Synthesis and alpha-D-glucosidase inhibitory activity of N-substituted valiolamine derivatives as potential oral antidiabetic agents

Design and evaluation of curcumin-derived aldopentose compounds: Unlocking their antidiabetic potential through integrative in vitro, in vivo, and in silico studies on carbohydrate-degrading enzymes

Natural polyphenol compounds such as curcumin can inhibit carbohydrate-hydrolyzing enzymes, which may offer an alternative to expensive and potentially side-effect-inducing α-glucosidase inhibitors like acarbose. Hence, this study carried out the synthesis of curcumin aldopentose derivatives, examining their capacity to inhibit the α-glucosidase and α-amylase enzymes with the aim to alleviate hyperglycemia. Initially, the aldopentose derivatives from curcumin were synthesized and confirmed by spectroscopic methods such as MS, 13CNMR, 1HNMR, and FTIR. Afterward, we investigated the inhibitory effects of all derivatives on the α-amylase and α-glucosidase enzymes spectroscopically and determined their inhibition mechanism. We assessed the antioxidant activity and the stability of the synthetic derivatives in the simulated intestinal environment. Finally, we measured the postprandial blood glucose level after administering saturated starch in vivo. The modified compounds showed improved inhibitory effects compared to curcumin alone, with compound C3 demonstrating particularly strong enzyme inhibition. However, when compared with acarbose, a known commercial antidiabetic drug, the synthetic compounds showed lower inhibitory activity against both enzymes, resulting in fewer side effects related to undigested polysaccharides in the gut. Molecular docking studies show introducing a pentose moiety to the curcumin backbone enhanced docking affinities toward both enzymes and subsequently altered the associated IC50 and Ki values. Overall, compound C3 has the potential to be an inhibitor of carbohydrate-degrading enzymes and can effectively reduce glucose absorption in vivo. Given its antioxidant capabilities and reasonable stability, the compound in question shows promises as a potent derivative for the development of new anti-hyperglycemic drugs in future research endeavours.

Data on the docking of millet-derived secondary metabolites as multi-target ligands for diabetes

The deterioration of human health due to unhealthy lifestyle and dietary habits has led to a worldwide increase in various metabolic diseases that significantly affect public health. Diabetes is one of the most serious health problems, is caused by abnormal metabolic processes and is becoming increasingly common. According to World Health Organisation (WHO) reports, a significant proportion of the world's population suffers from these diseases and their incidence continues to rise at an alarming rate. These metabolic disorders are characterised by elevated blood sugar levels, which serve as a warning sign for a variety of other health problems. Factors contributing to these diseases include a high-fat diet, insufficient physical activity, genetic predisposition, lack of exercise and underlying diseases. Diabetes mellitus, a fast-growing chronic metabolic disease, is characterised by insufficient insulin production by the pancreas or the body's inability to use insulin action. Various strategies are recommended by health and nutrition experts to manage this condition, including lifestyle changes, exercise, low-carbohydrate and low-fat diets and intermittent fasting. In cases where these measures prove insufficient, medication may be prescribed. However, the development of multi-drug therapies for metabolic disorders has proven to be an attractive field for pharmacists as they address several diseases simultaneously. Despite the promising effects of multi-drug therapies, the high costs and potential side effects associated with recently developed drugs necessitate alternative approaches. The utilisation of natural bioactive compounds from plant extracts represents a promising high-throughput strategy. This approach utilises network pharmacology and screening methods to identify potential ligands that act as inhibitors for the treatment of complex, interconnected diseases. In the current investigation, we used a molecular docking approach to investigate secondary metabolites from millet as potential multi-target ligands for the treatment of diabetes and obesity.

Synthesis of (+)-Voglibose

A concise asymmetric synthesis of voglibose, a natural product derivative and an alpha-glucosidase inhibitor with antihyperglycemic activity, was produced from an O-arylated lactic acid derivative in only seven steps. This approach was based on an oxidative phenol dearomatization process promoted by a hypervalent iodine reagent, a chiral auxiliary serving as a protecting group and allowing the asymmetric formation of the target, and a key hydrolysis leading to the formation of several contiguous stereocenters and removal of the chiral auxiliary.

