Synthesis, Crystal Structure, Characterization, In Vitro and In Silico Evaluation of Vanillin‐Pyrazole Heterocyclic Hybrids as Potent Antioxidants

Herein, we report the synthesis of a series of vanillin-pyrazole hybrids through a 1,3-dipolar cycloaddition reaction. The structures of these compounds were elucidated by various analytical methods, including NMR spectroscopy and HRMS, where compound 4a was further confirmed by x-ray diffraction. Their electronic properties were investigated through density function theory calculations at the B3LYP/6-311G(d,p). Moreover, the in vitro antioxidant activity of all compounds was evaluated by total antioxidant capacity and ferric reducing antioxidant power assays. As a result, compound 4a had the smallest HOMO-LUMO gap, indicating high electron-donating ability, while 4b showed the highest EHOMO (-5.688 eV), lowest hardness, and a narrow gap (∼4.20 eV). Additionally, compounds 4a-c, 6a, and 6b exhibited an important antioxidant activity with IC50 values ranging from 19.59 to 30.37 µM in the TAC method, compounds 4a and 6b showed remarkable activity of IC50 (92.13 and 102.64 µM, respectively) in the FRAP assay. Molecular docking and molecular dynamics simulations were performed to investigate the binding mode and behavior of 4a-c and 6b with human cytochrome P450 (CYP2C9) and human carbonyl reductase-1 (HCBR1), which were in good agreement with the observed antioxidant effects. These assessments revealed that vanillin-pyrazole hybrids could be used as promising derivatives in the quest for potent antioxidants. The ADMET properties indicated favorable drug-like properties for all compounds. Overall, compounds 4a, 4b, and 6b combine potent antioxidant activity with promising pharmacokinetic characteristics, highlighting vanillin-pyrazole hybrids as potential drug candidates for antioxidant therapy.