Microwave-assisted, catalyst and solvent free synthesis of tryptanthrin derivatives and their in-vitro cytotoxic activity on prostate DU145 cancer cell lines

A straightforward and efficient synthesis of tryptanthrin derivatives has been accomplished by the addition reaction of isatoic anhydrides and isatins under microwave irradiation. This decarboxylative and dehydrative addition reaction proceeded under solvent free conditions. In vitro cell based bioassay results revealed that 3ab and 3bb had unique cytotoxicity and selectivity with IC50 values of 5.90 �� 3.65 ��M and 1.96 �� 0.83 ��M, respectively in DU145 cells and they were found to be nontoxic to normal prostate epithelial RWPE-1 cells up to 25 ��M.