Comparative Study on the Hypoglycemic Effects of Different Parts of Musa balbisiana

Diabetes mellitus is a chronic metabolic disorder that can cause elevated blood glucose levels due to impaired insulin secretion or resistance. Different parts of Musa balbisiana have been used widely in traditional medicine to treat many disorders. The present study aims to evaluate the antidiabetic ability of the corm, pseudostem, inflorescence, fruit, peel, and seed of M. balbisiana via in vitro experiments by inhibiting α-amylase and α-glucosidase enzymes as well as in vivo models on diabetic alloxan-induced mice. The results show that all investigated parts have performed potential inhibition on two investigated digestive enzymes. Seed poses the highest capacity among surveyed parts on α-amylase (IC50:f μg/mL) and α-glucosidase (IC50: 21.63 μg/mL) as well as effectively lowers the blood glucose index (IG) in alloxan-induced mice. In addition, fruit, corm, and inflorescence are considered essential parts that have high hypoglycemic effects via in vivo experiments. These findings indicate that all M. balbisiana parts are possibly a potential source for hypoglycemic agents; further clinical studies are needed to evaluate the safety of human beings before applying them in functional food and pharmaceutical industries.

Enzyme Activity Inhibition of α-Amylase Using Molecularly Imprinted Polymer (MIP) Hydrogel Microparticles

Molecularly imprinted polymers (MIPs) are a class of synthetic recognition materials that offer a cost-effective and robust alternative to antibodies. While MIPs have found predominant use in biosensing and diagnostic applications, their potential for alternative uses, such as enzyme inhibition, remains unexplored. In this work, we synthesized a range of acrylamide-based hydrogel MIP microparticles (35 μm) specific for the recognition of α-amylase. These MIPs also showed good selectivity toward the target protein with over 96% binding of the target protein, compared with the control nonimprinted polymer (NIP) counterparts. Specificity of the MIPs was determined with the binding of nontarget proteins, trypsin, human serum albumin (HSA), and bovine serum albumin (BSA). The MIPs were further evaluated for their ability to inhibit α-amylase enzymatic activity, showing a significant decrease in activity. These findings highlight the potential of MIPs as enzyme inhibitors, suggesting an innovative application beyond their conventional use.

Dipeptidyl-peptidase 4 (DPP4) mediates fatty acid uptake inhibition by glucose via TAS1R3 and GLUT-2 in Caco-2 enterocytes

Both high glucose intake with a high-fat meal and inhibition of dipeptidyl peptidase-4 (DPP4) have been associated with plasma lipid-lowering effects, but mechanistic understanding linking glucose and fat absorption is lacking. We here hypothesized that glucose ameliorates intestinal fatty acid uptake via a pathway involving DPP4. A concentration of 50 mM glucose reduced mean DPP4 activity in differentiated Caco-2 enterocytes by 42.5 % and fatty acid uptake by 66.0 % via nutrient sensing by the sweet taste receptor subunit TAS1R3 and glucose transporter GLUT-2. No effect of the DPP4 substrates GLP-1 and GIP or of the cellular energy status on the reduced uptake of fatty acids was seen, but a direct interaction between DPP4 and fatty acid transporters is suggested. Conclusively we identified DPP4 as a regulator of fatty acid absorption in Caco-2 enterocytes that mediates the inhibition of intestinal fatty acid uptake by glucose via an interplay of GLUT-2 and TAS1R3.

Diversification of Simple Arenes into Complex (Amino)cyclitols

Highly oxygenated cyclohexanes, including (amino)cyclitols, are featured in natural products possessing a notable range of biological activities. As such, these building blocks are valuable tools for medicinal chemistry. While de novo synthetic strategies have provided access to select compounds, challenges including stereochemical density and complexity have hindered the development of a general approach to (amino)cyclitol structures. This work reports the use of arenophile chemistry to access dearomatized intermediates which are amenable to diverse downstream transformations. Practical guidelines were developed for the synthesis of natural and non-natural (amino)cyclitols from simple arenes through a series of strategic functionalization events.

