pattern of the active compound to α-glucosidase, and the binding free energy of the best compound W24 was 36.3403 ± 3.91 kcal/mol.

Synthesis, in vitro Α-Glucosidase, and acetylcholinesterase inhibitory activities of novel Indol-Fused Pyrano[2,3-D]Pyrimidine compounds

In this study, new indol-fused pyrano[2,3-d]pyrimidines were designed and synthesized. These products were obtained in moderate to good yields and their structures were assigned by NMR, MS, and IR analysis. Afterwards, the biological important of the products was highlighted by evaluating in vitro for α-glucosidase inhibitory activity as well as acetylcholinesterase (AChE) inhibitory activity. Eleven products revealed substantial inhibitory activity against α-glucosidase enzyme, among which, two most potent products 11d,e were approximately 93-fold more potent than acarbose as a standard antidiabetic drug. Besides that, product 11k exhibited good AChE inhibition. The substituents on the 5-phenyl ring, attached to the pyran ring, played a critical role in inhibitory activities. The biological potencies have provided an opportunity to further investigations of indol-fused pyrano[2,3-d]pyrimidines as potential anti-diabetic agents.

Synthesis of new bis(dimethylamino)benzophenone hydrazone for diabetic management: In-vitro and in-silico approach

Inhibiting α-glucosidase is a reliable method for reducing blood sugar levels in diabetic individuals. Bis(dimethylamino)benzophenone derivatives 1-27 were synthesized from bis(dimethylamino)benzophenone via two-step reaction. Different spectroscopic techniques, including EI-MS and 1H NMR, were employed to characterize all synthetic derivatives. The elemental composition of synthetic compounds was confirmed by elemental analysis and results were found in agreement with the calculated values. The synthetic compounds 1-27 were evaluated for α-glucosidase inhibitory activity, except five compounds all derivatives showed good to moderate inhibitory potential in the range of IC50 = 0.28 ± 2.65 - 0.94 ± 2.20 μM. Among them, the most active compounds were 5, 8, 9, and 12 with IC50 values of 0.29 ± 4.63, 0.29 ± 0.93, 0.28 ± 3.65, and 0.28 ± 2.65, respectively. Furthermore, all these compounds were found to be non-toxic on human fibroblast cell lines (BJ cell lines). Kinetics study of compounds 8 and 9 revealed competitive type of inhibition with Ki values 2.79 ± 0.011 and 3.64 ± 0.012 μM, respectively. The binding interactions of synthetic compounds were also confirmed through molecular docking studies that indicated that compounds fit well in the active site of enzyme. Furthermore, a total of 30ns MD simulation was carried out for the most potent complexes of the series. The molecular dynamics study revealed that compound-8 and compound-12 were stable during the MD simulation.

Inhibitory effect of gallic acid from Thunbergia mysorensis against α-glucosidase, α-amylase, aldose reductase and their interaction: Inhibition kinetics and molecular simulations

In this exploration, we assessed the antihyperglycaemic properties of methanol extract of flowers of Thunbergia mysorensis (MeT) against α-glucosidase, α-amylase and aldose reductase enzymes for the effective management of postprandial hyperglycemia. Hyperglycemia occurs when the body lacks enough insulin or is unable to correctly utilize it. MeT inhibited both the carbohydrate digestive enzymes (α-glucosidase and α-amylase) and aldose reductase, which are vital for the therapeutic control of postprandial hyperglycaemia. MeT was also found to have significant antioxidant activity. Using several spectroscopic approaches, the primary active component found in MeT was identified as gallic acid. With low Ki values, gallic acid significantly inhibited α-glucosidase (30.86 µg/mL) and α-amylase (6.50 µg/mL). Also, MeT and gallic acid both inhibited aldose reductase effectively, corresponding to an IC50 value of 3.31 and 3.05 µg/mL. Our findings imply that the presence of polyphenol compounds (identified via HPLC analysis) is more likely to be responsible for the antihyperglycaemic role exhibited by MeT via the inhibition of α-glucosidase and the polyol pathway. Further, gallic acid interacted with the key residues of the active sites of α-glucosidase (-6.4 kcal/mol), α-amylase (-5.8 kcal/mol) and aldose reductase (-5.8 kcal/mol) as observed in the protein-ligand docking. It was also predicted that gallic acid was stable inside the binding pockets of the target enzymes during molecular dynamics simulation. Overall, gallic acid derived from MeT via bioassay-guided isolation emerges as a natural antidiabetic drug and can be taken into in vivo and clinical studies shortly.Communicated by Ramaswamy H. Sarma.

Recent Progress on Natural α-glucosidase Inhibitors Derived from the Plants and Microorganisms

α-Glucosidase inhibitors (AGIs) showcase versatile biochemical activities with respect to antidiabetic, anticancerous, antiobese and antiviral effects. They have drawn a great deal of attention from the scientific community. While α-glucosidase inhibitors are mostly discovered from plants and microorganisms, the recent advance in natural αglucosidase inhibitors over the past five years has been reviewed in this article, and 139 distinct α-glucosidase inhibitors from the plants and microorganisms were classified into ten groups based on their chemical structures, including flavonoids (34), xanthones (6), alkaloids (8), benzopyrones / benzofuranones (8), terpenes (23), saponins (8), phenols / alcohols (25), esters (18), chalcone (5) and other compounds (4). In this review, we mainly focused on the novel chemical structures and the various biological activities of theses natural AGIs. Some of the selected natural compounds exhibit powerful α-glucosidase inhibitory activity and anti-tumor activity, may hold promise to become the candidate drugs for treating type II diabetes and cancer in future.

Pneumatosis intestinalis associated with α-glucosidase inhibitors: a pharmacovigilance study of the FDA adverse event reporting system from 2004 to 2022

BACKGROUND

A-glucosidase inhibitors (AGIs) are suitable for type 2 diabetes mellitus patients with carbohydrate-rich diets while were reported associated with the rare but potentially life-threatening pneumatosis intestinalis (PI).

RESEARCH DESIGN AND METHODS

Data from the US Food and Drug Administration Adverse Event Reporting System (FAERS) were examined for AGIs, acarbose, voglibose, miglitol, or other anti-hyperglycemic drug classes. The reporting odds ratio (ROR), proportional reporting ratio, gamma poisson shrinker, and bayesian confidence propagation neural network were applied to determine the safety signals, which were performed under two other models to control for bias from type 2 diabetes mellitus and other anti-hyperglycemic drugs.

RESULTS

We found a significantly higher reporting of PI in all AGIs group [ROR = 73.85 (61.56-88.58)]. When further subdivided, voglibose and miglitol had a larger ROR than acarbose whether models were adjusted or not. The safety signals of biguanides, sulfonylureas, thiazolidinediones, dipeptidyl peptidase 4 inhibitors inhibitors, glucagon-like peptide-1 receptor agonists, sodium-glucose co-transporter-2 inhibitors, and other drug classes were not detected in three models.

CONCLUSIONS

Our study identified the safety signals of the PI-AGIs pair, primarily based on disproportionality analysis while controlling for confounders such as the disease-associated risk of PI and concomitant drug exposure.

Diphenyl-substituted triazine derivatives: synthesis, α-glucosidase inhibitory activity, kinetics and in silico studies

Background: Diabetes mellitus (DM) is a chronic disorder, considered to be a major global health challenge in the 21st century. α-Glucosidase enzyme is a well-known drug target to treat Type II DM. Methods: A new library of biphenyl-substituted triazines was synthesized and confirmed by various spectroscopic techniques. Results: All compounds showed potent α-glucosidase inhibitory activity, with IC50 values ranging from 35.35 ± 0.34 to 564.41 ± 0.91 μM, as the standard acarbose, IC50 value of 750.7 ± 0.13 μM. Our in silico study has predicted key interactions with the enzyme's active site. Drug-likeness and absorption, distribution, metabolism, excretion and toxicity were also studied. Conclusion: This study has identified a range of potential hits against the α-glucosidase enzyme that may serve as antidiabetic agents after further investigations.

