Synthesis and Characterization of Sulfonamide-Schiff Bases, and Investigation of Cytotoxic, Antioxidant, HDAC, and Apoptotic Activities in Human Colon Cancer Cells (DLD-1 and HT-29).

Comprehending the intricate mechanisms of apoptosis and its interaction with cytotoxic, antioxidant, and HDAC activities is imperative for devising effective cancer therapies. Sulfonamides and Schiff bases are compounds of pharmacological importance with known anticancer activity. Our study aimed to investigate the cytotoxic, antioxidant, HDAC, and apoptotic activities of new sulfonamide-Schiff bases in human colon cancer cells (DLD-1 and HT-29). New sulfonamide-derived Schiff base compounds (3a-d) were synthesized from the condensation of sulfamethoxypyridazine (1) and various aromatic aldehydes, and were characterized by FTIR, NMR (1H and 13C/APT), UV-Vis., and mass spectroscopy. Sulfonamide-derived Schiff bases 3a-d and compound 1 exhibited significant anticancer activity against colorectal cancer cell lines (DLD-1, HT-29). In the MTT assay, 3c was most active in DLD-1 (viability: 37.7%, IC₅₀ = 3.94 µM) and 3b in HT-29 (viability: 46.6%, IC₅₀ = 3.26 µM). In the WST-8 assay, 3c was strongest in DLD-1 (viability: 45.9%, IC₅₀ = 17.95 µM). None of the compounds showed toxicity in normal colon cells (CCD-18Co). qRT-PCR revealed upregulation of apoptotic (BAX, p53, Caspase-3/8/9) and antioxidant (SOD-1/2, CAT, GSS) genes, notably by 3a in DLD-1 and 3d in HT-29, while 3c reduced BCL-2 in HT-29 cells. ELISA confirmed strong antioxidant induction (3a: 70% in DLD-1) and HDAC inhibition (3d: 69% in HT-29). Western blot showed 3a increased p38/MAPK expression sevenfold in DLD-1 and fourfold in HT-29, while decreasing ERK1. Overall, 3c and 3d emerged as the most promising candidates, combining cytotoxic, antioxidant, HDAC inhibitory, and apoptotic effects, and may act as selective therapeutic agents by targeting the p38/MAPK-ERK1 pathway in colorectal cancer.