Synthesis and Characterization of Substituted Isoxazolidines through 1,3-Dipolar Cycloaddition and Evaluation of their Antibacterial, Antioxidant and Molecular Docking Studies

Abstract

A series of substituted isoxazolidine derivatives (3a-g) was synthesized through a 1,3-dipolar [3+2] cycloaddition of a glutaraldehyde-derived nitrone with substituted cinnamaldehyde-derived chalcones. The synthesized derivatives were evaluated for their in vitro antibacterial activity against selected Gram-positive and Gram-negative bacterial strains using the disk diffusion method and for DPPH radical-scavenging activity. All compounds exhibited measurable antibacterial activity, with inhibition zones of 13-28 mm. Compound 3a gave the highest inhibition zones against E. coli (24 mm), K. oxytoca (20 mm), P. aeruginosa (28 mm) and S. epidermidis (21 mm). In the DPPH assay, the compounds displayed concentration-dependent radical-scavenging activity. Compound 3c showed the lowest reported IC50 value (47.8 µg/mL) followed by 3e (49.5 µg/mL) and 3b (50.6 µg/mL), while 3a showed 80.3% scavenging at 100 µg/mL. Molecular docking studies were performed against MRSA Sar2676 pantothenate synthetase, α-amylase and α-glucosidase. Compound 3a showed favourable predicted interactions with all three targets, with docking scores of -7.1, -8.4 and -7.8 kcal/mol, respectively.