Investigation of pyrazolo[1,5-a]quinoxalin-4-ones as novel monoamine oxidase inhibitors

Recent updates on structural insights of MAO-B inhibitors: a review on target-based approach

Parkinson's disease is a neurodegenerative disorder characterized by slow movement, tremors, and stiffness caused due to loss of dopaminergic neurons caused in the brain's substantia nigra. The concentration of dopamine is decreased in the brain. Parkinson's disease may be happened because of various genetic and environmental factors. Parkinson's disease is related to the irregular expression of the monoamine oxidase (MAO) enzyme, precisely type B, which causes the oxidative deamination of biogenic amines such as dopamine. MAO-B inhibitors, available currently in the market, carry various adverse effects such as dizziness, nausea, vomiting, lightheadedness, fainting, etc. So, there is an urgent need to develop new MAO-B inhibitors with minimum side effects. In this review, we have included recently studied compounds (2018 onwards). Agrawal et al. reported MAO-B inhibitors with IC50 0.0051 µM and showed good binding affinity. Enriquez et al. reported a compound with IC50 144 nM and bind with some critical amino acid residue Tyr60, Ile198, and Ile199. This article also describes the structure-activity relationship of the compounds and clinical trial studies of related derivatives. These compounds may be used as lead compounds to develop potent compounds as MAO-B inhibitors.

Selegiline ameliorated dyslipidemia and hepatic steatosis in high-fat diet mice

Certain monoamine oxidase (MAO) inhibitors exhibit beneficial effects, such as reducing adiposity and metabolic disorders; however, their effects on hepatic lipid metabolism have not been revealed. This study aimed to investigate the effects of a selective MAO-B inhibitor, selegiline, on dyslipidemia and hepatic steatosis in mice induced by a high-fat diet (HFD). Administration of selegiline (0.6 mg/kg body weight) by intraperitoneal injection was found to reduce HFD-induced body weight gain and increases in liver and adiposity coefficients, blood lipids and fatty acid levels. Furthermore, selegiline dramatically reduced the total triglyceride (TG) and cholesterol (TC) levels and lipid accumulation in the livers of HFD-fed mice and palmitic acid (PA)-treated AML-12 hepatocytes. In vivo and in vitro results indicated that selegiline protects against HFD- and PA-induced hepatic inflammation by reducing the expression of proinflammatory cytokines, namely IL-6, TNF-α, IL-1β, and IL-1α. Additionally, selegiline exhibited antioxidative effects on HFD and PA exposure in mouse liver and AML-12 cells by decreasing the levels of reactive oxygen species (ROS) and malonaldehyde (MDA) and increasing superoxide dismutase (SOD) activity. Further study showed that selegiline administration mitigated the expression of Srebf-1, Fasn, and Acaca and downregulated the expression of Cpt-1 and Pparα in HFD-fed mouse livers and PA-treated AML-12 cells. In conclusion, our findings suggest that selegiline exerts protective effects against HFD-induced dyslipidemia and hepatic steatosis, which may be related to an improved inflammatory response, oxidative stress, and hepatic lipid metabolism.

3-(3,4-Dichlorophenyl)-5-(1H-indol-5-yl)-1,2,4-oxadiazole

3-(3,4-Dichlorophenyl)-5-(1H-indol-5-yl)-1,2,4-oxadiazole was synthesized via the condensation of 3,4-dichlorobenzamidoxime and methyl 1H-indole-5-carboxylate using a superbasic medium (NaOH/DMSO). The compound was tested as a potential inhibitor of human monoamine oxidase (MAO) A and B. It demonstrated a notable inhibition with an IC50 value of 0.036 μM for the MAO-B and isoform specificity. The product was characterized by 1H-NMR, 13C-NMR, and HRMS. In conclusion, the new active MAO-B inhibitor may serve as a candidate for the future discovery of therapeutic agents for neurodegenerative disorders such as Parkinson’s disease.

Copper-Catalyzed Oxidative [3 + 2]-Annulation of Quinoxalin-2(1H)-one with Oxime Esters toward Functionalized Pyrazolo[1,5-a]quinoxalin-4(5H)-ones as Opioid Receptor Modulators

Pyrazolo[1,5-a]quinoxalin-4(5H)-one derivatives as novel opioid receptor modulators have been synthesized via copper-catalyzed oxidative [3 + 2]-annulation of quinoxalin-2(1H)-one and oxime-O-acetates. This hydrazine-free C-C and N-N bond formation strategy starts with the generation of C₂N₁ synthon using oxime acetate, which reacts in a [3 + 2] manner with quinoxalin-2(1H)-one, followed by oxidative aromatization. The synthesized compounds were tested against opioid receptors, of which eight compounds exhibited an antagonistic effect with EC₅₀ < 5 μM at various opioid receptors. Molecular docking studies were performed to identify the binding of active pyrazolo[1,5-a]quinoxalin-4(5H)-one ligands with hKOR protein. Docking results indicated that compounds 3d and 3g participate in hydrogen bonding with the hydroxyl group of T111 of the active site pocket residue.

Synthesis and Photoluminescent Properties of 2-(3-Carboxymethylindazol-1-yl)anilines

Abstract

A two-stage method for the preparation of 2-(3-carboxymethylindazol-1-yl)anilines using the N-arylation reaction of 3-carboxymethylindazoles with o-nitrohaloarenes and subsequent reduction of nitro-containing intermediates with tin(II) chloride was developed. The experimental results showed that the use of the synthesized compounds as fluorophores in the visible region of the spectrum is promising.