Synthesis, cytotoxicity, topoisomerase I inhibition and molecular docking of novel phosphoramide mustard sophoridinic acid analogues

A series of novel phosphoramide mustard sophoridinic acid analogues, consisting of nitrogen mustard group and sophoridinic acid scaffold, have been designed, synthesized and evaluated for their topoisomerase inhibitory activity as well as cytotoxicity against six tumor cell lines (SMMC-7721, LoVo, MCF-7, K562, S180 and H22) and a normal cell line (L929). Among the compounds tested, five were found to be potent inhibitors and exhibited potent cytotoxicity against S180 and H22 cell lines with IC50 values of 1–4 μM. Further mechanistic studies showed that this class of compounds acted as novel topoisomerase I (Topo I) catalytic inhibitors by preventing the binding of Topo I to DNA and inhibiting the cleavage of DNA, and molecular docking studies revealed that the binding energy for these compounds was comparable to that for classic Topo I inhibitors CPT and HCPT, indicating that the compounds have an interaction with DNA and Topo I.