Design, synthesis and biological evaluation of novel podophyllotoxin–melatonin heterodimers against ovarian cancer cell lines

Ovarian cancer remains the deadliest gynecological malignancy due to late diagnosis and the development of chemoresistance, highlighting the need for novel therapeutic agents. In this study, a series of podophyllotoxin–melatonin hybrids was synthesized using click chemistry to combine the anticancer properties of both pharmacophores. Structural modifications included variation of C-7 stereochemistry, melatonin attachment site, and linker length. The compounds were evaluated against ovarian cancer cell lines OVCAR-3, SKOV3, and MDAH 2774. Derivatives with the natural R configuration showed the highest activity, with compound 17a emerging as the most potent analog (IC₅₀ = 0.13–0.35 µM), exceeding the activity of etoposide and demonstrating favorable selectivity toward cancer cells. Mechanistic studies revealed that 17a induced G2/M cell cycle arrest and apoptosis in OVCAR-3 cells. Molecular docking and dynamics simulations confirmed binding within the colchicine-binding site in a mode similar to podophyllotoxin. Selected compounds ( 14a and 15a ) also exhibited good hemocompatibility and antioxidant properties, including protection against oxidative stress-induced hemolysis. Overall, these results highlight podophyllotoxin–melatonin hybrids as promising candidates for further development as anticancer agents. However, the findings are currently limited to in vitro and in silico studies, and the selectivity window toward normal cells requires further investigation. In particular, compound 17a emerges as a potent lead structure warranting advanced preclinical evaluation.