Evaluation of α-Glucosidase Inhibition and Antihyperglycemic Activity of Extracts Obtained from Leaves and Flowers of Rumex crispus L

Among antihyperglycemic drugs used for treating diabetes, α-glucosidase inhibitors generate the least adverse effects. This contribution aimed to evaluate the potential antidiabetic activity of Rumex crispus L. by testing its in vitro α-glucosidase inhibition and in vivo antihyperglycemic effects on rats with streptozotocin (STZ)-induced diabetes. Better inhibition of α-glucosidase was found with the methanol extract versus the n-hexane and dichloromethane extracts. The methanol extract of the flowers (RCFM) was more effective than that of the leaves (RCHM), with an IC50 of 7.3 ± 0.17 μg/mL for RCFM and 112.0 ± 1.23 μg/mL for RCHM. A bioactive fraction (F89s) also showed good α-glucosidase inhibition (IC50 = 3.8 ± 0.11 μg/mL). In a preliminary study, RCHM and RCFM at 150 mg/kg and F89s at 75 mg/kg after 30 days showed a significant effect on hyperglycemia, reducing glucose levels (82.2, 80.1, and 84.1%, respectively), and improved the lipid, renal, and hepatic profiles of the rats, comparable with the effects of metformin and acarbose. According to the results, the activity of R. crispus L. may be mediated by a diminished rate of disaccharide hydrolysis, associated with the inhibition of α-glucosidase. Thus, R. crispus L. holds promise for the development of auxiliary drugs to treat diabetes mellitus.

Preparation, structural properties, and in vitro and in vivo activities of peptides against dipeptidyl peptidase IV (DPP-IV) and α-glucosidase: a general review

Diabetes is one of the fastest-growing and most widespread diseases worldwide. Approximately 90% of diabetic patients have type 2 diabetes. In 2019, there were about 463 million diabetic patients worldwide. Inhibiting the dipeptidyl peptidase IV (DPP-IV) and α-glucosidase activity is an effective strategy for the treatment of type 2 diabetes. Currently, various anti-diabetic bioactive peptides have been isolated and identified. This review summarizes the preparation methods, structure-effect relationships, molecular binding sites, and effectiveness validation of DPP-IV and α-glucosidase inhibitory peptides in cellular and animal models. The analysis of peptides shows that the DPP-IV inhibitory peptides, containing 2-8 amino acids and having proline, leucine, and valine at their N-terminal and C-terminal, are the highly active peptides. The more active α-glucosidase inhibitory peptides contain 2-9 amino acids and have valine, isoleucine, and proline at the N-terminal and proline, alanine, and serine at the C-terminal.

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.

Design, synthesis, α-glucosidase inhibition, pharmacokinetic, and cytotoxic studies of new indole-carbohydrazide-phenoxy-N-phenylacetamide derivatives

A new series of indole-carbohydrazide-phenoxy-N-phenylacetamide derivatives 7a-l were designed, synthesized, and screened for their α-glucosidase inhibitory abilities and cytotoxic effects. The results obtained in the α-glucosidase inhibition assay indicated that most of the synthesized derivatives displayed good to moderate inhibitory abilities (K_i values ranging from 14.65 ± 2.54 to 37.466 ± 6.46 μM) when compared with the standard drug acarbose (K_i  = 42.38 ± 5.73 μM). Among them, 2-mehoxy-phenoxy derivatives 7l and 7h with 4-nitro and 4-chloro substituents on the phenyl ring of the N-phenylacetamide moiety, respectively, displayed the most inhibition effects. The inhibitory mechanism of these compounds was investigated by molecular docking studies. The in vitro cytotoxicity assay showed that only one compound, 2-methoxy-phenoxy derivative 7k with a 4-bromo substituent on the phenyl ring of the N-phenylacetamide moiety, exhibited moderate cytotoxicity against the human non-small-cell lung cancer cell line A549 and the rest of the compounds show almost no cytotoxicity. Further cytotoxic evaluations were also performed on compound 7k. The in silico pharmacokinetic study predicted that the selected compounds 7l and 7h are likely to be orally active.

Inhibition of α-glucosidase enzyme by 'click'-inspired pharmacophore framework 1,3,4-thiadiazole-1,2,3-triazole hybrids

Aim: α-Glucosidase inhibitors are important oral antidiabetic drugs that are used alone or in combination therapy. Materials & methods: In this regard, 1,3,4-thiadiazoles-1,2,3-triazoles were designed, synthesized and evaluated for α-glucosidase enzyme inhibition. Results: The applied synthesis protocol involved a 'click' reaction between a novel alkyne derived from a 1,3,4-thiadiazole derivative and phenylacetamide azides. The hybrid (9n) bearing 2-methyl and 4-nitro substituents was the best inhibitor with an IC₅₀ value of 31.91 μM (acarbose IC₅₀ = 844.81 μM). The blind molecular docking study of the best derivative (9n) showed that it interacted with the allosteric site's amino acid residues of α-glucosidase. Conclusion: 'Click'-inspired potential α-glucosidase inhibitors (1,3,4-thiadiazole-1,2,3-triazole hybrids) were identified and structure-activity relationship and kinetic and molecular docking studies accomplished.

Structurally diverse glycosides with α-glucosidase inhibitory properties from water extract of the leaves of Cyclocarya paliurus

In this work we investigated the chemical constituents of water extract of the leaves of C. paliurus. Two new megastigmane glycosides (3 and 8), three aliphatic alcohol glycosides (9-11), and two aromatic glycosides (12 and 13), along with fourteen known compounds were isolated, and their in vitro inhibitory activity against α-glucosidase was evaluated. Compounds 13 and 15-18 displayed inhibitory activity with IC₅₀ values varying from 27.05 to 96.58 μM, and the structure-activity relationship among isolated compounds was discussed.

Discovery of New Boswellic Acid Hybrid 1H-1,2,3-Triazoles for Diabetic Management: In Vitro and In Silico Studies

A series of 24 new 1H-1,2,3-triazole hybrids of 3-O-acetyl-11-keto-β-boswellic acid (β-AKBA (1)) and 11-keto-β-boswellic acid (β-KBA (2)) was designed and synthesized by employing "click" chemistry in a highly efficient manner. The 1,3-dipolar cycloaddition reaction between β-AKBA-propargyl ester intermediate 3 or β-KBA-propargyl ester intermediate 4 with substituted aromatic azides 5a-5k in the presence of copper iodide (CuI) and Hünig's base furnished the desired products-1H-1,2,3-triazole hybrids of β-AKBA (6a-6k) and β-KBA (7a-7k)-in high yields. All new synthesized compounds were characterized by ¹H-, ¹³C-NMR spectroscopy, and HR-ESI-MS spectrometry. Furthermore, their α-glucosidase-inhibitory activity was evaluated in vitro. Interestingly, the results obtained from the α-glucosidase-inhibitory assay revealed that all the synthesized derivatives are highly potent inhibitors, with IC₅₀ values ranging from 0.22 to 5.32 µM. Among all the compounds, 6f, 7h, 6j, 6h, 6g, 6c, 6k, 7g, and 7k exhibited exceptional inhibitory potency and were found to be several times more potent than the parent compounds 1 and 2, as well as standard acarbose. Kinetic studies of compounds 6g and 7h exhibited competitive and mixed types of inhibition, with ki values of 0.84 ± 0.007 and 1.18 ± 0.0012 µM, respectively. Molecular docking was carried out to investigate the binding modes of these compounds with α-glucosidase. The molecular docking interactions indicated that that all compounds are well fitted in the active site of α-glucosidase, where His280, Gln279, Asp215, His351, Arg442, and Arg315 mainly stabilize the binding of these compounds. The current study demonstrates the usefulness of incorporating a 1H-1,2,3-triazole moiety into the medicinally fascinating boswellic acids skeleton.

