Heteroaromatic Pyrazole-Based Carbohydrazones: Structure-Dependent Redox Activity, DNA-Associated Spectroscopic Behavior, and Multifunctional Biological Properties

Abstract

Six novel pyrazole-based carbohydrazone derivatives (3a–3f) bearing structurally diverse heteroaromatic substituents were synthesized and characterized by ATR-FTIR, 1H NMR, APT-13C NMR, and HRMS analyses. Their multifunctional bioactivity was evaluated using antioxidant, photoprotective, CT-DNA-associated spectroscopic response, cytotoxicity, and scratch wound closure assays. Antioxidant activity was assessed by DPPH radical scavenging, Fe2+ chelation, and ferric thiocyanate (FTC) assays against appropriate reference standards, while photoprotective potential was determined by spectrophotometric SPF analysis using carrot seed oil as a reference. The benzothiazole-containing derivative (3f) showed the strongest DPPH scavenging activity, FTC antioxidant capacity, and photoprotective activity, while also producing one of the most pronounced CT-DNA-associated spectroscopic responses under the experimental conditions employed. In contrast, the benzimidazole derivative (3e) displayed the highest Fe2+ chelating activity among the synthesized compounds. In cell-based assays, the imidazole- and thiazole-containing derivatives (3b and 3c) showed the most favorable balance between growth-inhibitory potency and selectivity toward A431 epidermoid carcinoma cells relative to HaCaT keratinocytes. Scratch assay results did not support direct anti-migratory activity under the tested conditions but indicated compound-dependent modulation of wound-closure-associated cellular responses. Overall, these findings demonstrate that heteroaromatic substitution strongly modulates redox behavior, CT-DNA-associated spectroscopic behavior, photophysical properties, and cytotoxic selectivity in pyrazole-based carbohydrazones, identifying this scaffold as a structurally tunable platform for further bioactivity optimization.