Synthesis and In Vitro Evaluation of Novel Thiazole-Hydrazone Derivatives with Antioxidant and Cytotoxic Potential

A new series of thiazole–hydrazone derivatives (2a–2l) was synthesized and evaluated for their in vitro antioxidant and cytotoxic properties. The structures of the synthesized compounds were confirmed by ¹H NMR, ¹³C NMR, and HRMS analyses. Antioxidant activity was assessed using the DPPH radical scavenging assay, while cytotoxicity was evaluated using the MTT assay in human colorectal cancer (HCT116) and non-small cell lung cancer (H460) cell lines. In the DPPH assay, compounds 2c and 2h exhibited the notable radical scavenging activity, with IC₅₀ values of 31.73 ± 0.004 μM and 31.13 ± 0.008 μM, respectively, comparable to the reference compound gallic acid (IC₅₀ = 29.48 ± 0.014 μM). Cytotoxicity screening performed at 100 μM for 24 h indicated that most derivatives did not significantly reduce cell viability in HCT116 cells. In contrast, a partial decrease in cell viability was observed in H460 cells for the selected compounds, with compound 2l showing a moderate effect (IC₅₀ = 82.00 ± 3.67 μM). The results indicate that the biological activity of these thiazole–hydrazone derivatives is strongly influenced by substitution patterns. While the compounds exhibited limited antiproliferative effects under the tested conditions, certain derivatives demonstrated notable antioxidant activity. These findings suggest that this scaffold may serve as a useful starting point for further structural optimization toward multifunctional bioactive molecules