New Insights into the Latest Advancement in α-Amylase Inhibitors of Plant Origin with Anti-Diabetic Effects

The rising predominance of type 2 diabetes, combined with the poor medical effects seen with commercially available anti-diabetic medications, has motivated the development of innovative treatment approaches for regulating postprandial glucose levels. Natural carbohydrate digestion enzyme inhibitors might be a viable option for blocking dietary carbohydrate absorption with fewer side effects than manufactured medicines. Alpha-amylase is a metalloenzyme that facilitates digestion by breaking down polysaccharides into smaller molecules such as maltose and maltotriose. It also contributes to elevated blood glucose levels and postprandial hyperglycemia. As a result, scientists are being urged to target α-amylase and create inhibitors that can slow down the release of glucose from carbohydrate chains and prolong its absorption, thereby resulting in lower postprandial plasma glucose levels. Natural α-amylase inhibitors derived from plants have gained popularity as safe and cost-effective alternatives. The bioactive components responsible for the inhibitory actions of various plant extracts have been identified through phytochemical research, paving the way for further development and application. The majority of the findings, however, are based on in vitro investigations. Only a few animal experiments and very few human investigations have confirmed these findings. Despite some promising results, additional investigation is needed to develop feasible anti-diabetic drugs based on plant-derived pancreatic α-amylase inhibitors. This review summarizes the most recent findings from research on plant-derived pancreatic α-amylase inhibitors, including plant extracts and plant-derived bioactive compounds. Furthermore, it offers insights into the structural aspects of the crucial therapeutic target, α-amylases, in addition to their interactions with inhibitors.

Chemoselective Nozaki-Hiyama-Takai-Kishi and Grignard reaction: short synthesis of some carbahexopyranoses

A common, divergent, efficient, stereoselective and short approach for the total syntheses of some carbahexopyranoses namely, MK7607, (-)-gabosine A, (-)-conduritol E, (-)-conduritol F, 6a-carba-β-d-fructopyranose and other carbasugars using chemoselective Grignard or Nozaki-Hiyama-Takai-Kishi (NHTK) reactions and RCM. Herein, the Grignard and NHTK reactions are able to differentiate the reactivity difference between lactol or lactolacetate and aldehyde of 2 & 6 under given conditions to give the desired skeleton chemoselectivity.

Metabolites extracted from microorganisms as potential inhibitors of glycosidases (α-glucosidase and α-amylase): A review

α-Glucosidase and α-amylase are the two main glycosidases that participate in the metabolism of carbohydrates. Inhibitors of these two enzymes are considered an important medical treatment for carbohydrate uptake disorders, such as diabetes and obesity. Microbes are an important source of constituents that have the potential to inhibit glycosidases and can be used as sources of new drugs and dietary supplements. For example, the α-glucosidase inhibitor acarbose, isolated from Actinoplanes sp., has played an important role in adequately controlling type 2 diabetes, but this class of marketed drugs has many drawbacks, such as poor compliance with treatment and expense. This demonstrates the need for new microorganism-derived resources, as well as novel classes of drugs with better compliance, socioeconomic benefits, and safety. This review introduces the literature on microbial sources of α-glucosidase and α-amylase inhibitors, with a focus on endophytes and marine microorganisms, over the most recent 5 years. This paper also reviews the application of glycosidase inhibitors as drugs and dietary supplements. These studies will contribute to the future development of new microorganism-derived glycosidase inhibitors.

Recent Updates on Phytoconstituent Alpha-Glucosidase Inhibitors: An Approach towards the Treatment of Type Two Diabetes

Diabetes is a common metabolic disorder marked by unusually high plasma glucose levels, which can lead to serious consequences such as retinopathy, diabetic neuropathy and cardiovascular disease. One of the most efficient ways to reduce postprandial hyperglycemia (PPHG) in diabetes mellitus, especially insulin-independent diabetes mellitus, is to lower the amount of glucose that is absorbed by inhibiting carbohydrate hydrolyzing enzymes in the digestive system, such as α-glucosidase and α-amylase. α-Glucosidase is a crucial enzyme that catalyzes the final stage of carbohydrate digestion. As a result, α-glucosidase inhibitors can slow D-glucose release from complex carbohydrates and delay glucose absorption, resulting in lower postprandial plasma glucose levels and control of PPHG. Many attempts have been made in recent years to uncover efficient α-glucosidase inhibitors from natural sources to build a physiologic functional diet or lead compound for diabetes treatment. Many phytoconstituent α-glucosidase inhibitors have been identified from plants, including alkaloids, flavonoids, anthocyanins, terpenoids, phenolic compounds, glycosides and others. The current review focuses on the most recent updates on different traditional/medicinal plant extracts and isolated compounds' biological activity that can help in the development of potent therapeutic medications with greater efficacy and safety for the treatment of type 2 diabetes or to avoid PPHG. For this purpose, we provide a summary of the latest scientific literature findings on plant extracts as well as plant-derived bioactive compounds as potential α-glucosidase inhibitors with hypoglycemic effects. Moreover, the review elucidates structural insights of the key drug target, α-glucosidase enzymes, and its interaction with different inhibitors.

