Synthesis, characterization, molecular docking and pharmacological evaluation of isoxazole derivatives as potent...

The present study is aimed to investigate the anti-inflammatory activities of thirteen substituted-isoxazole derivatives (5a-5m). Isoxazole is a key pharmacophore in medicinal chemistry, known for its broad range of pharmacological activities.This study explores the synthesis and anti-inflammatory potential of thirteen substituted-isoxazole derivatives (5a-5m), with 5c, 5d, 5e, and 5g being novel compounds.

The primary objectives were to synthesize some novel substituted isoxazole derivatives, evaluate their interaction with cyclooxygenase (COX-1/2) enzymes through computational methods, and assess their anti-inflammatory effectiveness in laboratory animals.

Substituted chalcones (0.01 mol) (2a-2m), sodium ethoxide (0.01 mol), and hydroxylamine hydrochloride (0.01 mol) were dissolved in absolute ethanol (15 ml), and then the mixture was refluxed for 6 h in an oil bath and monitored by TLC (ethyl acetate:hexane 7:3 v/v as eluent; a UV lamp was used to visualize the plates). After the completion of the reaction, as per TLC, the contents of the reaction mixture were poured into ice-cold water (50 ml). The obtained precipitates were filtered, washed two times, dried for 2 h at room temperature, and then recrystallized with ethenol. The structures of these compounds were confirmed via Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (¹H NMR) spectroscopy, carbon-13 nuclear magnetic resonance (¹³C NMR) spectroscopy, and mass spectrometry. Anti-inflammatory activity was evaluated using the carrageenan-induced rat paw edema method.

The results indicated that three compounds (5b, 5c, and 5d) demonstrated significant in vivo anti-inflammatory potential (% edema inhibition 75.68, 74.48, & 71.86 in 2 h and 76.71, 75.56, & 72.32 in 3 h) with modest effectiveness (0.83, 0.81 & 0.71), low toxicity, and minimal adverse effects. The molecular docking analyses further elucidated the interaction with the active site COX-2 enzyme (PDB ID: 4COX) using Autodock Vina. The compounds 5b, 5c, and 5d -8.7, -8.5, and -8.4 indicate good binding affinity (kcal/mol) and H-bond interaction with residues such as Cys41, Ala151, and Arg120 for COX-2, which also carried out RMSD values of 2.174, 41.13, and 22.25, which are decisive for the reported anti-inflammatory activity of diverse compounds.

The findings indicate that isoxazole derivatives have modest antiinflammatory potential, with compounds (5b, 5c, and 5d) acting as lead molecules to be studied further for pain relief with fewer adverse effects.