Design, synthesis and structure activity relationships of indazole and indole derivatives as potent glucagon receptor antagonists

Synthesis of 5-(trifluoroacetyl)imidazoles from Bromoenones and Benzimidamides via Aza-Michael Initiated Ring Closure Reaction

INTRODUCTION

A simple method for the preparation of 5-(trifluoroacetyl)imidazoles was elaborated.

METHODS

The reaction of trifluoromethyl(α-bromoalkenyl)ketones with benzimidamides was employed to afford the target heterocycles in good yields.

RESULTS

The assembly of imidazole core proceeds via aza-Michael adduct formation followed by intramolecular nucleophilic substitution and spontaneous aromatization as an oxidation sequence.

CONCLUSION

The yields of target imidazoles can be improved by the use of soft oxidizing agents.

In Vitro α-Glucosidase and α-Amylase Inhibition, Cytotoxicity and Free Radical Scavenging Profiling of the 6-Halogeno and Mixed 6,8-Dihalogenated 2-Aryl-4-methyl-1,2-dihydroquinazoline 3-Oxides

Series of the 6-bromo/iodo substituted 2-aryl-4-methyl-1,2-dihydroquinazoline-3-oxides and their mixed 6,8-dihalogenated (Br/I and I/Br) derivatives were evaluated for inhibitory properties against α-glucosidase and/or α-amylase activities and for cytotoxicity against breast (MCF-7) and lung (A549) cancer cell lines. The 6-bromo-2-phenyl substituted 3a and its corresponding 6-bromo-8-iodo-2-phenyl-substituted derivative 3i exhibited dual activity against α-glucosidase (IC50 = 1.08 ± 0.02 μM and 1.01 ± 0.05 μM, respectively) and α-amylase (IC50 = 5.33 ± 0.01 μM and 1.18 ± 0.06 μM, respectively) compared to acarbose (IC50 = 4.40 ± 0.05 μM and 2.92 ± 0.02 μM, respectively). The 6-iodo-2-(4-fluorophenyl)-substituted derivative 3f, on the other hand, exhibited strong activity against α-amylase and significant inhibitory effect against α-glucosidase with IC50 values of 0.64 ± 0.01 μM and 9.27 ± 0.02 μM, respectively. Compounds 3c, 3l and 3p exhibited the highest activity against α-glucosidase with IC50 values of 1.04 ± 0.03, 0.92 ± 0.01 and 0.78 ± 0.05 μM, respectively. Moderate cytotoxicity against the MCF-7 and A549 cell lines was observed for these compounds compared to the anticancer drugs doxorubicin (IC50 = 0.25 ± 0.05 μM and 0.36 ± 0.07 μM, respectively) and gefitinib (IC50 = 0.19 ± 0.04 μM and 0.25 ± 0.03 μM, respectively), and their IC50 values are in the range of 10.38 ± 0.08-25.48 ± 0.08 μM and 11.39 ± 0.12-20.00 ± 0.05 μM, respectively. The test compounds generally exhibited moderate to strong antioxidant capabilities, as demonstrated via robust free radical scavenging activity assays, viz., DPPH and NO. The potential of selected derivatives to inhibit superoxide dismutase (SOD) was also investigated via enzymatic assay in vitro. Molecular docking revealed the N-O moiety as essential to facilitate electrostatic interactions of the test compounds with the protein residues in the active site of α-glucosidase and α-amylase. The presence of bromine and/or iodine atoms resulted in increased hydrophobic (alkyl and/or π-alkyl) interactions and therefore increased inhibitory effect against both enzymes.

Extended Tripodal Hydrotris(indazol-1-yl)borate Ligands as Ruthenium-Supported Cogwheels for On-Surface Gearing Motions

This paper reports the synthesis of ruthenium-based molecular gear prototypes composed of a brominated or non-brominated pentaphenylcyclopentadienyl ligand as an anchoring unit and a tripodal ligand with aryl-functionalized indazoles as a rotating cogwheel. Single crystal structures of the ruthenium complexes revealed that the appended aryl groups increase the apparent diameter of the cogwheel rendering them larger than the diameter of the anchoring units and consequently making them suitable for intermolecular gearing motions once the complexes will be adsorbed on a surface.

Synthesis, α-amylase and α-glucosidase inhibition and molecular docking studies of indazole derivatives

Herein, we report the synthesis and inhibitory potential of indazole (Methyl 1H-indazole-4-carboxylate) derivatives (1-13) against α-amylase and α-glucosidase enzymes. The described derivatives demonstrated good inhibitory potential with IC₅₀ values, ranging between 15.04 ± 0.05 to 76.70 ± 0.06 µM ± SEM for α-amylase and 16.99 ± 0.19 to 77.97 ± 0.19 µM ± SEM for α-glucosidase, respectively. In particular, compounds (8-10 and 12) displayed significant inhibitory activities against both the screened enzymes, with their inhibitory potential comparable to the standard acarbose (12.98 ± 0.03 and 12.79 ± 0.17 µM ± SEM, respectively). Additionally, the influence of different substituents on enzyme inhibition activities was assessed to study the structure activity relationships. Molecular docking simulations were performed to rationalize the binding of derivatives/compounds with enzymes. All the synthesized derivatives (1-13) were characterized with the aid of spectroscopic instruments such as ¹H-NMR, ¹³C-NMR, HR-MS, elemental analysis and FTIR.Communicated by Ramaswamy H. Sarma.