Diverse gallotannins with α-glucosidase and α-amylase inhibitory activity from the roots of Euphorbia fischeriana steud

A phytochemical investigation of the roots of Euphorbia fischeriana Steud. led to the isolation of eleven undescribed gallotannins, fishertannins A-K, together with four known analogues. Their structures were elucidated by the comprehensive spectroscopic data including UV, IR, HR-ESI-MS, and NMR, while the absolute configurations of the sugar moiety were determined by the acid hydrolysis and HPLC analyses. Fishertannin A possessed an unusual skeleton comprised of acetophenone, galloyl group, arabinofuranosyl and glucopyranosyl moieties. Fishertannin B, fishertannin H, fishertannin K, 1,2,3-tri-O-galloyl-β-D-glucopyranose, 3,4,6-tri-O-galloyl-D-glucopyranose, and 1,6-di-O-galloyl-β-D-glucopyranose displayed the potent α-glucosidase inhibitory activities with the IC₅₀ values of 15.48-177.13 μM. Examination of the structure-activity relationships (SAR) demonstrated that the galloyl and glucopyranosyl moieties played a key role in the inhibitory activity for both α-glucosidase and α-amylase inhibitory activity. Among all isolates, 1,2,3-tri-O-galloyl-β-D-glucopyranose showed the most potent and highly specific inhibitory activity against α-glucosidase with an IC₅₀ value of 15.48 ± 0.60 μM. The kinetic analysis of 1,2,3-tri-O-galloyl-β-D-glucopyranose disclosed the mixed inhibition type on α-glucosidase, and the molecular docking visualized the stable binding with the catalytic pocket of α-glucosidase (pdb 3A4A). These findings indicated the excellent antidiabetic potential of the gallotannins from E. fischeriana, while 1,2,3-tri-O-galloyl-β-D-glucopyranose could be developed as a promising candidate for the treatment of T2DM with fewer side effects.

Anti-diabetic potential of Urtica Dioica: current knowledge and future direction

Aim

This review summarizes studies on the anti-diabetic effect of Urtica Dioica (UD) in Type-2-diabetes.

Materials and methods

We studied worldwide traditional medicines, old texts, and published literature for anti-diabetic effect of UD. Electronic databases comprising PubMed, Web of Science, Science Direct, Scopus and Google Scholar were searched to collect articles published between 1990 and 2021 years.

Results

Our literature investigation suggests UD as a glucose lowering, blood lipid regulating, anti-inflammatory and anti-oxidation plant.

Conclusions

UD's anti-diabetic properties make it potential traditional therapeutics for lowering the clinical manifestations of T2DM through affecting hyperglycemia and therefore suggest it as a proper medication with no or limited side effects.

Design and synthesis of biologically active carbaglycosylamines: From glycosidase inhibitors to pharmacological chaperones

For over 50 years, our group has been involved in synthetic studies on biologically active cyclitols including carbasugars. Among a variety of compounds synthesized, this review focuses on carbaglycosylamine glycosidase inhibitors, highlighting the following: (1) the naturally occurring N-linked carbaoligosaccharide α-amylase inhibitor acarbose and related compounds; (2) the novel synthetic β-glycosidase inhibitors, 1'-epi-acarviosin and its 6-hydroxy analogue as well as β-valienaminylceramide and its 4'-epimer; (3) the discovery of the β-glycosidase inhibitors with chaperone activity, N-octyl-β-valienamine (NOV) and its 4-epimer (NOEV); and (4) the recent development of the potential pharmacological chaperone N-alkyl-conduramine F-4 derivatives.

Benzodioxole grafted spirooxindole pyrrolidinyl derivatives: synthesis, characterization, molecular docking and anti-diabetic activity

A highly stereoselective, three-component method has been developed to synthesize pyrrolidine and pyrrolizidine containing spirooxindole derivatives. The interaction between the dipolarophile α,β-unsaturated carbonyl compounds and the dipole azomethine ylide formed in situ by the reaction of 1,2-dicarbonyl compounds and secondary amino acids is referred to as the 1,3-dipolar cycloaddition reaction. The reaction conditions were optimized to achieve excellent stereo- and regioselectivity. Shorter reaction time, simple work-up and excellent yields are the salient features of the present approach. Various spectroscopic methods and single crystal X-ray diffraction examinations of one example of compound 6i validated the stereochemistry of the expected products. The anti-diabetic activity of the newly synthesized spirooxindole derivatives was tested against the α-glucosidase and α-amylase enzymes. Compound 6i was found to exhibit potent inhibition activity against α-glucosidase and α-amylase enzymes which is further evidenced by molecular docking studies.