Identification of Phytochemicals in Bioactive Extracts of Acacia saligna Growing in Australia

Acacia saligna growing in Australia has not been fully investigated for its bioactive phytochemicals. Sequential polarity-based extraction was employed to provide four different extracts from individual parts of A. saligna. Bioactive extracts were determined using in vitro antioxidant and yeast α-glucosidase inhibitory assays. Methanolic extracts from barks, leaves, and flowers are the most active and have no toxicity against 3T3-L1 adipocytes. Compound isolation of bioactive extracts provided us with ten compounds. Among them are two novel natural products; naringenin-7-O-α-L-arabinopyranoside 2 and (3S*,5S*)-3-hydroxy-5-(2-aminoethyl) dihydrofuran-2(3H)-one 9. D-(+)-pinitol 5a (from barks and flowers), (-)-pinitol 5b (exclusively from leaf), and 2,4-di-t-butylphenol 7 are known natural products and new to A. saligna. (-)-Epicatechin 6, quercitrin 4, and myricitrin 8 showed potent antioxidant activities consistently in DPPH and ABTS assays. (-)-Epicatechin 6 (IC₅₀ = 63.58 μM),D-(+)-pinitol 5a (IC₅₀ = 74.69 μM), and naringenin 1 (IC₅₀ = 89.71 μM) are the strong inhibitors against the α-glucosidase enzyme. The presence of these compounds supports the activities exerted in our methanolic extracts. The presence of 2,4-di-t-butylphenol 7 may support the reported allelopathic and antifungal activities. The outcome of this study indicates the potential of Australian A. saligna as a rich source of bioactive compounds for drug discovery targeting type 2 diabetes.

Pyrazole scaffold-based derivatives: A glimpse of α-glucosidase inhibitory activity, SAR, and route of synthesis

The α-glucosidase is a validated target to develop drugs for treating type 2 diabetes mellitus. The existing α-glucosidase inhibitors have certain shortcomings related to side effects and route of synthesis. Accordingly, it is inevitable to develop new chemical templates as α-glucosidase inhibitors. Pyrazole derivatives have a special place in medicinal chemistry because of various biological activities. Recently, pyrazole-based heterocyclic compounds have emerged as a promising scaffold to develop α-glucosidase inhibitors. This study focuses on the recently reported pyrazole-based α-glucosidase inhibitors, including their biological activity (in vivo, in vitro, and in silico), structure-activity relationship, and ways of synthesis. The literature revealed the development of several promising pyrazole-based α-glucosidase inhibitors and new synthetic routes for their preparation. The encouraging α-glucosidase inhibitory results of the pyrazole-based heterocyclic compounds make them an attractive target for further research. The authors also foresee the arrival of the pyrazole-based α-glucosidase inhibitors in clinical practice.

An Updated Overview of Synthetic α-glucosidase Inhibitors: Chemistry and Bioactivities

Diabetes mellitus (DM) is a critical global health issue, affecting nearly half a billion people worldwide, with an increasing incidence rate and mortality. Type 2 diabetes is caused by the body's inability to effectively use insulin, and approximately 95% of patients have type 2 diabetes. α-glucosidase has emerged as an important therapeutic target for the treatment of type 2 diabetes. In the past years, three α-glucosidase inhibitors have been approved for clinical use, namely acarbose, voglibose, and miglitol. However, the undesirable effects associated with these carbohydrate mimic-based α-glucosidase inhibitors have limited their clinical applications. Consequently, researchers have shifted their focus towards the development of non-carbohydrate mimic α-glucosidase inhibitors that can safely and effectively manage postprandial hyperglycemia in type 2 diabetes. Herein, this article provides an overview of the synthetic α-glucosidase inhibitors, particularly those based on heterocycles, which have been reported from 2018 to 2022. This article aims to provide useful information for medicinal chemists in further developing clinically available anti-type 2 diabetes drugs.

Choice of Glucose-Lowering Drugs as Initial Monotherapy for Type 2 Diabetes Patients with Contraindications or Intolerance to Metformin: A Systematic Review and Meta-Analysis

BACKGROUND

There are multiple glucose-lowering drugs available as alternative initial monotherapy for type 2 diabetes patients with contraindications or intolerance to metformin. However, little comparative and systematic data are available for them as initial monotherapy. This study estimated and compared the treatment effects of glucose-lowering drugs as initial monotherapy for type 2 diabetes.

METHODS

PubMed, Web of Science, Embase, CNKI, Chongqing VIP, and WanFang Data from 1 January 1990 until 31 December 2020 were searched for randomized controlled trials which compared a glucose-lowering drug with placebo/lifestyle-intervention for type 2 diabetes. Drug classes included metformin, sulfonylureas (SUs), thiazolidinediones (TZDs), glinides (NIDEs), α-glucosidase inhibitors (AGIs), dipeptidyl peptidase-4 inhibitors (DPP-4is), sodium-glucose cotransporter-2 inhibitors (SGLT2is), insulins (INSs), and glucagon-like peptide-1 receptor agonists (GLP-1RAs).

RESULTS

A total of 185 trials were included, identifying 38,376 patients from 56 countries across six continents. When choosing an initial drug monotherapy alternative to metformin, SUs were most efficacious in reducing HbA1c (-1.39%; 95% CI -1.63, -1.16) and FPG (-2.70 mmol/L; 95% CI -3.18, -2.23), but increased hypoglycemia risks (5.44; 95% CI 2.11, 14.02). GLP-1RAs were most efficacious in reducing BMI (-1.05 kg/m²; 95% CI -1.81, -0.29) and TC (-0.42 mmol/L; 95% CI -0.61, -0.22). TZDs were most efficacious in increasing HDL-C (0.12 mmol/L; 95% CI 0.07, 0.17). SGLT2is were most efficacious in lowering SBP (-4.18 mmHg; 95% CI -4.84, -3.53). While AGIs conferred higher risk of AE-induced discontinuations (2.57; 95% CI 1.64, 4.03). Overall, only GLP-1RAs showed an integrated beneficial effect on all outcomes. Our results also confirmed the intraclass differences in treatment effects across drugs. Most trials were short-term, and no significant differences in mortality, total vascular events, myocardial infarction, heart failure, stroke, or diabetic nephropathy were observed across drug classes.

CONCLUSIONS

Our results suggest a potential treatment hierarchy for decision-makers, with GLP-1RAs being the preferred alternative therapy to metformin regarding their favorable efficacy and safety profiles.

Rapid Screening of Nonalkaloid α-Glucosidase Inhibitors from a Mulberry Twig Extract Using Enzyme-Functionalized Magnetic Nanoparticles Coupled with UPLC-MS/MS

Mulberry twigs are an important source of α-glucosidase inhibitors. To date, research studies on α-glucosidase in mulberry twigs have mainly focused on alkaloids such as 1-deoxynojirimycin (DNJ). Preliminary studies have shown that there may be more active nonalkaloid α-glucosidase inhibitors in mulberry twigs. In this study, we immobilized α-glucosidase on Fe₃O₄@SiO₂ for the first time and rapidly screened four nonalkaloid α-glucosidase inhibitors (kuwanon G, kuwanon C, kuwanon H, and morusin) using ligand fishing technology with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) from the mulberry twig extract of Jialing 20, the excellent artificial triploid variety of mulberry cultivated extensively in Southwest China. The half maximal inhibitory concentrations (IC₅₀) of kuwanon H and kuwanon G were 2.82 ± 0.68 and 2.83 ± 0.31 μM, respectively, with better inhibition activity than that of DNJ (with an IC₅₀ of 7.04 ± 0.82 μM). Meanwhile, the molecular docking results showed that the action sites of these two isopentenyl flavonoids on α-glucosidase were different from that of DNJ. In brief, this work is beneficial to discovering new α-glucosidase inhibitors from mulberry twigs quickly and accurately and provides a theoretical basis for the mulberry twig extract as a functional food or a natural hypoglycemic drug source, as well as a reference for directional breeding of mulberry, which greatly improves the exploitation and utilization value of mulberry twigs as an agricultural byproduct in the fields of agricultural production, functional food, and natural medicine.

