New cycloalkyl[b]thiophenylnicotinamide-based α-glucosidase inhibitors as promising anti-diabetic agents: Synthesis, in silico study, in vitro and in vivo evaluations.

In the present study, a series of cycloalkyl[b]thiophenylnicotinamide derivatives against α-glucosidase were synthesized, and evaluated for their in vitro and in vivo anti-diabetic potential. Most of the synthetic analogues exhibited superior α-glucosidase inhibitory effects than the standard drug acarbose (IC50 = 258.5 µM), in which compound 11b with cyclohexyl[b]thiophene core demonstrated the highest activity with an IC50 value of 9.9 µM and showed higher selectivity towards α-glucosidase over α-amylase by 7.4-fold. Fluorescence quenching experiment confirmed the direct binding of 11b with α-glucosidase, kinetics study revealed that 11b was a mixed-type inhibitor, and its binding mode was analyzed using molecular docking. Moreover, analogs compounds 6a-9b, 11b, 12b did not show in vitro cytotoxicity against LO2 and HepG2 cells. Finally, compound 11b exhibited in vivo hypoglycemic activity by reducing the blood glucose levels in sucrose-loaded rats.

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.

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.

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 New Endoplasmic Reticulum (ER)-Targeting Fluorescent Probe for the Imaging of Cysteine in Living Cells.

Cysteine (Cys) is an important endogenous amino acid and plays critical physiological roles in living systems. Herein, an endoplasmic reticulum (ER)-targeting fluorescent probe (FER-Cys) was designed and prepared for imaging of Cys in living cells. The probe FER-Cys consists of a fluorescein framework as the fluorescent platform, acrylate group as the response site for the selective recognition of Cys, and ER-specific p-toluenesulfonamide fragment. After the response of probe FER-Cys to Cys, a turn-on fluorescence signal at 546 nm could be detected obviously. The probe FER-Cys further shows desirable selectivity to Cys. Finally, the probe FER-Cys was proven to selectively detect Cys in live cells and successfully image the changes of Cys level in the cell models of H2O2-induced redox imbalance.

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.

New cinnamic acid-pregenolone hybrids as potential antiproliferative agents: Design, synthesis and biological evaluation.

A series of new cinnamic acid-pregenolone hybrids (5a-5o) was designed, synthesized and evaluated for their in vitro antiproliferative activity. Some of them showed potential antiproliferative activity and selectivity towards a panel of cancer cell lines, including A549, H157, HepG2, MCF-7, and HL-60. Among these analogs, compound 5f showed the most promising activity with IC50 values ranging from 3.2 to 6.8 µM, and it was taken as a model compound in the following antiproliferative mechanism study. In Hoechst 33258 staining assay, 5f-treated A549 cells displayed significant apoptosis characteristics. Flow cytometry analysis revealed that 5f showed the antiproliferative activity against A549 via G1 cell cycle arrest and inducing apoptosis. Western blotting analysis demonstrated that 5f enhanced apoptosis of A549 cells by down-regulating Bcl-2 and up-regulating Bax protein expression. The present study highlighted this series of cinnamic acid-pregenolone hybrids as a new antiproliferative lead prototype.

Discovery of New Selective Butyrylcholinesterase (BChE) Inhibitors with Anti-Aß Aggregation Activity: Structure-Based Virtual Screening, Hit Optimization and Biological Evaluation.

In this study, a series of selective butyrylcholinesterase (BChE) inhibitors was designed and synthesized from the structural optimization of hit 1, a 4-((3,4-dihydroisoquinolin-2(1H)-yl)methyl)benzoic acid derivative identified by virtual screening our compound library. The in vitro enzyme assay results showed that compounds 9 ((4-((3,4-dihydroisoquinolin-2(1H)-yl)methyl)phenyl)(pyrrolidin-1-yl)methanone) and 23 (N-(2-bromophenyl)-4-((3,4-dihydroisoquinolin-2(1H)-yl)methyl)benzamide) displayed improved BChE inhibitory activity and good selectivity towards BChE versus AChE. Their binding modes were probed by molecular docking and further validated by molecular dynamics simulation. Kinetic analysis together with molecular modeling studies suggested that these derivatives could target both the catalytic active site (CAS) and peripheral anionic site (PAS) of BChE. In addition, the selected compounds 9 and 23 displayed anti-Aß1-42 aggregation activity in a dose-dependent manner, and they did not show obvious cytotoxicity towards SH-SY5Y neuroblastoma cells. Also, both compounds showed significantly protective activity against Aß1-42-induced toxicity in a SH-SY5Y cell model. The present results provided a new valuable chemical template for the development of selective BChE inhibitors.

Discovery of new multifunctional selective acetylcholinesterase inhibitors: structure-based virtual screening and biological evaluation.

Although the mechanism of Alzheimer's disease (AD) is still not fully understood, the development of multifunctional AChE inhibitors remains a research focus for AD treatment. In this study, 48 AChE candidate inhibitors were picked out from SPECS database through a pharmacophore- and molecular docking-based virtual screening. The biological evaluation results indicated that four compounds 7, 29, 41 and 48 with different scaffolds exhibited potent and selective AChE inhibitory activity, with the best IC50 value of 1.62 ± 0.11 µM obtained for 48. Then their mechanism of action, the inhibition on Aß aggregation, neurotoxicity, and neuroprotective activity against Aß-induced nerve cell injury were well studied. The binding mode of 48 with AChE was also proposed. The present bioassay results indicated that these multifunctional AChE inhibitors were worth for further structural derivatization to make them the anti-AD lead compounds.