A highly stereoselective, three-component method has been developed for the synthesis of pyrrolidine and pyrrolizidine containing spirooxindole derivatives that exhibits excellent anti-diabetic activity.

N-Substituted Valiolamine Derivatives as Potent Inhibitors of Endoplasmic Reticulum α-Glucosidases I and II with Antiviral Activity

Most enveloped viruses rely on the host cell endoplasmic reticulum (ER) quality control (QC) machinery for proper folding of glycoproteins. The key ER α-glucosidases (α-Glu) I and II of the ERQC machinery are attractive targets for developing broad-spectrum antivirals. Iminosugars based on deoxynojirimycin have been extensively studied as ER α-glucosidase inhibitors; however, other glycomimetic compounds are less established. Accordingly, we synthesized a series of N-substituted derivatives of valiolamine, the iminosugar scaffold of type 2 diabetes drug voglibose. To understand the basis for up to 100,000-fold improved inhibitory potency, we determined high-resolution crystal structures of mouse ER α-GluII in complex with valiolamine and 10 derivatives. The structures revealed extensive interactions with all four α-GluII subsites. We further showed that N-substituted valiolamines were active against dengue virus and SARS-CoV-2 in vitro. This study introduces valiolamine-based inhibitors of the ERQC machinery as candidates for developing potential broad-spectrum therapeutics against the existing and emerging viruses.

A Review on Antidiabetic Activity of Centaurea spp.: A New Approach for Developing Herbal Remedies

Objective

Diabetes mellitus (DM) is a long-life metabolic disorder, characterized by high blood glucose levels. The hyperglycemic condition generally leads to irreversible nerve injury and vascular damage. Among different types of diabetes, type 2 is more common and has spread all over the world. Although various therapeutic approaches have been developed to control type 2 DM, regulating blood glucose levels has still remained a controversial challenge for patients. Also, most prescription drugs cause different side effects, such as gastrointestinal disorders. Thus, developing novel and efficient antidiabetic agents possessing fewer adverse effects is in high demand.

Method

The literature was comprehensively surveyed via search engines such as Google Scholar, PubMed, and Scopus using appropriate keywords.

Results

Medicinal plants, both extracts and isolated active components, have played a significant role in controlling the blood glucose levels. Good-to-excellent results documented in the literature have made them a precious origin for developing and designing drugs and supplements against DM. Centaurea spp. have been traditionally used for controlling high blood glucose levels. Also, the antidiabetic properties of different species of Centaurea have been confirmed in recent studies through in vitro assays as well as in vivo experiments.

Conclusion

Potent results encouraged us to review their efficacy to open a new horizon for development of herbal antidiabetic agents.

Antioxidant and glycohydrolase inhibitory behavior of curcumin-based compounds: Synthesis and evaluation of anti-diabetic properties in vitro

Naturally occurring anti-diabetic compound curcumin can prevent diabetes complications due to antioxidant and anti-inflammatory properties as well as the attenuation of postprandial hyperglycemia. In this line, we have synthesized thirteen curcumin based derivatives (L1-L13) by multi-component reaction, characterized by IR, 1HNMR, 13C NMR, MS, elemental analysis and evaluated for possible antioxidant properties and α-glucosidase (α-Glu) and α-amylase (α-Amy) inhibitory potential. The curcumin-based pyrano[2,3-d]pyrimidine derivatives could inhibit α-Glu and α-Amy enzyme activity which showed desirable antioxidant activity. Furthermore, among the series, L5, L12, L9, L10, L8 and L11 were identified as more potent inhibitors of α-Glu enzyme than curcumin and the compounds of L12, L4, L9, L5, L10, L8, L13, and L11 were the stronger inhibitors of the α-Amy enzyme in vitro. Besides, among them, L12 had the lowest IC50 for the inhibition of both enzymes. Since strong inhibitors for pancreatic α-Amy result in the progression of severe gastrointestinal side effects, the inhibitors that show the lower α-Amy/α-Glu inhibitory ratio have attracted much attention in medicinal chemistry. Besides, considering antioxidant characteristics of synthesized compounds, the L7 derivative with the highest antioxidant activity and the lowest "α-Amy/α-Glu inhibitory" ratio could be an appropriate candidate for further study through the rational drug design to the exploration of a new class of powerful anti-diabetic drugs.

