Synthesis and biological evaluation of 4-aza-2,3-dihydropyridophenanthrolines as tubulin polymerization inhibitors.

A series of novel 4-aza-2,3-dihydropyridophenanthrolines 12(a-t) were synthesized by a one-step three component condensation of 1,10-phenanthroline amine, tetronic acid and various aromatic aldehydes. These were evaluated for their antiproliferative activity against three human cancer cell lines (MIAPACA, MCF-7 and HeLa) using SRB assay. Majority of the tested compounds exhibited significant anticancer activity on these cell lines and interestingly compounds 12h and 12i were more potent than etoposide and podophyllotoxin against all three tested cancer cell lines with GI50 values in the range of 0.01-0.5 μM. Furthermore, these compounds showed significant inhibition of tubulin polymerization which is comparable to that of podophyllotoxin and disrupted microtubule network by accumulating tubulin in the soluble fraction. The flow cytometry analysis confirmed that the synthesized compounds led to cell cycle arrest at the G2/M phase. Moreover, the structure activity relationship studies in this series are also discussed.