Glucagon receptor signaling at white adipose tissue does not regulate lipolysis

Although the physiological role of glucagon receptor signaling in the liver is well defined, the impact of glucagon receptor (Gcgr) signaling on white adipose tissue (WAT) continues to be debated. Although numerous studies propose that glucagon stimulates WAT lipolysis, we lack evidence that physiological concentrations of glucagon regulate WAT lipolysis. In turn, we performed studies in both wild-type and WAT Gcgr knockout mice to determine if glucagon regulates lipolysis at WAT in the mouse. We assessed the effects of fasting and acute exogenous glucagon administration in wild-type C57BL/6J and Gcgr^Adipocyte+/+ versus Gcgr^Adipocyte-/- mice. Using an ex vivo lipolysis protocol, we further examined the direct effects of glucagon on physiologically (fasted) and pharmacologically stimulated lipolysis. We found that adipocyte Gcgr expression did not affect fasting-induced lipolysis or hepatic lipid accumulation in lean or diet-induced obese (DIO) mice. Acute glucagon administration did not affect serum nonesterified fatty acids (NEFA), leptin, or adiponectin concentration, but did increase serum glucose and FGF21, regardless of genotype. Glucagon did not affect ex vivo lipolysis in explants from either Gcgr^Adipocyte+/+ or Gcgr^Adipocyte-/- mice. Gcgr expression did not affect fasting-induced or isoproterenol-stimulated lipolysis from WAT explants. Moreover, glucagon receptor signaling at WAT did not affect body weight or glucose homeostasis in lean or DIO mice. Our studies have established that physiological levels of glucagon do not regulate WAT lipolysis, either directly or indirectly. Given that glucagon receptor agonism can improve dyslipidemia and decrease hepatic lipid accumulation, it is critical to understand the tissue-specific effects of glucagon receptor action. Unlike the crucial role of hepatic glucagon receptor signaling in maintaining glucose and lipid homeostasis, we observed no metabolic consequence of WAT glucagon receptor deletion.NEW & NOTEWORTHY It has been postulated that glucagon stimulates lipolysis and fatty acid release from white adipose tissue. We observed no metabolic effects of eliminating or activating glucagon receptor signaling at white adipose tissue.

Update of Indoles: Promising molecules for ameliorating metabolic diseases

Obesity and metabolic disorders have gradually become public health-threatening problems. The metabolic disorder is a cluster of complex metabolic abnormalities which are featured by dysfunction in glucose and lipid metabolism, and results from the increasing prevalence of visceral obesity. With the core driving factor of insulin resistance, metabolic disorder mainly includes type 2 diabetes mellitus (T2DM), micro and macro-vascular diseases, non-alcoholic fatty liver disease (NAFLD), dyslipidemia, and the dysfunction of gut microbiota. Strategies and therapeutic attention are demanded to decrease the high risk of metabolic diseases, from lifestyle changes to drug treatment, especially herbal medicines. Indole is a parent substance of numerous bioactive compounds, and itself can be produced by tryptophan catabolism to stimulate glucagon-like peptide-1 (GLP-1) secretion and inhibit the development of obesity. In addition, in heterocycles drug discovery, the indole scaffold is primarily found in natural compounds with versatile biological activity and plays a prominent role in drug molecules synthesis. In recent decades, plenty of natural or synthesized indole deriviatives have been investigated and elucidated to exert effects on regulating glucose hemeostasis and lipd metabolism. The aim of this review is to trace and emphasize the compounds containing indole scaffold that possess immense potency on preventing metabolic disorders, particularly T2DM, obesity and NAFLD, along with the underlying molecular mechanisms, therefore facilitate a better comprehension of their druggability and application in metabolic diseases.

Research progress of indole compounds with potential antidiabetic activity

New types of antidiabetic agents are continually needed with diabetes becoming the epidemic in the world. Indole alkaloids play an important role in natural products owing to their variable structures and versatile biological activities like anticonvulsant, anti-inflammatory, antidiabetic, antimicrobial, and anticancer activities, which are a promising source of novel antidiabetic drugs discovery. The synthesized indole derivatives possess similar properties to natural indole alkaloids. In the last two decades, more and more indole derivatives have been designed and synthesized for searching their bioactivities. This present review describes comprehensive structures of indole compounds with the potential antidiabetic activity including natural indole alkaloids and the synthetic indole derivatives based on the structure classification, summarizes their approaches isolated from natural sources or by synthetic methods, and discusses the antidiabetic effects and the mechanisms of action. Furthermore, this review also provides briefly synthetic procedures of some important indole derivatives.

Introducing new and effective catalysts for the synthesis of pyridazino[1,2-a]indazole, indazolo[2,1-b]phthalazine and pyrazolo[1,2-b]phthalazine derivatives

In this study, a new and effective catalyst for the synthesis of pyridazino[1,2-a]indazole, indazolo[2,1-b]phthalazine and pyrazolo[1,2-b]phthalazine derivatives was introduced. Triethanolammonium acetate ([TEAH][OAc]) accelerates the reaction in a one-pot and four-component condensation of aldehydes, hydrazine hydrate, succinic/phthalic anhydride, and 1,3-dicarbonyl compounds. The yield of the products is high, and the reaction conditions are mild and solvent-free. Furthermore, the model reaction was conducted in the presence of triethanolammonium sulphate ([TEAH][HSO₄] and triethanolammonium formate ([TEAH][HCOO]) under various conditions. In addition, the catalyst is recyclable, therefore, it can be reused several times. The structure of the obtained products was confirmed by comparing the M.P., IR, and ¹H NMR.

Advantages of this technique are as following:•

Synthesis of novel, green, and one-pot and four-component condensation (4CC) under solvent-free conditions at room temperature.

•

The catalytic reaction is performed under mild and environmentally friendly conditions in short reaction times and excellent yields.

•

The catalyst is easily recycled and exhibits good chemical and structural stability.