Curcumin-based Antioxidant and Glycohydrolase Inhibitor Compounds: Synthesis and In Vitro Appraisal of the Dual Activity Against Diabetes

BACKGROUND

Curcumin, as the substantial constituent of the turmeric plant (Curcuma longa), plays a significant role in the prevention of various diseases, including diabetes. It possesses ideal structure features as an enzyme inhibitor, including a flexible backbone, hydrophobic nature, and several available hydrogen bond (H-bond) donors and acceptors.

OBJECTIVE

The present study aimed at synthesizing several novel curcumin derivatives and further evaluation of these compounds for possible antioxidant and anti-diabetic properties along with inhibitory effect against two carbohydrate-hydrolyzing enzymes, α-amylase and α-glucosidase, as these enzymes are therapeutic targets for attenuation of postprandial hyperglycemia.

METHODS

Therefore, curcumin-based pyrido[2,3-d]pyrimidine derivatives were synthesized and identified using an instrumental technique like NMR spectroscopy and then screened for antioxidant and enzyme inhibitory potential. Total antioxidant activity, reducing power assay and 1,1-diphenyl-2- picrylhydrazyl (DPPH•) radical scavenging activity were done to appraise the antioxidant potential of these compounds in vitro.

RESULTS

Compounds L6-L9 showed higher antioxidant activity while L4, L9, L12 and especially L8 exhibited the best selectivity index (lowest α-amylase/α-glucosidase inhibition ratio).

CONCLUSION

These antioxidant inhibitors may be potential anti-diabetic drugs, not only to reduce glycemic index but also to limit the activity of the major reactive oxygen species (ROS) producing pathways.

Inhibitors of α-amylase and α-glucosidase: Potential linkage for whole cereal foods on prevention of hyperglycemia

The strategy of reducing carbohydrate digestibility by controlling the activity of two hydrolyzing enzymes (α-amylase and α-glucosidase) to control postprandial hyperglycemia is considered as a viable prophylactic treatment of type 2 diabetes mellitus (T2DM). Thus, the consumption of foods rich in hydrolyzing enzyme inhibitors is recommended for diet therapy of diabetes. Whole cereal products have gained increasing interests for plasma glucose-reducing effects. However, the mechanisms for whole cereal benefits in relation to T2DM are not yet fully understood, but most likely involve bioactive components. Cereal-derived phenolic compounds, peptides, nonstarch polysaccharides, and lipids have been shown to inhibit α-amylase and α-glucosidase activities. These hydrolyzing enzyme inhibitors seem to make whole cereals become nutritional strategies in managing postmeal glucose for T2DM. This review presents an updated overview on the effects provided by cereal-derived ingredients on carbohydrate digestibility. It suggests that there is some evidence for whole cereal intake to be beneficial in amelioration of T2DM through inhibiting α-glucosidase and α-amylase activities.

Structural Dependence of Sulfated Polysaccharide for Diabetes Management: Fucoidan From Undaria pinnatifida Inhibiting α-Glucosidase More Strongly Than α-Amylase and Amyloglucosidase

Fucoidan refers to a group of sulfated polysaccharide that is commonly obtained from various species of brown seaweed. Fucoidan has gained increased popularity among researchers in the recent years due to its numerous biological activities, including its inhibitory effects against starch hydrolyzing enzymes such as α-amylase and α-glucosidase. This highlights the potential of fucoidan as an antidiabetic agent in the management and prevention of diabetes mellitus. In this study, the inhibitory effects of fucoidan isolated from the New Zealand Undaria pinnatifida seaweed species against three starch hydrolyzing enzymes—α-amylase, α-glucosidase, and amyloglucosidase—was investigated. It was demonstrated that while the fucoidan exhibited significant inhibitory effects against all the three starch hydrolases, it is an uncompetitive inhibitor of α-amylase and amyloglucosidase, and is a competitive inhibitor of α-glucosidase. Moreover, it exhibited significantly stronger inhibitory effects against α-glucosidase than α-amylase, thus having the desirable characteristics as an antidiabetic agent.

