Design, synthesis and anticancer activity of naturally occurring C21-steroidal aglycone 3β-nitrogenous heterocyclic ester derivatives

•Two-step and highly efficient method to synthesize a series of novel C21-steroidal aglycone 3β-nitrogenous heterocyclic ester derivatives.•Most of synthetic derivatives showed moderate to significant cytotoxicities.•Compounds 1s and 2c exhibited the highest cytotoxicity with IC50 values ranging from 3.30 to 6.73 μM and from 3.07 to 6.37 μM, respectively.•Compound 2c induced HepG2 cells apoptosis and cell cycle arrest at S phase in a dose dependent manner. To investigate the effect of introduction of the nitrogenous heterocyclic ester group on the antitumor activities of naturally occurring C21-steroidal aglycone, a series of novel 3β-nitrogenous heterocyclic ester derivatives of caudatin, kidjoranin, qingyangshengenin, and rostratamin were synthesized. The results showed that most of synthetic derivatives showed moderate to significant cytotoxic activities against four human cancer cells (MCF-7, HCT-116, HeLa, and HepG2), in which compounds 1s and 2c with piperidine-4-acetyl substituent exhibited the highest cytotoxic activities against the four human cancer cells with IC50 values ranging from 3.30 to 6.73 μM and from 3.07 to 6.37 μM, respectively. Further antitumor mechanism studies displayed that compound 2c was effective in inducing apoptosis, arresting the cell cycle in the S phase in a dose- dependent manner in vitro. Overall, these present studies showed that introduction of nitrogenous heterocyclic ester group into C-3 position is one of effective strategy to improve anticancer activity for naturally occurring C21-steroidal aglycones deserved further investigation.