α-Glucosidase inhibitory effect of an anthraquinonoid produced by Fusarium incarnatum GDZZ-G2

α-Glucosidase is the key enzyme on carbohydrate metabolism, and its bioactive inhibitors are supposed to be an effective therapeutic for type 2 diabetes mellitus. During our continuing study for discovering α-glucosidase inhibitors, a fungus GDZZ-G2 which is derived from a medicinal plant Callicarpa kwangtungensis Chun, exhibited significant inhibition on α-glucosidase. The strain was identified as Fusarium incarnatum by morphological and molecular methods. Further bioassay-guided fractionation result in six known secondary metabolites (1-6). All the compounds except 4 were isolated from F. incarnatum for the first time. Among them, an anthraquinonoid (S)-1,3,6-trihydroxy-7-(1-hydroxyethyl)anthracene-9,10-dione (compound 1) exhibited strong inhibitory effect against α-glucosidase (IC₅₀  = 77.67 ± 0.67 μΜ), compared with acarbose (IC₅₀  = 711.8 ± 5 μΜ). An enzyme kinetics analysis revealed that compound 1 was an uncompetitive inhibitor. Besides, docking simulations predicted that compound 1 inhibited α-glucosidase substrate complex by binding Gln322, Gly306, Thr307, and Ser329 through hydrogen-bond interactions. Our findings suggested that compound 1 can be considered a lead compound for further modifications and the development of a new effective drug candidate in the treatment of type 2 diabetes mellitus.

leaf-tea and in silico analysis

Cerasus humilis(Bge.) Sok. leaf-tea (CLT) has a potential anti-α-glucosidase effect. However, its anti-α-glucosidase functional compositions remain unclear. Results showed that 70% methanol extract of CLT (IC₅₀ = 36.57 μg/mL) with the highest total phenolic/flavonoid contents exhibited significantly higher α-glucosidase inhibitory activity (α-GIA) than acarbose (IC₅₀ = 189.57 μg/mL). Additionally, phenolic constituents of the CLT extract were analyzed for the first time in this work. Ten major potential α-glucosidase inhibitors (α-GIs) with high bio-affinity degree in the CLT extract were recognized using a bio-affinity ultra-filtration and HPLC-ESI-qTOF-MS/MS method. In vitro α-GIA assay confirmed that myricetin (IC₅₀ = 36.17 μg/mL), avicularin (IC₅₀ = 69.84 μg/mL), quercitrin, isoquercitrin, prunin and guajavarin were responsible for the α-GIA of the CLT extract. More importantly, the interaction mechanism between α-GIs and α-glucosidase was investigated via in silico analysis. This study provides a high-throughput screening platform for identification of the potential α-GIs from natural products.

Anti-α-Glucosidase and Antiglycation Activities of α-Mangostin and New Xanthenone Derivatives: Enzymatic Kinetics and Mechanistic Insights through In Vitro Studies

Diabetes mellitus is characterized by chronic hyperglycemia that promotes ROS formation, causing severe oxidative stress. Furthermore, prolonged hyperglycemia leads to glycation reactions with formation of AGEs that contribute to a chronic inflammatory state. This research aims to evaluate the inhibitory activity of α-mangostin and four synthetic xanthenone derivatives against glycation and oxidative processes and on α-glucosidase, an intestinal hydrolase that catalyzes the cleavage of oligosaccharides into glucose molecules, promoting the postprandial glycemic peak. Antiglycation activity was evaluated using the BSA assay, while antioxidant capacity was detected with the ORAC assay. The inhibition of α-glucosidase activity was studied with multispectroscopic methods along with inhibitory kinetic analysis. α-Mangostin and synthetic compounds at 25 µM reduced the production of AGEs, whereas the α-glucosidase activity was inhibited only by the natural compound. α-Mangostin decreased enzymatic activity in a concentration-dependent manner in the micromolar range by a reversible mixed-type antagonism. Circular dichroism revealed a rearrangement of the secondary structure of α-glucosidase with an increase in the contents of α-helix and random coils and a decrease in β-sheet and β-turn components. The data highlighted the anti-α-glucosidase activity of α-mangostin together with its protective effects on protein glycation and oxidation damage.

Synthesis and biological evaluation of (20S,24R)-epoxy-dammarane-3β,12β,25-triol derivatives as α-glucosidase and PTP1B inhibitors

The dammarane triterpenoid (20S,24R)-epoxy-dammarane-3β,12β,25-triol obtained from Cyclocarya paliurus in our previous study showed inhibitory activity on α-glucosidase in vitro with an inhibitory ratio of 32.2% at the concentration of 200 μM. In order to reveal the structure-activity relationships (SARs) and get more active compounds, 42 derivatives of (20S,24R)-epoxy-dammarane-3β,12β,25-triol were synthesized by chemical modification on the hydroxyls (C-3 and C-12), rings A and E, and assayed for their α-glucosidase and PTP1B inhibitory activities. Two compounds (8, 26) increased activity against α-glucosidase, and four compounds (8, 15, 26, 42) significantly inhibited PTP1B. It was noted that compounds 8 and 26 could inhibit both α-glucosidase and PTP1B as dual-target inhibitors with IC₅₀ values of 489.8, 467.7 μM (α-glucosidase) and 319.7, 269.1 μM (PTP1B). Compound 26 was revealed to be a mix-type inhibitor on α-glucosidase and a noncompetitive-type inhibitor on PTP1B based on enzyme kinetic study. Furthermore, compound 42 could selectively inhibited PTP1B as a mix-type inhibitor with IC₅₀ value of 134.9 μM, which was 2.5-fold higher than the positive control, suramin sodium (IC₅₀ 339.0 μM), but not inhibit α-glucosidase.

-Glucosidase inhibitors screening from Cyclocarya paliurus based on spectrum-effect relationship and UPLC-MS/MS

Cyclocarya paliurus is an edible and medicinal plant exhibiting significant hypoglycemic effect. However, its active components are still unclear and need further elucidation. In this research, the active components of the leaves of C. paliurus responsible for α-glucosidase inhibitory activity were screened and identified based on spectrum-effect relationship study in combination with ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) analysis. The 70% ethanol eluate fraction of the leaves of C. paliurus with the strongest α-glucosidase inhibitory activity was obtained after extraction and purification with macroporous resin. Their chromatographic fingerprints (15 batches) were established by UPLC analysis and 32 common peaks were specified by similarity analysis. Their IC₅₀ values for α-glucosidase inhibition were measured by an enzymatic reaction. Several multivariate statistical analysis methods including hierarchical cluster analysis, principal component analysis, partial least square analysis and grey relational analysis were applied to explore the spectrum-effect relationship between common peaks and IC₅₀ values, and the chromatographic peaks making great contribution to efficacy were screened out. To further elucidate the active components of leaves of C. paliurus, the 70% ethanol eluate fraction was characterized by UPLC-MS/MS analysis, and 10 compounds were identified. This study provided a valuable reference for further research and development of hypoglycemic active components of C. paliurus.

Phytochemical Screening and Antioxidant Activity of Seven Native Species Growing in the Forests of Southern Chilean Patagonia

The genus Nothofagus is one of the most abundant in the subantarctic Patagonian forests. Five species inhabit these ecosystems, three evergreen (Nothofagus betuloides, Nothofagus dombeyi, and Nothofagus nitida) and two deciduous (Nothofagus pumilio and Nothofagus antarctica). This is the first report on the levels of secondary metabolites and the antioxidant capacity of Patagonian tree species growing in natural environments. The aim of this work was to carry out a phytochemical screening, to determine the antioxidant capacity, the sun protection factor, and the α-glucosidase and tyrosinase inhibitory activity of foliar extracts of the five previous species. Besides, Aristotelia chilensis and Berberis microphylla, two species of Patagonian shrubs growing in the same forests, were used as reference. N. dombeyi was the Nothofagus with the best antioxidant capacity. B. microphylla differed from all studied species. Moreover, the Nothofagus was split into two groups. N. betuloides and N. dombeyi are the most similar species to A. chilensis. The α-glucosidase was completely inhibited by all studied extracts. Furthermore, N. antarctica, N.pumilio, and N. nitida inhibited about 70% of the tyrosinase activity. All the results found in this study for the species of the genus Nothofagus support further research on their potential beneficial properties for human health.

by surface plasmon resonance coupled with ultra-performance liquid chromatography and quadrupole-time-of-flight-mass spectrometry

Extracts from the bran of Chenopodium quinoa Willd. (QBE) were reported to be active in inhibiting α-glycosidase, a promising target for treatment of diabetes mellitus. However, the constituents responsible for the α-glucosidase-inhibiting activity of QBE have not been fully characterized. The present study aimed to set up a method for rapid identification of glycosidase inhibiting compounds from the quinoa bran. With surface plasmon resonance (SPR) coupled with liquid chromatography-mass spectrometry (LC-MS), we identified eight flavonoids and ten triterpenoid saponins that may bind to the α-glycosidase. Analysis of the interaction kinetics by molecular docking supported their α-glucosidase-inhibiting activity and revealed the potential mechanisms for the inhibitory effects. In summary, this study established a SPR and LC-MS-based method for rapid in vitro screening of α-glucosidase inhibitors and suggested the quinoa bran a potential natural source of α-glucosidase inhibitors.

