4β-[4'-(1-(Aryl)ureido)benzamide]podophyllotoxins as DNA topoisomerase I and IIα inhibitors and apoptosis inducing agents.

A series of 4β-[4'-(1-(aryl)ureido)benzamide]podophyllotoxin congeners (11a-l) were synthesized and evaluated for their cytotoxic activity against six human cancer cell lines. Some of the compounds like 11a, 11h, 11k and 11l showed significant anti-proliferative activity in Colo-205 cells and were superior to etoposide. The flow-cytometric analysis studies indicated that these compounds show strong G1 cell cycle arrest, as well exhibited improved inhibitory activities on DNA topoisomerase I and IIα enzymes. These compounds induce apoptosis by up regulating caspase-3 protein as observed by ELISA and Western blotting analysis. In addition, a brief structure-activity relationship studies within the series along with docking results of representative compounds 11a, 11h, 11k, 11l were presented.