Fluorescent-tagged sp2-iminosugars with potent β-glucosidase inhibitory activity

Synthesis and Biological Evaluation of New Dihydrofuro[3,2-b]piperidine Derivatives as Potent α-Glucosidase Inhibitors

Inhibition of glycoside hydrolases has widespread application in the treatment of diabetes. Based on our previous findings, a series of dihydrofuro[3,2-b]piperidine derivatives was designed and synthesized from D- and L-arabinose. Compounds 32 (IC50 = 0.07 μM) and 28 (IC50 = 0.5 μM) showed significantly stronger inhibitory potency against α-glucosidase than positive control acarbose. The study of the structure-activity relationship of these compounds provides a new clue for the development of new α-glucosidase inhibitors.

Design, synthesis and biological evaluation of novel (E)-2-benzylidene-N-(3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophen-2-yl)hydrazine-1-carboxamide derivatives as α-glucosidase inhibitors

In this present study, a series of novel (E)-2-benzylidene-N-(3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophen-2-yl)hydrazine-1-carboxamide derivatives against α-glucosidase were designed and synthesized, and their biological activities were evaluated in vitro and in vivo. Most of the designed analogues exhibited better inhibitory activity than the marketed acarbose, especially the most potent compound 7 with an IC₅₀ value of 9.26 ± 1.84 μM. The direct binding of 7 and 8 with α-glucosidase was confirmed by fluorescence quenching experiments, and the kinetic and molecular docking studies revealed that 7 and 8 inhibited α-glucosidase in a non-competitive manner. Cytotoxicity bioassay indicated compounds 7 and 8 were non-toxic towards LO2 and HepG2 at 100 μM. Furthermore, both compounds were demonstrated to have in vivo hypoglycemic activity by reducing the blood glucose levels in sucrose-treated rats.

Discovery of new 2-phenyl-1H-benzo[d]imidazole core-based potent α-glucosidase inhibitors: Synthesis, kinetic study, molecular docking, and in vivo anti-hyperglycemic evaluation

In the present study, a series of 2-phenyl-1H-benzo[d]imidazole-based α-glucosidase inhibitors were synthesized and evaluated for their in vitro and in vivo anti-diabetic potential. Screening of an in-house library revealed a moderated α-glucosidase inhibitor, 6a with 3-(1H-benzo[d]imidazol-2-yl)aniline core, and then the structural optimization was performed to obtain more efficient derivatives. Most of these derivatives showed increased activity than 6a, and the most promising inhibitors were found to be compounds 15o and 22d with IC₅₀ values of 2.09 ± 0.04 and 0.71 ± 0.02 µM, respectively. Fluorescence quenching experiment confirmed the direct binding of compounds 15o and 22d with α-glucosidase. Kinetic study revealed that both compounds were non-competitive inhibitors, that was consistent with the result of molecular docking studies where they located at the allosteric site of the enzyme. Cell viability evaluation demonstrated the non-cytotoxicity of 15o and 22d against LO2 cells. Furthermore, the in vivo pharmacodynamic study revealed that compound 15o showed significant hypoglycemic activity and improved oral sucrose tolerance, comparable to the positive control acarbose.

Novel tetrahydrobenzo[b]thiophen-2-yl)urea derivatives as novel α-glucosidase inhibitors: Synthesis, kinetics study, molecular docking, and in vivo anti-hyperglycemic evaluation

α-Glucosidase inhibitors, which can inhibit the digestion of carbohydrates into glucose, are one of important groups of anti-type 2 diabetic drugs. In the present study, we report our effort on the discovery and optimization of α-glucosidase inhibitors with tetrahydrobenzo[b]thiophen-2-yl)urea core. Screening of an in-house library revealed a moderated α-glucosidase inhibitors, 5a, and then the following structural optimization was performed to obtain more efficient derivatives. Most of these derivatives showed increased inhibitory activity against α-glucosidase than the parental compound 5a (IC₅₀ of 26.71 ± 1.80 μM) and the positive control acarbose (IC₅₀ of 258.53 ± 1.27 μM). Among them, compounds 8r (IC₅₀ = 0.59 ± 0.02 μM) and 8s (IC₅₀ = 0.65 ± 0.03 μM) were the most potent inhibitors, and showed selectivity over α-amylase. The direct binding of both compounds with α-glucosidase was confirmed by fluorescence quenching experiments. Kinetics study revealed that these compounds were non-competitive inhibitors, which was consistent with the molecular docking results that compounds 8r and 8s showed high preference to bind to the allosteric site instead of the active site of α-glucosidase. In addition, compounds 8r and 8s were not toxic (IC₅₀ > 100 μM) towards LO2 and HepG2 cells. Finally, the in vivo anti-hyperglycaemic activity assay results indicated that compounds 8r could significantly decrease the level of plasma glucose and improve glucose tolerance in SD rats treated with sucrose. The present study provided the tetrahydrobenzo[b]thiophen-2-yl)urea chemotype for developing novel α-glucosidase inhibitors against type 2 diabetes.