Stereoselective synthesis of (+)-5-thiosucrose and (+)-5-thioisosucrose

(+)-5-Thiosucrose 1, a novel isosteric sulfur analog of sucrose, was synthesized stereoselectively for the first time via indirect β-d-fructofuranosidation involving selective β-d-psicofuranosidation, followed by stereo-inversion of the secondary hydroxy group at the C-3 position on the furanose ring. Glycosidation of protected 5-thio-d-glucose with a d-psicofuranosyl donor provided β-d-psicofuranosyl 5-thio-α-d-glucopyranoside and that with d-fructofuranosyl donor gave α-d-fructofuranosyl 5-thio-α-d-glucopyranoside. Two anomeric stereocenters of the glycosyl donor and acceptor were controlled correctly to provide a single disaccharide among four possible anomeric isomers in the glycosylation. Conversion of the resulting disaccharides afforded (+)-5-thiosucrose 1 and (+)-5-thioisosucrose 2 in excellent yields, respectively. Inhibitory activities of 1 and 2 against α-glucosidase in vitro were also examined.

In Vitro Studies of Fermented Korean Chung-Yang Hot Pepper Phenolics as Inhibitors of Key Enzymes Relevant to Hypertension and Diabetes

This study was investigated to evaluate the antioxidant activity, the angiotensin I-converting enzyme (ACE) inhibition effect, and the α-amylase and α-glucosidase inhibition activities of hot pepper water extracts both before and after their fermentation. The fermented pepper water extract (FP) showed significantly higher total phenol content, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical inhibition effect, metal chelating activity and ACE inhibition activity compared to the non-fermented raw pepper water extract (RP) (p < 0.05). Meanwhile, the FP showed lower α-amylase and higher α-glucosidase inhibitory activities, but the RP showed similar levels of α-amylase and α-glucosidase inhibitory activities. Taken together, these results suggested that fermented pepper extract using water should be expected to have potentially inhibitory effects against both hyperglycemia and hypertension.

Chain-Branched Polyhydroxylated Octahydro-1H-Indoles as Potential Leads against Lysosomal Storage Diseases

Here, the synthesis and glycosidase inhibition properties of the two first known 3-ethyloctahydro-1H-indole-4,5,6-triols are reported. This study shows the transformation of d-glucose into polyhydroxylated 1-(2-nitrocyclohexane) acetaldehydes, followed by a protocol involving the formation of the azacyclopentane ring. Results of inhibitory potency assays and docking calculations show that at least one of them could be a lead for optimization in the search for compounds that behave like folding chaperones in lysosomal storage diseases.

Biosynthesis and Metabolic Engineering of Pseudo-oligosaccharides

Pseudo-oligosaccharides are microbial-derived secondary metabolites whose chemical structures contain pseudosugars (glycomimetics). Due to their high resemblance to the molecules of life (carbohydrates), most pseudo-oligosaccharides show significant biological activities. Some of them have been used as drugs to treat human and plant diseases. Because of their significant economic value, efforts have been put into understanding their biosynthesis, optimizing their fermentation conditions, and engineering their metabolic pathways to obtain better production yields. A number of unusual enzymes participating in diverse biosynthetic pathways to pseudo-oligosaccharides have been reported. Various methods and conditions to improve the production yields of the target compounds and eliminate byproducts have also been developed. This review article describes recent studies on the biosynthesis, fermentation optimization, and metabolic engineering of high-value pseudo-oligosaccharides.

Antidiabetic and antiparasitic potentials: Inhibition effects of some natural antioxidant compounds on α-glycosidase, α-amylase and human glutathione S-transferase enzymes

The glutathione S-transferase (GST) was purified from fresh blood erythrocytes using affinity column chromatography. Also, α-amylase from porcine pancreas and α-glycosidase from Saccharomyces cerevisiae were used as target enzymes. In this study, these compounds were tested on α-amylase, α-glycosidase, and GST enzymes and demonstrated effective inhibitor compounds with K_i values in the range of 8.34-40.78 μM against GST, and 120.53-892.36 nM against α-glycosidase. Additionally, the phenolic molecules were tested for the inhibition of α-amylase enzyme which determined effective inhibition profile with IC₅₀ values in the range of 175.01-626.58 nM. Indeed, these molecules can be elective inhibitors of GST, α-glycosidase and α-amylase enzymes as antidiabetic and antiparasitic agents.

