Abstract Fifteen novel furoxan‐based nitric oxide (NO) releasing hybrids of estradiol derivatives were synthesized and evaluated in vitro anti‐proliferative activity in MDA‐MB‐231, A2780, Hela and HUVEC cell lines. Most of them displayed potent anti‐proliferative effects. Among the compounds, 4‐bromo‐3‐((phenylsulfonyl)‐1,2,5‐oxadiazole 2‐oxide)‐oxy‐propoxy‐estradiol (11 b) exhibited the best activity with IC50 values of 3.58–0.0008 μM. Preliminary pharmacological studies showed that 11 b induced apoptosis and hardly affected the cell cycle of MDA‐MB‐231 cell line. NO‐releasing capacity and inhibition of ERK/MAPK pathway signaling might explain the potent antineoplastic activity of these compounds. The preliminary structure‐activity relationship (SAR) showed that steroidal scaffolds with a linker in 3‐position were favorable moieties to evidently increase the bioactivities of these hybrids. Overall, these results implied that 11 b merited to be further investigated as a promising anti‐cancer candidate.
