Evaluation of Cytotoxic, COX Inhibitory, and Antimicrobial Activities of Novel Isoxazole-carboxamide Derivatives

Isoxazole derivatives are one of the heterocyclic structures that have various biological activi-ties. Objective: This study aimed to design and synthesize novel isoxazole derivatives and evaluate their cyto-toxic, cyclooxygenase (COX) inhibitory, and antimicrobial activities. Methods: Coupling reactions of aniline derivatives and isoxazole carboxylic acid have been established to synthesize chloro-fluorophenyl-isoxazole carboxamide derivatives. The synthesized compounds were characterized using¹H,¹³C-NMR, IR, and HRMS spectrum analysis and evaluated by MTS, COX kit, and antimicrobial microdilution assays. Results: The synthesized compounds showed moderate to potent cytotoxic activity against all the screened cancer cell lines (except 2b against HepG2) with an IC₅₀ range of 0.107-77.83 µg/ml. The results showed that the most potent compound against cervical cancer cell line (HeLa) was the 2b com-pound, with an IC₅₀ value of 0.11±0.10 µg/ml, which is less than the IC₅₀ for the potent anticancer drug Doxorubicin. While the 2a and 2b compounds have potential antiproliferative activities against Hep3B with IC₅₀ doses of 2.774±0.53 and 3.621±1.56 µg/ml, respectively. Furthermore, 2c compound was the most active against MCF7, with an IC₅₀ value of 1.59±1.60 µg/ml. In addition, the most potent isoxazole derivative against the COX1 enzyme was the 2b compound, with an IC₅₀ value of 0.391 µg/ml, and compound 2a had a good selectivity ratio of 1.44 compared to the Ketoprofen positive control. However, compound 2c showed antifungal activity against Candida albicans with an MIC value of 2.0 mg/ml in comparison to the antifungal drug Fluconazole (MIC = 1.65 mg/ml). Conclusion: The synthesized compounds could be candidates for anticancer drugs in the future, and other analogues and cytotoxicity evaluations should be conducted.