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.

Design and semisynthesis of oleanolic acid derivatives as VEGF inhibitors: Inhibition of VEGF-induced proliferation, angiogenesis, and VEGFR2 activation in HUVECs.

Angiogenesis inhibitors targeting the VEGF signaling pathway are developed into drugs for the treatment of vaious diseases, such as cancer, rheumatoid arthritis, and age-related macular degeneration. Recent studies have revealed that oleanolic acid (OA), a natural pentacyclic triterpenoid, inhibited the VEGF/VEGFR2 signaling pathway and angiogenesis in HUVECs, which may represent an attractive VEGF inhibitor. In this paper, rational structural modification towards OA was performed in order to improve its inhibitory effects aganist VEGF and anti-angiogenesis potential. As a result, a series of novel OA derivatives, possessing α,ß-unsaturated ketone system in ring A and amide functional group at C-28, were prepared and evaluated for cytotoxicity and their ability to inhibit VEGF-induced abnormal proliferation of HUVECs. The results showed that two promising derivatives, OA-1 and OA-16, exhibited no in vitro cytotoxicity against HUVECs but showed more potent inhibitory activity against VEGF-induced proliferation and angiogenesis in HUVECs, compared with OA. The results of Western blot indicated that OA-1 and OA-16 inhibited VEGF-induced VEGFR2 activation. Furthermore, small interfering RNA experiments were performed to confirm that both compounds inhibited VEGF-induced angiogenesis via VEGFR2. Thus, the present study resulted in the discovery of new promising OA-inspired VEGF inhibitors, which can serve as potential lead compounds for the treatment of angiogenesis-related diseases.

Design, synthesis and biological evaluation of marine phidianidine-inspired derivatives against oxidized ldl-induced endothelial injury by activating Nrf2 anti-oxidation pathway.

Inhibition of oxidized low-density lipoprotein (oxLDL)-induced vascular endothelial cell (VEC) injury is one of the effective strategies for treating atherosclerosis. In the present study, a series of novel marine phidianidine-inspired indole-1,2,4-oxadiazoles was designed, synthesized, and evaluated for their effects against oxLDL-induced injury in VECs. Among them, compound D-6, displaying the most effective protective activity, was found to inhibit oxLDL-induced apoptosis and the expression of ICAM-1 and VCAM-1 in VECs. Mechanistic studies showed that D-6 could trigger Nrf2 nuclear translocation, subsequently resulting in increased expression of Nrf2 target gene HO-1. Meanwhile, D-6 suppressed the increase of ROS level and nuclear translocation of NF-κB induced by oxLDL. Importantly, Nrf2 knockdown attenuated the inhibition effects of D-6 on oxLDL-induced apoptosis, ROS production and NF-κB nuclear translocation. Collectively, our studies demonstrated that compound D-6 protected against oxLDL-induced endothelial injury by activating Nrf2/HO-1 anti-oxidation pathway.

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.

A highly sensitive endoplasmic reticulum-targeting fluorescent probe for the imaging of endogenous H2S in live cells.

Hydrogen sulfide (H2S) as an important signaling biomolecule participates in a series of complex physiological and pathological processes. In situ and rapid detection of H2S levels in endoplasmic reticulum (ER) is of great importance for the in-depth study of its virtual functional roles. However, the ER-targeting fluorescent probe for the detection of H2S in live cells is still quite rare. Herein, a new ER-targeting fluorescent probe (FER-H2S) for detecting H2S in live cells was characterized in the present study. This probe FER-H2S was built from the hybridization of three parts, including fluorescein-based skeleton, p-toluenesulfonamide as ER-specific group, and 2,4-nitrobenzene sulfonate as a response site for H2S. The response mechanism of the probe FER-H2S to H2S is on the basis of the ring-opening and ring-closing processes in fluorescein moiety. Moreover, the probe FER-H2S was successfully used for the imaging of exogenous and endogenous H2S in ER of live cells.