Antiproliferative activity of bicyclic benzimidazole nucleosides: synthesis, DNA-binding and cell cycle analysis

An efficient route was developed for synthesis of bicyclic benzimidazole nucleosides 1-4 from readily available D-glucose. The key reactions were Vorbruggen glycosylation and ring closing metathesis (RCM). Primarily, to understand the mode of DNA binding, we performed a molecular docking study and the binding was found to be in the minor groove region. Based on the proposed binding model, UV-visible and fluorescence spectroscopic techniques using calf thymus DNA (CT-DNA) demonstrated a non-inter-calative mode of binding. Antiproliferative activity of nucleosides 1-4 was tested against MCF-7 and MDA-MB-231 breast cancer cell lines and found to be active at low micromolar concentrations. Compounds 2 and 4 displayed significant antiproliferative activity as compared to 1 and 3 with the reference anticancer drug, doxorubicin. Cell cycle analysis showed that nucleoside 4 induced cell cycle arrest at the S-phase. Confocal microscopy has been performed to validate the induction of cellular apoptosis. Based on these findings, such modified bicyclic benzimidazole nucleosides will make a significant contribution to the development of anticancer drugs.