Synthesis and biological evaluation of GPR40/FFAR1 agonists containing 3,5-dimethylisoxazole

Synthesis, biological activities, and evaluation molecular docking-dynamics studies of new phenylisoxazole quinoxalin-2-amine hybrids as potential α-amylase and α-glucosidase inhibitors

New phenylisoxazole quinoxalin-2-amine hybrids 5a-i were successfully synthesised with yields of 53-85% and characterised with various spectroscopy methods. The synthesised hybrids underwent in vitro α-amylase and α-glucosidase inhibitory assays, with acarbose as the positive control. Through the biological study, compound 5h exhibits the highest α-amylase inhibitory activity with IC50 = 16.4 ± 0.1 μM while compounds 5a-c, 5e and 5h exhibit great potential as α-glucosidase inhibitors, with 5c being the most potent (IC50 = 15.2 ± 0.3 μM). Among the compounds, 5h exhibits potential as a dual inhibitor for both α-amylase (IC50 = 16.4 ± 0.1 μM) and α-glucosidase (IC50 = 31.6 ± 0.4 μM) enzymes. Through the molecular docking studies, the inhibition potential of the selected compounds is supported. Compound 5h showed important interactions with α-amylase enzyme active sites and exhibited the highest binding energy of -8.9 ± 0.10 kcal mol-1, while compound 5c exhibited the highest binding energy of -9.0 ± 0.20 kcal mol-1 by forming important interactions with the α-glucosidase enzyme active sites. The molecular dynamics study showed that the selected compounds exhibited relative stability when binding with α-amylase and α-glucosidase enzymes. Additionally, compound 5h demonstrated a similar pattern of motion and mechanism of action as the commercially available miglitol.

Synthesis, biological evaluation, and molecular modelling of novel quinoxaline-isoxazole hybrid as anti-hyperglycemic

In our effort to develop potent anti-hyperglycemic compounds with inhibitory activity against α-amylase and α-glucosidase, a series of novel quinoxaline-isoxazole moieties were synthesized. The novel quinoxaline-isoxazole derivatives were assessed in vitro for their anti-hyperglycemic activities on α-amylase and α-glucosidase inhibitions. The results revealed promising IC50 values compared to acarbose as a positive control for α-amylase and α-glucosidase. Among them, N-Ethyl-7-chloro-3-((3-phenylisoxazol-5-yl)methoxy)quinoxalin-2-amine 5b showed dual inhibitory with IC50 of 24.0 µM for α-amylase and 41.7 µM for α-glucosidase. In addition, N-Ethyl-7-methoxy-3-((3-(2-chlorophenyl)isoxazol-5-yl)methoxy)quinoxalin-2-amine 5j also had dual bioactivities against α-amylase and α-glucosidase with IC50 of 17.0 and 40.1 µM, respectively. Nevertheless, two more compounds N-Ethyl-7-cyano-3-((3-phenylisoxazol-5-yl)methoxy)quinoxaline-2-amine 5e showed strong mono-inhibition for α-glucosidase with IC50 of 16.6 µM followed by N-Ethyl-7-methoxy-3-((3-phenylisoxazol-5-yl)methoxy)quinoxalin-2-amine 5 f with IC50 of 18.6 µM. The molecular docking study for α-glucosidase inhibitor provided the binding energy ranging from 8.3 to 9.1 kcal/mol and α-amylase inhibitor showed the binding energy score at 8.4 and 8.5 kcal/mol. The dual inhibitions nature of 5b and 5j were further analyzed and confirmed via molecular dynamics including the stability of the compound, interaction energy, binding free energy, and the interaction residue analysis using the MM-GBSA approach. The results showed that compound 5j was the most potent compound. Lastly, the drug-likeness properties were also evaluated with all synthesized compounds 5a-5j and the results reveal that all potent compounds meet Lipinski's rules of five.

Recent Updates on Free Fatty Acid Receptor 1 (GPR-40) Agonists for the Treatment of Type 2 Diabetes Mellitus

BACKGROUND

The global incidence of type 2 diabetes mellitus (T2DM) has enthused the development of new antidiabetic targets with low toxicity and long-term stability. In this respect, free fatty acid receptor 1 (FFAR1), which is also recognized as a G protein-coupled receptor 40 (GPR40), is a novel target for the treatment of T2DM. FFAR1/GPR40 has a high level of expression in β-cells of the pancreas, and the requirement of glucose for stimulating insulin release results in immense stimulation to utilise this target in the medication of T2DM.

METHODS

The data used for this review is based on the search of several scienctific databases as well as various patent databases. The main search terms used were free fatty acid receptor 1, FFAR1, FFAR1 agonists, diabetes mellitus, G protein-coupled receptor 40 (GPR40), GPR40 agonists, GPR40 ligands, type 2 diabetes mellitus and T2DM.

RESULTS

The present review article gives a brief overview of FFAR1, its role in T2DM, recent developments in small molecule FFAR1 (GPR40) agonists reported till now, compounds of natural/plant origin, recent patents published in the last few years, mechanism of FFAR1 activation by the agonists, and clinical status of the FFAR1/GPR40 agonists.