Highly functionalized pyrrolidine analogues: stereoselective synthesis and caspase-dependent apoptotic activity

Spiropyrrolidines were synthesized employing a new class of azomethine ylide for the first time and were tested for their anticancer activity, where the cell death mechanism revealed that it is occurring through the caspase-3 dependent pathway.

Divergent synthesis of new α-glucosidase inhibitors obtained through a vinyl Grignard-mediated carbocyclisation

Four new α-glucosidase inhibitors have been synthesised through 5–8 synthetic steps from a common synthetic intermediate obtained through a recently developed carbocyclisation.

A Simple Representation of Three-Dimensional Molecular Structure

Statistical and machine learning approaches predict drug-to-target relationships from 2D small-molecule topology patterns. One might expect 3D information to improve these calculations. Here we apply the logic of the extended connectivity fingerprint (ECFP) to develop a rapid, alignment-invariant 3D representation of molecular conformers, the extended three-dimensional fingerprint (E3FP). By integrating E3FP with the similarity ensemble approach (SEA), we achieve higher precision-recall performance relative to SEA with ECFP on ChEMBL20 and equivalent receiver operating characteristic performance. We identify classes of molecules for which E3FP is a better predictor of similarity in bioactivity than is ECFP. Finally, we report novel drug-to-target binding predictions inaccessible by 2D fingerprints and confirm three of them experimentally with ligand efficiencies from 0.442-0.637 kcal/mol/heavy atom.

Synthesis of novel dispiro[indazole-5,3′-pyrrolidine-2′,3″-indole] derivatives via 1,3-dipolar cycloaddition of azomethine ylide

The 1,3-dipolar cycloaddition of azomethine ylide, generated in situ from isatin and sarcosine, to 5-arylmethylidene-1-phenyl-6,7-dihydro-1 H-indazol-4(5 H)-ones afforded novel 1′-methyl-4′-aryl-1-phenyl-6,7-dihydrodispiro[indazole-5,3′-pyrrolidine-2′,3″-indole]-2″,4(1 H,1″ H)-diones in moderate yields. The structures of all the products were characterised thoroughly by NMR, IR, HRMS, together with X-ray crystallographic analysis.

C-5a-substituted validamine type glycosidase inhibitors

A series of N-alkyl derivatives of the D-galactosidase inhibitor 1,4-di-epi-validamine featuring lipophilic substituents at position C-5a was prepared and screened for their glycosidase inhibitory properties. Products turned out selective for β-galactosidases as well as β-glucosidases.

One-pot cis-selective route to sugar-fused thiazines via a masking–unmasking strategy in basic ionic liquid

A novel sequential Knoevenagel condensation, thia-Michael, and amino/mercaptoacetylative ring transformation reaction cascade for cis-selective synthesis of sugar-fused 1,3-thiazine is reported. The expeditious one-pot multicomponent annulation was performed using masked amino acid viz. 2-phenyl-1,3-oxazol-5-one or masked mercaptoacid viz. 2-methyl-2-phenyl-1,3-oxathiolan-5-one, d-xylose/d-glucose, and N-aryldithiocarbamic acid in ionic liquid [bmim]OH. The acetophenone obtained as a by-product and [bmim]OH itself could be easily recycled for further use without loss of efficiency. The envisaged method is operationally simple, high yielding, and excellent diastereoselective in favor of the cis-isomer of fused thiazines.

Biosynthesis and Biological Activity of Carbasugars

The first synthesis of carbasugars, compounds in which the ring oxygen of a monosaccharide had been replaced by a methylene moiety, was described in 1966 by Professor G. E. McCasland’s group. Seven years later, the first true natural carbasugar (5a-carba-R-D-galactopyranose) was isolated from a fermentation broth of Streptomyces sp. MA-4145. In the following decades, the chemistry and biology of carbasugars have been extensively studied. Most of these compounds show interesting biological properties, especially enzymatic inhibitory activities, and, in consequence, an important number of analogues have also been prepared in the search for improved biological activities. The aim of this review is to give coverage on the progress made in two important aspects of these compounds: the elucidation of their biosynthesis and the consideration of their biological properties, including the extensively studied carbapyranoses as well as the much less studied carbafuranoses.