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

Abstract

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.