Synthesis, DNA binding and cytotoxicity of new pyrazole emodin derivatives.

A series of new anthrapyrazoles were derived from emodin by attaching various cationic alkyl amino side chains onto a pyrazole ring which had been incorporated into the anthraquinone chromophore. Compared with emodin, the derivatives had significantly higher DNA binding affinity based on interaction with calf thymus DNA, and much more potent cytotoxicity against different tumor cells. The derivatives with a mono-cationic alkyl side chain exhibited the highest DNA binding affinity and cytotoxicity.