One-pot synthesis of podophyllotoxin-thiourea congeners by employing NH₂SO₃H/NaI: Anticancer activity, DNA topoisomerase-II inhibition, and apoptosis inducing agents.

A facile one-pot method for the synthesis of novel podophyllotoxin-thiourea congeners has been developed by using NH2SO3H/NaI system. Interestingly, 4β-azido podophyllotoxin reduction with concomitant aryl isothiocyanates coupling under mild reaction conditions has been achieved. These compounds have been investigated for their in vitro cytotoxicity against A549, MDA MB-231, DU-145, LNCaP, and HGC-27 cancer cell lines. Some of the representative compounds have selectively exhibited cytotoxicity on DU-145 (human prostate cancer) cells and the most potent compound was 4a (IC50 of 0.50 ± 0.03 μM) with optimal safety therapeutic window (81.7 fold) on normal human prostate cell line (RWPE-1, IC50 of 40.85 ± 0.78). The flow-cytometric analysis of the compound 4a in prostate cancer cells indicated a strong G2/M-phase arrest and significant topoisomerase II inhibition activity. Furthermore, these compounds induce apoptosis as observed by Acridine Orange and Ethidium Bromide (AO/EB) staining and Annexin V binding assay. Molecular docking results of the title compounds with topoisomerase-IIα were presented as theoretical support for the experimental data.