Discovery of New α-Glucosidase Inhibitors: Structure-Based Virtual Screening and Biological Evaluation

α-Glycosidase inhibitors could inhibit the digestion of carbohydrates into glucose and promote glucose conversion, which have been used for the treatment of type 2 diabetes. In the present study, 52 candidates of α-glycosidase inhibitors were selected from commercial Specs compound library based on molecular docking–based virtual screening. Four different scaffold compounds (7, 22, 37, and 44) were identified as α-glycosidase inhibitors with IC₅₀ values ranging from 9.99 to 35.19 μM. All these four compounds exerted better inhibitory activities than the positive control (1-deoxynojirimycin, IC₅₀ = 52.02 μM). The fluorescence quenching study and kinetic analysis revealed that all these compounds directly bind to α-glycosidase and belonged to the noncompetitive α-glycosidase inhibitors. Then, the binding modes of these four compounds were carefully investigated. Significantly, these four compounds showed nontoxicity (IC₅₀ > 100 μM) toward the human normal hepatocyte cell line (LO2), which indicated the potential of developing into novel candidates for type 2 diabetes treatment.

Mechanistic Insights into the Chaperoning of Human Lysosomal-Galactosidase Activity: Highly Functionalized Aminocyclopentanes and C-5a-Substituted Derivatives of 4-epi-Isofagomine

Glycosidase inhibitors have shown great potential as pharmacological chaperones for lysosomal storage diseases. In light of this, a series of new cyclopentanoid β-galactosidase inhibitors were prepared and their inhibitory and pharmacological chaperoning activities determined and compared with those of lipophilic analogs of the potent β-d-galactosidase inhibitor 4-epi-isofagomine. Structure-activity relationships were investigated by X-ray crystallography as well as by alterations in the cyclopentane moiety such as deoxygenation and replacement by fluorine of a “strategic” hydroxyl group. New compounds have revealed highly promising activities with a range of β-galactosidase-compromised human cell lines and may serve as leads towards new pharmacological chaperones for G_M1-gangliosidosis and Morquio B disease.

Probing the Inhibitor versus Chaperone Properties of sp²-Iminosugars towards Human β-Glucocerebrosidase: A Picomolar Chaperone for Gaucher Disease

A series of sp²-iminosugar glycomimetics differing in the reducing or nonreducing character, the configurational pattern (d-gluco or l-ido), the architecture of the glycone skeleton, and the nature of the nonglycone substituent has been synthesized and assayed for their inhibition properties towards commercial glycosidases. On the basis of their affinity and selectivity towards GH1 β-glucosidases, reducing and nonreducing bicyclic derivatives having a hydroxylation profile of structural complementarity with d-glucose and incorporating an N′-octyl-isourea or -isothiourea segment were selected for further evaluation of their inhibitory/chaperoning potential against human glucocerebrosidase (GCase). The 1-deoxynojirimycin (DNJ)-related nonreducing conjugates behaved as stronger GCase inhibitors than the reducing counterparts and exhibited potent chaperoning capabilities in Gaucher fibroblasts hosting the neuronopathic G188S/G183W mutation, the isothiourea derivative being indeed one of the most efficient chaperone candidates reported up to date (70% activity enhancement at 20 pM). At their optimal concentration, the four selected compounds promoted mutant GCase activity enhancements over 3-fold; yet, the inhibitor/chaperoning balance became unfavorable at much lower concentration for nonreducing as compared to reducing derivatives.