Characteristics of Food Protein-Derived Antidiabetic Bioactive Peptides: A Literature Update

Diabetes, a glucose metabolic disorder, is considered one of the biggest challenges associated with a complex complication of health crises in the modern lifestyle. Inhibition or reduction of the dipeptidyl peptidase IV (DPP-IV), alpha-glucosidase, and protein-tyrosine phosphatase 1B (PTP-1B) enzyme activities or expressions are notably considered as the promising therapeutic strategies for the management of type 2 diabetes (T2D). Various food protein-derived antidiabetic bioactive peptides have been isolated and verified. This review provides an overview of the DPP-IV, PTP-1B, and α-glucosidase inhibitors, and updates on the methods for the discovery of DPP-IV inhibitory peptides released from food-protein hydrolysate. The finding of novel bioactive peptides involves studies about the strategy of separation fractionation, the identification of peptide sequences, and the evaluation of peptide characteristics in vitro, in silico, in situ, and in vivo. The potential of bioactive peptides suggests useful applications in the prevention and management of diabetes. Furthermore, evidence of clinical studies is necessary for the validation of these peptides’ efficiencies before commercial applications.

Medicinal chemistry of anthranilic acid derivatives: A mini review

Anthranilic acid and its analogues present a privileged profile as pharmacophores for the rational development of pharmaceuticals deliberated for managing the pathophysiology and pathogenesis of various diseases. The substitution on anthranilic acid scaffold provides large compound libraries, which enable a comprehensive assessment of the structure activity relationship (SAR) analysis for the identification of hits and leads in a typical drug development paradigm. Besides, their widespread applications as anti-inflammatory fenamates, the amide and anilide derivatives of anthranilic acid analogues play a central role in the management of several metabolic disorders. In addition, these derivatives of anthranilic acid exhibit interesting antimicrobial, antiviral and insecticidal properties, whereas the derivatives based on anthranilic diamide scaffold present applications as P-glycoprotein inhibitors for managing the drug resistance in cancer cells. In addition, the anthranilic acid derivatives serve as the inducers of apoptosis, inhibitors of hedgehog signaling pathway, inhibitors of mitogen activated protein kinase pathway, and the inhibitors of aldo-keto reductase enzymes. The antiviral derivatives of anthranilic acid focus on the inhibition of hepatitis C virus NS5B polymerase to manifest considerable antiviral properties. The anthranilic acid derivatives reportedly present neuroprotective applications by downregulating the key pathways responsible for the manifestation of neuropathological features and neurodegeneration. Nevertheless, the transition metal complexes of anthranilic acid derivatives offer therapeutic applications in diabetes mellitus, and obesity by regulating the activity of α-glucosidase. The present review demonstrates a critical analysis of the therapeutic profile of the key derivatives of anthranilic acid and its analogues for the rational development of pharmaceuticals and therapeutic molecules.

Reusable Fluorescent Nanobiosensor Integrated in a Multiwell Plate for Screening and Quantification of Antidiabetic Drugs

A highly stable and reusable fluorescent multisample nanobiosensor for the detection of α-glucosidase inhibitors has been developed by coupling fluorescent liposomal nanoparticles based on conjugated polymers (L-CPNs) to the enzyme α-glucosidase, one of the main target enzymes in the treatment of type 2 diabetes. The mechanism of sensing is based on the fluorescence "turn-on" of L-CPNs by p-nitrophenol (PNP), the end product of the enzymatic hydrolysis of p-nitrophenyl-α-d-glucopyranoside. L-CPNs, composed of lipid vesicles coated with a blue-emitting cationic polyfluorene, were designed and characterized to obtain a good response to PNP. Two nanobiosensor configurations were developed in this study. In the first step, a single-sample nanobiosensor composed of L-CPNs and α-glucosidase entrapped in a sol-gel glass was developed in order to characterize and optimize the device. In the second part, the nanobiosensor was integrated and adapted to a multiwell microplate and the possibility of reusing it and performing multiple measurements simultaneously with samples containing different α-glucosidase inhibitors was investigated. Using super-resolution confocal microscopy, L-CPNs could be visualized within the sol-gel matrix, and the quenching of their fluorescence, induced by the substrate, was directly observed in situ. The device was also shown to be useful not only as a platform for screening of antidiabetic drugs but also for quantifying their presence. The latter application was successfully tested with the currently available drug, acarbose.

Diarylheptanoid-chalcone hybrids with PTP1B and α-glucosidase dual inhibition from Alpinia katsumadai

The EtOH extracts of the dried seeds of Alpinia katsumadai were revealed with hypoglycemic effects on db/db mice at the concentration of 200 mg/kg. In order to clarify the antidiabetic constituents, 16 new diarylheptanoid-chalcone hybrids, katsumadainols A₁-A₁₆ (1-16), together with 13 known analogues (17-29), were isolated from A. katsumadai under the guidance of bioassay. Most of the compounds showed α-glucosidase and PTP1B dual inhibition, among which compounds 1-3, 5-7, 11-14, 21-25, and 27 showed PTP1B/TCPTP selective inhibition with IC₅₀ values ranging from 22.0 to 96.7 μM, which were 2-10 times more active than sodium orthovanadate (IC₅₀, 215.7 μM). All compounds exhibited obvious inhibition against α-glucosidase with IC₅₀ values of 2.9-29.5 μM, indicating 6-59 times more active than acarbose (IC₅₀, 170.9 μM). Study of enzyme kinetics indicated compounds 1, 3, and 12 were PTP1B and α-glucosidase mixed-type inhibitors with K_i values of 13.1, 12.9, 21.6 μM, and 4.9, 7.4, 3.4 μM, respectively.

Characterization of α-Glucosidase Inhibitors from Psychotria malayana Jack Leaves Extract Using LC-MS-Based Multivariate Data Analysis and In-Silico Molecular Docking

Psychotria malayana Jack has traditionally been used to treat diabetes. Despite its potential, the scientific proof in relation to this plant is still lacking. Thus, the present study aimed to investigate the α-glucosidase inhibitors in P.malayana leaf extracts using a metabolomics approach and to elucidate the ligand–protein interactions through in silico techniques. The plant leaves were extracted with methanol and water at five various ratios (100, 75, 50, 25 and 0% v/v; water–methanol). Each extract was tested for α-glucosidase inhibition, followed by analysis using liquid chromatography tandem to mass spectrometry. The data were further subjected to multivariate data analysis by means of an orthogonal partial least square in order to correlate the chemical profile and the bioactivity. The loading plots revealed that the m/z signals correspond to the activity of α-glucosidase inhibitors, which led to the identification of three putative bioactive compounds, namely 5′-hydroxymethyl-1′-(1, 2, 3, 9-tetrahydro-pyrrolo (2, 1-b) quinazolin-1-yl)-heptan-1′-one (1), α-terpinyl-β-glucoside (2), and machaeridiol-A (3). Molecular docking of the identified inhibitors was performed using Auto Dock Vina software against the crystal structure of Saccharomyces cerevisiae isomaltase (Protein Data Bank code: 3A4A). Four hydrogen bonds were detected in the docked complex, involving several residues, namely ASP352, ARG213, ARG442, GLU277, GLN279, HIE280, and GLU411. Compound 1, 2, and 3 showed binding affinity values of −8.3, −7.6, and −10.0 kcal/mol, respectively, which indicate the good binding ability of the compounds towards the enzyme when compared to that of quercetin, a known α-glucosidase inhibitor. The three identified compounds that showed potential binding affinity towards the enzymatic protein in molecular docking interactions could be the bioactive compounds associated with the traditional use of this plant.

