Comparative cytotoxicity of tachpyr and its metal derivatives. Viability was assessed after 72 hours exposure to the indicated compounds as described in the Materials and Methods. (◍) tachpyr; (○) [Mg]tachpyr; (▾) [Mn]tachpyr; (▿) [Cu]tachpyr; (▩) [Zn]tachpyr; (□) [Ca]tachpyr.