Conformationally-locked N-glycosides: exploiting long-range non-glycone interactions in the design of pharmacological chaperones for Gaucher disease

Pyranoid-type glycomimetics having a cis-1,2-fused glucopyranose-2-alkylsulfanyl-1,3-oxazoline (Glc-PSO) structure exhibit an unprecedented specificity as inhibitors of mammalian β-glucosidase. Notably, their inhibitory potency against human β-glucocerebrosidase (GCase) was found to be strongly dependent on the nature of aglycone-type moieties attached at the sulfur atom. In the particular case of ω-substituted hexadecyl chains, an amazing influence of the terminal group was observed. A comparative study on a series of Glc-PSO derivatives suggests that hydrogen bond acceptor functionalities, e.g. fluoro or methyloxycarbonyl, significantly stabilize the Glc-PSO:GCase complex. The S-(16-fluorohexadecyl)-PSO glycomimetic turned out to be a more potent GCase competitive inhibitor than ambroxol, a non glycomimetic drug currently in pilot trials as a pharmacological chaperone for Gaucher disease. Moreover, the inhibition constant increased by one order of magnitude when shifting from neutral (pH 7) to acidic (pH 5) media, a favorable characteristic for a chaperone candidate. Indeed, the fluoro-PSO derivative also proved superior to ambroxol in mutant GCase activity enhancement assays in N370S/N370S Gaucher fibroblasts. The results presented here represent a proof of concept of the potential of exploiting long-range non-glycone interactions for the optimization of glycosidase inhibitors with chaperone activity.

Synthesis and biological evaluation of oleanolic acid derivative–chalcone conjugates as α-glucosidase inhibitors

Series of oleanolic acid derivative–chalcone conjugates were designed, synthesized and their α-glucosidase inhibitory activities were investigatedin vitro.

Bicyclic derivatives of L-idonojirimycin as pharmacological chaperones for neuronopathic forms of Gaucher disease

New human β-glucocerebrosidase (GCase) ligands with rigid 1,6-anhydro-β-L-idonojirimycin cores have been designed with the aid of molecular modeling. Efficient pharmacological chaperones for the L444P (trafficking-incompetent) mutant GCase enzyme associated with type 2 and 3 Gaucher disease (GD) were identified.

Conformationally-locked N-glycosides with selective β-glucosidase inhibitory activity: identification of a new non-iminosugar-type pharmacological chaperone for Gaucher disease

A series of conformationally locked N-glycosides having a cis-1,2-fused pyranose-1,3-oxazoline-2-thione structure and bearing different substituents at the exocyclic sulfur has been prepared. The polyhydroxylated bicyclic system was built in only three steps by treatment of the corresponding readily available 1,2-anhydrosugar with KSCN using TiO(TFA)(2) as catalyst, followed by S-alkylation and acetyl deprotection. In vitro screening against several glycosidase enzymes showed highly specific inhibition of mammalian β-glucosidase with a marked dependence of the potency upon the nature of the exocyclic substituent. The most potent representative, bearing an S-(ω-hydroxyhexadecyl) substituent, was further assayed as inhibitor of the human lysosomal β-glucocerebrosidase and as pharmacological chaperone in Gaucher disease fibroblasts. Activity enhancements in N370S/N370S mutants analogous to those achieved with the reference compound ambroxol were attained with a more favorable chaperone/inhibitor balance.

A convenient route to diversely substituted icosahedral closomer nanoscaffolds

The design and synthesis of icosahedral polyhedral borane closomer motifs based upon carbonate and carbamate anchoring groups for biomedical applications are described. Dodecacarbamate closomers containing easily accessible groups of interest at their linker termini were synthesized via activation of the B-OH vertices as aryl carbonates and their subsequent reaction with primary amines. Novel dodecacarbonate closomers were successfully synthesized for the first time by reacting [closo-B(12)(OH)(12)](2-) with an excess of respective aryl chloroformates, utilizing relatively short reaction times, mild conditions and simple purification strategies, all of which had previously presented difficulties in closomer chemistry. This methodology for the 12-fold degenerate synthesis of carbonate and carbamate closomers will greatly facilitate further exploration of closomers as monodisperse nanomolecular delivery platforms.

Imino sugars and glycosyl hydrolases: historical context, current aspects, emerging trends

Forty years of discoveries and research on imino sugars, which are carbohydrate analogues having a basic nitrogen atom instead of oxygen in the sugar ring and, acting as potent glycosidase inhibitors, have made considerable impact on our contemporary understanding of glycosidases. Imino sugars have helped to elucidate the catalytic machinery of glycosidases and have refined our methods and concepts of utilizing them. A number of new aspects have emerged for employing imino sugars as pharmaceutical compounds, based on their profound effects on metabolic activities in which glycosidases are involved. From the digestion of starch to the fight against viral infections, from research into malignant diseases to potential improvements in hereditary storage disorders, glycosidase action and inhibition are essential issues. This account aims at combining general developments with a focus on some niches where imino sugars have become useful tools for glycochemistry and glycobiology.