CONCLUSION

The agonists of FFAR1/GRP40 showed considerable potential for the therapeutic control of T2DM. Most of the small molecule FFAR1/GPR40 agonists developed were aryl alkanoic acid derivatives (such as phenylpropionic acids, phenylacetic acids, phenoxyacetic acids, and benzofuran acetic acid derivatives) and thiazolidinediones. Some natural/plant-derived compounds, including fatty acids, sesquiterpenes, phenolic compounds, anthocyanins, isoquinoline, and indole alkaloids, were also reported as potent FFAR1 agonists. The clinical investigations of the FFAR1 agonists demonstrated their probable role in the improvement of glucose control. Though, there are some problems still to be resolved in this field as some FFAR1 agonists terminated in the late phase of clinical studies due to "hepatotoxicity." Currently, PBI-4050 is under clinical investigation by Prometic. Further investigation of pharmacophore scaffolds for FFAR1 full agonists as well as multitargeted modulators and corresponding clinical investigations will be anticipated, which can open up new directions in this area.

Design, synthesis and biological evaluation of novel FFA1/GPR40 agonists: New breakthrough in an old scaffold

Based on an old phenoxyacetic acid scaffold, CPU014 (compound 14) has been identified as a superior agonist by comprehensive exploration of structure-activity relationship. In vitro toxicity study suggested that CPU014 has lower risk of hepatotoxicity than TAK-875. During acute toxicity study (5-500 mg/kg), a favorable therapeutic window of CPU014 was observed by evaluation of plasma profiles and liver slices. Moreover, CPU014 promotes insulin secretion in a glucose-dependent manner, while no GLP-1 secretion has been enhanced. Other than good pharmacokinetic properties, CPU014 significantly improved glucose tolerance both in normal and diabetic models without the risk of hypoglycemia. These subversive findings provided a safer candidate CPU014, which is currently in preclinical study to assess its potential for the treatment of diabetes.

Current anti-diabetic agents and their molecular targets: A review

Diabetes mellitus is a medical condition characterized by the body's loss of control over blood sugar. The frequency of diagnosed cases and consequential increases in medical costs makes it a rapidly growing chronic disease that threatens human health worldwide. In addition, its unnerving statistical projections are perilous to both the economy of the nation and man's life expectancy. Type-I and type-II diabetes are the two clinical forms of diabetes mellitus. Type-II diabetes mellitus (T2DM) is illustrated by the abnormality of glucose homeostasis in the body, resulting in hyperglycemia. Although significant research attention has been devoted to the development of diabetes regimens, which demonstrates success in lowering blood glucose levels, their efficacies are unsustainable due to undesirable side effects such as weight gain and hypoglycemia. Over the years, heterocyclic scaffolds have been the basis of anti-diabetic chemotherapies; hence, in this review we consolidate the use of bioactive scaffolds, which have been evaluated for their biological response as inhibitors against their respective anti-diabetic molecular targets over the past five years (2012-2017). Our investigation reveals a diverse target set which includes; protein tyrosine phosphatase 1 B (PTP1B), dipeptidly peptidase-4 (DPP-4), free fatty acid receptors 1 (FFAR1), G protein-coupled receptors (GPCR), peroxisome proliferator activated receptor-γ (PPARγ), sodium glucose co-transporter-2 (SGLT2), α-glucosidase, aldose reductase, glycogen phosphorylase (GP), fructose-1,6-bisphosphatase (FBPase), glucagon receptor (GCGr) and phosphoenolpyruvate carboxykinase (PEPCK). This review offers a medium on which future drug design and development toward diabetes management may be modelled (i.e. optimization via structural derivatization), as many of the drug candidates highlighted show promise as an effective anti-diabetic chemotherapy.

Metal-free direct C-arylation of 1,3-dicarbonyl compounds and ethyl cyanoacetate: a platform to access diverse arrays of meta-functionalized phenols

A base mediated, highly convenient strategy for the direct C-arylation of 1,3-dicarbonyls and cyanoacetate with various phenol derivatives as aryl partners is presented.

Isoxazole ring as a useful scaffold in a search for new therapeutic agents

Due to its relatively easy synthesis, isoxazole ring has been as an object of interest for chemists and pharmacologists from research groups all over the world. Its chemical modifications include both connection of isoxazole with other aromatic, heteroaromatic or non aromatic rings and substitution with different alkyl groups. Thanks to their usually low cytotoxicity, isoxazole derivatives are still popular scaffolds for the development of new agents with variable biological activities, such as antimicrobial, antiviral, anticancer, anti-inflammatory, immunomodulatory, anticonvulsant or anti-diabetic properties. This review discusses the chemical structure of recently developed isoxazole derivatives with regards to their activity and potential therapeutic use.

Ligands at Free Fatty Acid Receptor 1 (GPR40)

FFA1 is a G protein-coupled receptor activated by medium- to long-chain fatty acids. FFA1 plays important roles in various physiological processes such as insulin secretion and energy metabolism. FFA1 expressed on pancreatic β-cells and intestine contributes to insulin and incretin secretion, respectively. These physiological functions of FFA1 are interesting as an attractive drug target for type II diabetes and metabolic disorders. A number of synthetic FFA1 ligands have been developed and they have contributed to our current understanding of the physiological and pathophysiological functions of FFA1 both in in vitro and in vivo studies. In addition, these synthetic ligands also provided information on the structure-activity relationships of FFA1 ligands. Further, FFA1 protein crystallized with one of the high affinity agonist leads provided useful insights for the development of more effective ligands. Among FFA1 ligands, several compounds have been further investigated in the clinical trials. Thus, FFA1 ligands have great potential as drug candidates. In this section, recent progress about FFA1 ligands and the possibility of their clinical use are described.