An overview on the role of bioactive α-glucosidase inhibitors in ameliorating diabetic complications

Recently the use of bioactive α-glucosidase inhibitors for the treatment of diabetes have been proven to be the most efficient remedy for controlling postprandial hyperglycemia and its detrimental physiological complications, especially in type 2 diabetes. The carbohydrate hydrolysing enzyme, α-glucosidase, is generally competitively inhibited by the α-glucosidase inhibitors and results in the delayed glucose absorption in small intestine, ultimately controlling the postprandial hyperglycemia. Here we have reviewed the most recent updates in the bioactive α-glucosidase inhibitors category. This review provides an overview of the α-glucosidase inhibitory potentials and efficiency of controlling postprandial hyperglycemia of various bioactive compounds such as flavonoids, phenolic compound, polysaccharide, betulinic acid, tannins, anthocyanins, steroids, polyol, polyphenols, galangin, procyanidins, hydroxyl-α-sanshool, hydroxyl-β-sanshool, erythritol, ganomycin, caffeoylquinic acid, resin glycosides, saponins, avicularin, oleanolic acids, urasolic acid, ethanolic extracts etc., from various dietary and non-dietary naturally occurring sources.

Nineteen New Flavanol-Fatty Alcohol Hybrids with α-Glucosidase and PTP1B Dual Inhibition: One Unusual Type of Antidiabetic Constituent from Amomum tsao-ko

The dried fruits of Amomum tsao-ko were first revealed to have hypoglycemic effects on db/db mice at a concentration of 200 mg/kg. In order to clarify the antidiabetic constituents, 19 new flavanol-fatty alcohol hybrids, tsaokoflavanols A-S (1-19), were isolated and determined by extensive spectroscopic data and ECD calculations. Most of the compounds showed α-glucosidase and PTP1B dual inhibition, among which 1, 2, 6, 11, and 18 exhibited obvious activity against α-glucosidase with IC₅₀ values of 5.2-9.0 μM, 20-35 times stronger than that of acarbose (IC₅₀, 180.0 μM); meanwhile, 6, 10-12, and 19 were PTP1B/TCPTP-selective inhibitors with IC₅₀ values of 56.4-80.4 μM, 2-4 times stronger than that of suramin sodium (IC₅₀, 200.5 μM). Enzyme kinetics study indicated that compounds 1, 2, 6, and 11 were α-glucosidase and PTP1B mixed-type inhibitors with K_i values of 13.0, 11.7, 2.9, and 5.3 μM and 142.3, 88.9, 39.2, and 40.8 μM, respectively. Docking simulations proved the importance of hemiacetal hydroxy, the orientation of 3,4-dihydroxyphenyl, and the length of alkyl in binding with α-glucosidase and PTP1B.

and Identification of Phytochemical Profiling by HPLC-QTOF-MS/MS

Ceratophyllum demersum L. (CDL) is a traditional Chinese herb to treat many diseases, but research on its anti-diabetic activity is not available. In this research, the α-glucosidase inhibitory ability and phytochemical constituents of CDL extract were firstly studied. Optimal ultrasound-assisted extraction conditions for α-glucosidase inhibitors (AGIs) were optimized by single factor experiment and response surface methodology (RSM), which was confirmed as 70% methanol, liquid-to-solid ratio of 43 (mL/g), extraction time of 54 min, ultrasonic power of 350 W, and extraction temperature of 40 °C. The lowest IC₅₀ value for α-glucosidase inhibition was 0.15 mg dried material/mL (mg DM/mL), which was much lower than that of acarbose (IC₅₀ value of 0.64 mg DM/mL). In total, 80 compounds including 8 organic acids, 11 phenolic acids, 25 flavonoids, 21 fatty acids, and 15 others were identified or tentatively identified from CDL extract by HPLC-QTOF-MS/MS analysis. The results suggested that CDL could be a potential source of α-glucosidase inhibitors. It can also provide useful phytochemical information for research into other bioactivities.

Triterpenic Acids as Non-Competitive α-Glucosidase Inhibitors from Boswellia elongata with Structure-Activity Relationship: In Vitro and In Silico Studies

Fourteen triterpene acids, viz., three tirucallane-type (1-3), eight ursane-type (4-11), two oleanane-type (12, 13) and one lupane type (21), along with boswellic aldehyde (14), α-amyrine (15), epi-amyrine (16), straight chain acid (17), sesquiterpene (19) and two cembrane-type diterpenes (18, 20) were isolated, first time, from the methanol extract of Boswellia elongata resin. Compound (1) was isolated for first time as a natural product, while the remaining compounds (2‒21) were reported for first time from B. elongata. The structures of all compounds were confirmed by advanced spectroscopic techniques including mass spectrometry and also by comparison with the reported literature. Eight compounds (1-5, 11, 19 and 20) were further screened for in vitro α-glucosidase inhibitory activity. Compounds 3-5 and 11 showed significant activity against α-glucosidase with IC₅₀ values ranging from 9.9-56.8 μM. Compound 4 (IC₅₀ = 9.9 ± 0.48 μM) demonstrated higher inhibition followed by 11 (IC₅₀ = 14.9 ± 1.31 μM), 5 (IC₅₀ = 20.9 ± 0.05 μM) and 3 (IC₅₀ = 56.8 ± 1.30 μM), indicating that carboxylic acid play a key role in α-glucosidase inhibition. Kinetics studies on the active compounds 3-5 and 11 were carried out to investigate their mechanism (mode of inhibition and dissociation constants K_i). All compounds were found to be non-competitive inhibitors with K_i values in the range of 7.05 ± 0.17-51.15 ± 0.25 µM. Moreover, in silico docking was performed to search the allosteric hotspot for ligand binding which is targeted by our active compounds investigates the binding mode of active compounds and it was identified that compounds preferentially bind in the allosteric binding sites of α-glucosidase. The results obtained from docking study suggested that the carboxylic group is responsible for their biologic activities. Furthermore, the α-glucosidase inhibitory potential of the active compounds is reported here for the first time.

Inhibitory effect of Artocarpus lakoocha Roxb and oxyresveratrol on α-glucosidase and sugar digestion in Caco-2 cells

Long-term diabetic complications are exacerbated by post-prandial hyperglycemia which could be ameliorated by α-glucosidase inhibitor including oxyresveratrol. Puag-Haad is an aqueous extract from Artocarpus lakoocha Roxb. containing ~65% oxyresveratrol. Oxyresveratrol is an inhibitor of isolated yeast α-glucosidase enzyme but has not been tested on intact gut enterocytes where the enzyme is membrane-bound. Accordingly, differentiated Caco-2 cells that contain the native enzyme were used to test maltose hydrolysis in the present study. The results demonstrated that purified yeast α-glucosidase was non-competitively inhibited by oxyresveratrol (Ki 54.4 ± 0.7 μg/mL) and Puag-Haad (2.7 ± 0.1 μg/mL) compared to 153.8 ± 4.3 μg/mL acarbose, an anti-diabetic drug. In differentiated Caco-2 cells, both oxyresveratrol and Puag-Haad inhibited maltose hydrolysis with lesser potency compared to acarbose. Thus, although weaker than acarbose, oxyresveratrol and Puag-Haad do not inhibit pancreatic amylase which might be a therapeutic asset in preventing fermentation of unabsorbed carbohydrate causes abdominal bloating, flatulence, or diarrhea. Oxyresveratrol and Puag-Haad may help control postprandial hyperglycemia with low risk of gastrointestinal side effects.

Separation of α-glucosidase inhibitors from Potentilla kleiniana Wight et Arn using solvent and flow-rate gradient high-speed counter-current chromatography target-guided by ultrafiltration HPLC-MS screening

INTRODUCTION

Potentilla kleiniana Wight et Arn is widely used as a herbal medicine to treat type 2 diabetes. However, detailed information about its active compounds is lacking.

OBJECTIVE

To develop an efficient method for the rapid screening and separation of α-glucosidase inhibitors from Potentilla kleiniana Wight et Arn.

METHODOLOGY

Potential α-glucosidase inhibitors from Potentilla kleiniana Wight et Arn were rapidly screened out through ultrafiltration high-performance liquid chromatography mass spectrometry (HPLC-MS), and then followed by a target-guided high-speed counter-current chromatography (HSCCC) separation using two-phase solvent systems composed of n-hexane/ethyl acetate/methanol/water (1:10:1:10, v/v/v/v and 1:10:5:6, v/v/v/v), and adopting increasing flow-rate from 1.5 to 3.0 mL/min after 200 min. Their structures were identified by ultraviolet (UV), MS, proton nuclear magnetic resonance (¹ H-NMR) and carbon-13 (¹³ C)-NMR, and their α-glucosidase inhibitory activities were assessed by in vitro assay.

