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.

Celastrol alleviates high-fat diet-induced obesity via enhanced muscle glucose utilization and mitochondrial oxidative metabolism-mediated upregulation of pyruvate dehydrogenase complex.

Celastrol, a natural triterpene from the Tripterygium wilfordii has been demonstrated to possess attributive properties to attenuate various animal models of obesity-associated conditions. The present study aimed to elucidate the putative targets of celastrol on intracellular glucose utilization and mitochondrial oxidative metabolism in the isolated quadriceps skeletal muscle of high-fat diet (HFD)-induced obese male C57BL6/J mice. Here we showed that celastrol remarkably attenuated obesity and insulin resistance through improvement of systemic glucose tolerance and insulin sensitivity. Enhanced mRNA transcription factors of key rate-limiting glycolytic and TCA cycle enzymes were observed following celastrol administration. The metabolic profiling revealed profound changes induced by celastrol administration on several key metabolites of glycolysis and tricarboxylic acid (TCA) cycle including glucose-1-phosphate, pyruvate, citrate, α-ketoglutarate, succinate and fumarate. Celastrol effectively increased mitochondrial oxidative functions via increased pyruvate dehydrogenase complex (PDC) activity and downregulated pyruvate dehydrogenase kinase 4 (PDK4) expressions. Enhanced succinate dehydrogenase (SDH) activity was noticed following celastrol co-supplementation, leading to a steady establishment of the electrochemical gradient across mitochondrial membrane for ATP production and mitochondrial biogenesis. In conclusion, the current findings accentuate the therapeutic potential of celastrol against HFD-induced obese mice via enhanced glucose utilization and mitochondrial oxidative metabolism-mediated upregulation of PDC activity in the skeletal muscle.

Celastrol attenuates high-fructose diet-induced inflammation and insulin resistance via inhibition of 11ß-hydroxysteroid dehydrogenase type 1 activity in rat adipose tissues.

High fructose consumption has been linked to low-grade inflammation and insulin resistance that results in increased intracellular 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) activity. Celastrol, a pentacyclic triterpene, has been demonstrated to exhibit multifaceted targets to attenuate various metabolic diseases associated with inflammation. However, the underlying mechanisms by which celastrol exerts its attributive properties on high fructose diet (HFrD)-induced metabolic syndrome remain elusive. Herein, the present study was aimed to elucidate the mechanistic targets of celastrol co-administrations upon HFrD in rats and evaluate its potential to modulate 11ß-HSD1 activity. Celastrol remarkably improved glucose tolerance, lipid profiles, and insulin sensitivity along with suppression of hepatic glucose production. In rat adipose tissues, celastrol attenuated nuclear factor-kappa B (NF-κB)-driven inflammation, reduced c-Jun N-terminal kinases (JNK) phosphorylation, and mitigated oxidative stress via upregulated genes expression involved in mitochondrial biogenesis. Furthermore, insulin signaling pathways were significantly improved through the restoration of Akt phosphorylation levels at Ser473 and Thr308 residues. Celastrol exhibited a potent, selective and specific inhibitor of intracellular 11ß-HSD1 towards oxidoreductase activity (IC50 value = 4.3 nM) in comparison to other HSD-related enzymes. Inhibition of 11ß-HSD1 expression in rat adipose microsomes reduced the availability of its cofactor NADPH and substrate H6PDH in couple to upregulated mRNA and protein expressions of glucocorticoid receptor. In conclusion, our results underscore the most likely conceivable mechanisms exhibited by celastrol against HFrD-induced metabolic dysregulations mainly through attenuating inflammation and insulin resistance, at least via specific inhibitions on 11ß-HSD1 activity in adipose tissues.