A complex of Co(II) with 2-hydroxyphenyl-azo-2'-naphthol (HPAN) is far less cytotoxic than the parent compound on A549-lung carcinoma and peripheral blood mononuclear cells: Reasons for reduction in cytotoxicity.

Cytotoxic studies using an azo compound HPAN and its Co(II) complex were carried out on non-small lung epithelium carcinoma (A549) cells and peripheral blood mononuclear (PBM) cells. The results obtained suggest that the Co(II) complex is much less toxic toward both cell lines and the decreased toxicity due to the complex was more pronounced with carcinoma A549 cells. An attempt was made to correlate the findings related to cytotoxicity with the interaction of the compounds with DNA using calf thymus DNA as the target. The study was able to conclude that the complex was a relatively weak binder to calf thymus DNA. This information was used to explain the interaction of azo compounds with DNA in peripheral blood mononuclear cells and A549 lung carcinoma cells. It was concluded that the Co(II) complex interacts with DNA to a much lesser extent than HPAN alone. Cyclic voltammetry experiments carried out with HPAN and the Co(II) complex further showed that the presence of the metal ion in the complex prevents reduction of the azo group to such species that are responsible for inducing cytotoxicity. The overall finding was that complex formation with azo compounds might serve as a possible route to curb their toxicities.