RESULTS

Five α-glucosidase inhibitors including gallic acid (25.7 mg, 98.2%, 1), brevifolincarboxylic acid (9.86 mg, 95.3%, 2), ethyl evifolincarboxylate (13.26 mg, 97.6%, 3), 3,3'-di-O-methylellagic acid-4'-O-β-d-glucopyranoside (16.26 mg, 95.1%, 4), and 3,3'-di-O-methylellagic acid (10.54 mg, 96.8%, 5) were successfully purified from 250 mg n-butanol extract in a single run. Compounds 1, 2, 4 and 5 exhibited stronger α-glucosidase inhibitory activities[half maximal inhibition concentration (IC₅₀ ) values at 173.41 ± 6.35, 323.46 ± 8.08, 44.63 ± 2.50, and 20.73 ± 2.56 μM, respectively] than acarbose (IC₅₀ value at 332.12 ± 5.52 μM, reference compound).

CONCLUSIONS

Notably, compounds 2-5 were reported in the Potentilla kleiniana Wight et Arn for the first time. The results indicated that the proposed method could be applied for the rapid screening and preparative separation of α-glucosidase inhibitors from a complex matrix.

Maltase Decorated by Chiral Carbon Dots with Inhibited Enzyme Activity for Glucose Level Control

Carbon dots (CDs) have attracted increasing attention in disease therapy owing to their low toxicity and good biocompatibility. Their therapeutic effect strongly depends on the CDs structure (e.g., size or functional groups). However, the impact of CDs chirality on maltase and blood glucose level has not yet been fully emphasized and studied. Moreover, in previous reports, chiral CDs with targeted optical activity have to be synthesized from precursors of corresponding optical rotation, severely limiting chiral CDs design. Here, chiral CDs with optical rotation opposite to that of the precursor are facilely prepared through electrochemical polymerization. Interestingly, their chirality can be regulated by simply adjusting reaction time. At last, the resultant (+)-DCDs (700 µg mL^-1 ) are employed to modify maltase in an effort to regulate the hydrolytic rate of maltose, showing an excellent inhibition ratio to maltase of 54.7%, significantly higher than that of (-)-LCDs (15.5%) in the same reaction conditions. The superior performance may be attributed to the preferable combination of DCDs with maltase. This study provides an electrochemical method to facilely regulate CDs chirality, and explore new applications of chiral CDs as antihyperglycemic therapy for controlling blood glucose levels.

Formulation of a Mixture of Plant Extracts for Attenuating Postprandial Glycemia and Diet-Induced Disorders in Rats

The aim of this study was to design a mixture consisting of plant-derived preparations containing inhibitors of carbohydrate digestion and/or glucose absorption that could lower postprandial glycemia and attenuate dietary-induced disorders. The following standardized preparations were tested: white mulberry leaf extract, green coffee bean extract, white kidney bean extract, pomelo fruit extract, bitter melon fruit extract, and purified l-arabinose. The study design was composed of oral sucrose and starch tolerance tests in Wistar rats preceded by a single ingestion of the preparations or their mixtures. Then, a 20 week-long experiment was conducted on rats that were fed a high-fat diet and supplemented with the most effective mixture. Based on the results of the oral sucrose and starch tolerance tests, the mulberry leaf extract, l-arabinose, kidney bean extract, and coffee bean extract were selected for composing three mixtures. The most effective inhibition of postprandial glycemia in the oral tolerance tests was observed after the ingestion of a mixture of mulberry leaf, kidney bean, and coffee bean extract. The glucose-lowering effect of the mixture and its effective dosage was confirmed in the feeding experiment.

Head-to-Head Comparison of the Hypoglycemic Efficacy and Safety Between Dipeptidyl Peptidase-4 Inhibitors and α-Glucosidase Inhibitors in Patients With Type 2 Diabetes Mellitus: A Meta-Analysis of Randomized Controlled Trials

Background: The α-glucosidase inhibitors (AGIs) are commonly prescribed in Asian patients with type 2 diabetes mellitus (T2DM), but with a high incidence of gastrointestinal side effects. This study was aimed to compare the efficacy and safety of dipeptidyl peptidase-4 (DPP4) inhibitors and AGIs in T2DM patients in a meta-analysis.

Methods: Randomized controlled trials were identified via systematic search of PubMed, Embase, and Cochrane’s Library databases from inception to February, 2019. Meta-analyses were performed via a random or a fixed effect model according to the heterogeneity.

Results: Eighteen studies with a total of 4,051 patients with T2DM were included. The DPP4 inhibitors were associated with lower reduction of glycosylated hemoglobin (HbA1c) as compared with AGIs [weighed mean difference (WMD): −0.37%, p < 0.001]. Subgroup analyses indicated that the benefit of DPP4 inhibitors as compared with AGIs on HbA1c were independent of study design, scale, baseline HbA1c, with or without concurrent medications, or follow-up durations. Moreover, compared to AGIs, DPP4 inhibitors was associated with lower reductions of fasting blood glucose (WMD: −0.53 mmol/L, P < 0.001) and postprandial glucose at 2h (WMD: −0.60 mmol/L, P = 0.04), moderately increased body weight (WMD: 0.34 kg, P = 0.02), and decreased risk of gastrointestinal adverse events [risk ratio (RR): 0.48, P < 0.001], but unaffected risk of symptomatic hypoglycemia (RR: 0.96, P = 0.90).

Conclusions: The DPP4 inhibitors are superior to AGIs in T2DM patients for better glycemic control and lower risks of gastrointestinal side effects.

Investigation on the Enzymatic Profile of Mulberry Alkaloids by Enzymatic Study and Molecular Docking

α-glucosidase inhibitors (AGIs) have been an important category of oral antidiabetic drugs being widely exploited for the effective management of type 2 diabetes mellitus. However, the marketed AGIs not only inhibited the disaccharidases, but also exhibited an excessive inhibitory effect on α-amylase, resulting in undesirable gastrointestinal side effects. Compared to these agents, Ramulus Mori alkaloids (SZ-A), was a group of effective alkaloids from natural Morus alba L., and showed excellent hypoglycemic effect and fewer side effects in the Phase II/III clinical trials. Thus, this paper aims to investigate the selective inhibitory effect and mechanism of SZ-A and its major active ingredients (1-DNJ, FA and DAB) on different α-glucosidases (α-amylase and disaccharidases) by using a combination of kinetic analysis and molecular docking approaches. From the results, SZ-A displayed a strong inhibitory effect on maltase and sucrase with an IC₅₀ of 0.06 μg/mL and 0.03 μg/mL, respectively, which was similar to the positive control of acarbose with an IC₅₀ of 0.07 μg/mL and 0.68 μg/mL. With regard to α-amylase, SZ-A exhibited no inhibitory activity at 100 μg/mL, while acarbose showed an obvious inhibitory effect with an IC₅₀ of 1.74 μg/mL. The above analysis demonstrated that SZ-A could selectively inhibit disaccharidase to reduce hyperglycemia with a reversible competitive inhibition, which was primarily attributed to the three major active ingredients of SZ-A, especially 1-DNJ molecule. In the light of these findings, molecular docking study was utilized to analyze their inhibition mechanisms at molecular level. It pointed out that acarbose with a four-ring structure could perform desirable interactions with various α-glucosidases, while the three active ingredients of SZ-A, belonging to monocyclic compounds, had a high affinity to the active site of disaccharidases through forming a wide range of hydrogen bonds, whose affinity and consensus score with α-amylase was significantly lower than that of acarbose. Our study illustrates the selective inhibition mechanism of SZ-A on α-glucosidase for the first time, which is of great importance for the treatment of type 2 diabetes mellitus.

Dual targeting of PTP1B and glucosidases with new bifunctional iminosugar inhibitors to address type 2 diabetes

The diffusion of type 2 diabetes (T2D) throughout the world represents one of the most important health problems of this century. Patients suffering from this disease can currently be treated with numerous oral anti-hyperglycaemic drugs, but none is capable of reproducing the physiological action of insulin and, in several cases, they induce severe side effects. Developing new anti-diabetic drugs remains one of the most urgent challenges of the pharmaceutical industry. Multi-target drugs could offer new therapeutic opportunities for the treatment of T2D, and the reported data on type 2 diabetic mice models indicate that these drugs could be more effective and have fewer side effects than mono-target drugs. α-Glucosidases and Protein Tyrosine Phosphatase 1B (PTP1B) are considered important targets for the treatment of T2D: the first digest oligo- and disaccharides in the gut, while the latter regulates the insulin-signaling pathway. With the aim of generating new drugs able to target both enzymes, we synthesized a series of bifunctional compounds bearing both a nitro aromatic group and an iminosugar moiety. The results of tests carried out both in vitro and in a cell-based model, show that these bifunctional compounds maintain activity on both target enzymes and, more importantly, show a good insulin-mimetic activity, increasing phosphorylation levels of Akt in the absence of insulin stimulation. These compounds could be used to develop a new generation of anti-hyperglycemic drugs useful for the treatment of patients affected by T2D.

Crosstalk between gut microbiota and antidiabetic drug action

Type 2 diabetes (T2D) is a disorder characterized by chronic inflated blood glucose levels (hyperglycemia), at first due to insulin resistance and unregulated insulin secretion but with tendency towards global spreading. The gut microbiota is recognized to have an influence on T2D, although surveys have not formed a clear overview to date. Because of the interactions between gut microbiota and host homeostasis, intestinal bacteria are believed to play a large role in various diseases, including metabolic syndrome, obesity and associated disease. In this review, we highlight the animal and human studies which have elucidated the roles of metformin, α-glucosidase inhibitors, glucagon-like peptide-1 agonists, peroxisome proliferator-activated receptors γ agonists, inhibitors of dipeptidyl peptidase-4, sodium/glucose cotransporter inhibitors, and other less studied medications on gut microbiota. This review is dedicated to one of the most widespread diseases, T2D, and the currently used antidiabetic drugs and most promising new findings. In general, the gut microbiota has been shown to have an influence on host metabolism, food consumption, satiety, glucose homoeostasis, and weight gain. Altered intestinal microbiota composition has been noticed in cardiovascular diseases, colon cancer, rheumatoid arthritis, T2D, and obesity. Therefore, the main effect of antidiabetic drugs is on the microbiome composition, basically increasing the short-chain fatty acids-producing bacteria, responsible for losing weight and suppressing inflammation.

Antioxidant, α-Amylase and α-Glucosidase Inhibitory Activities and Potential Constituents of Canarium tramdenum Bark

The fruits of Canarium tramdenum are commonly used as foods and cooking ingredients in Vietnam, Laos, and the southeast region of China, whilst the leaves are traditionally used for treating diarrhea and rheumatism. This study was conducted to investigate the potential use of this plant bark as antioxidants, and α-amylase and α-glucosidase inhibitors. Five different extracts of C. tramdenum bark (TDB) consisting of the extract (TDBS) and factional extracts hexane (TDBH), ethyl acetate (TDBE), butanol (TDBB), and water (TDBW) were evaluated. The TDBS extract contained the highest amount of total phenolic (112.14 mg gallic acid equivalent per g dry weight), while the TDBB extract had the most effective antioxidant capacity compared to other extracts. Its IC₅₀ values were 12.33, 47.87, 33.25, and 103.74 µg/mL in 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (ABTS), reducing power (RP), and nitric oxide (NO) assays, respectively. Meanwhile, the lipid peroxidation inhibition of the four above extracts was proximate to that of butylated hydroxytoluene (BHT) as a standard antioxidant. The result of porcine pancreatic α-amylase inhibition showed that TDB extracts have promising effects which are in line with the commercial diabetic inhibitor acarbose. Interestingly, the inhibitory ability on α-glucosidase of all the extracts was higher than that of acarbose. Among the extracts, the TDBB extract expressed the strongest activity on the enzymatic reaction (IC₅₀ = 18.93 µg/mL) followed by the TDBW extract (IC₅₀ = 25.27 µg/mL), TDBS (IC₅₀ = 28.17 µg/mL), and TDBE extract (IC₅₀ = 141.37 µg/mL). The phytochemical constituents of the TDB extract were identified by gas chromatography–mass spectrometry (GC-MS). The principal constituents included nine phenolics, eight terpenoids, two steroids, and five compounds belonging to other chemical classes, which were the first reported in this plant. Among them, the presence of α- and β-amyrins were identified by GC-MS and appeared as the most dominant constituents in TDB extracts (1.52 mg/g). The results of this study revealed that C. tramdenum bark possessed rich phenolics and terpenoids, which might confer on reducing risks from diabetes. A high quantity of α- and β-amyrins highlighted the potentials of anti-inflammatory, anti-ulcer, anti-hyperlipidemic, anti-tumor, and hepatoprotective properties of C. tramdenum bark.

peel based on rGO@Fe3O4 nanocomposites microreactor

Present study aimed to immobilise the α-glucosidase on suitable supports to construct enzymatic microreactors and their subsequent applicability in efficient inhibitor screening from the Chinese Yam (Dioscorea opposita Thunb.) peel. A type of lamellar and porous composites (rGO@Fe3O4) were synthesised with a facile one-step solvothermal method and employed as carriers to construct enzymatic microreactors for screening α-glucosidase ligand from the Chinese Yam peel in league with the high performance liquid chromatography and mass spectrometry (HPLC-MS). The immobilisation amount of α-glucosidase on rGO@Fe3O4 under the optimised conditions was about 40 μg α-glucosidase/mg carriers. Furthermore, the binding capacities of screened inhibitors, 2,4-dimethoxy-6,7-dihydroxyphenanthrene and batatasin I, were 35.6 and 68.2%, respectively. Hence, considering their high screening efficiency and excellent magnetic separation ability, these as-prepared nanocomposite consisting of rGO and Fe3O4 may be potential supports for the enzyme (such as α-glucosidase) immobilisation for rapid α-glucosidase inhibitors screening from the diverse nature resources.

Meroterpenoids and Isocoumarinoids from a Myrothecium Fungus Associated with Apocynum Venetum

Four new meroterpenoids 1⁻4 and four new isocoumarinoids 5⁻8, along with five known isocoumarinoids (9⁻13), were isolated from the fungus Myrothecium sp. OUCMDZ-2784 associated with the salt-resistant medicinal plant, Apocynum venetum (Apocynaceae). Their structures were elucidated by means of spectroscopic analysis, X-ray crystallography, ECD spectra and quantum chemical calculations. Compounds 1⁻5, 7, 9 and 10 showed weak α-glucosidase inhibition with the IC₅₀ values of 0.50, 0.66, 0.058, 0.20, 0.32, 0.036, 0.026 and 0.37 mM, respectively.

Characterization of α-Glucosidase Inhibitors from Clinacanthus nutans Lindau Leaves by Gas Chromatography-Mass Spectrometry-Based Metabolomics and Molecular Docking Simulation

BACKGROUND

Clinacanthus nutans (C. nutans) is an Acanthaceae herbal shrub traditionally consumed to treat various diseases including diabetes in Malaysia. This study was designed to evaluate the α-glucosidase inhibitory activity of C. nutans leaves extracts, and to identify the metabolites responsible for the bioactivity.

METHODS

Crude extract obtained from the dried leaves using 80% methanolic solution was further partitioned using different polarity solvents. The resultant extracts were investigated for their α-glucosidase inhibitory potential followed by metabolites profiling using the gas chromatography tandem with mass spectrometry (GC-MS).

RESULTS

Multivariate data analysis was developed by correlating the bioactivity, and GC-MS data generated a suitable partial least square (PLS) model resulting in 11 bioactive compounds, namely, palmitic acid, phytol, hexadecanoic acid (methyl ester), 1-monopalmitin, stigmast-5-ene, pentadecanoic acid, heptadecanoic acid, 1-linolenoylglycerol, glycerol monostearate, alpha-tocospiro B, and stigmasterol. In-silico study via molecular docking was carried out using the crystal structure Saccharomyces cerevisiae isomaltase (PDB code: 3A4A). Interactions between the inhibitors and the protein were predicted involving residues, namely LYS156, THR310, PRO312, LEU313, GLU411, and ASN415 with hydrogen bond, while PHE314 and ARG315 with hydrophobic bonding.

CONCLUSION

The study provides informative data on the potential α-glucosidase inhibitors identified in C. nutans leaves, indicating the plant's therapeutic effect to manage hyperglycemia.