**2.3 Cu(II) and Zn(II) complexes**

Hydroxyquinoline-thiosemicarbazones and its Cu(II) and Zn(II) complexes shows more cytotoxic activity towards human lung cell lines (A549) than their parent ligands [56]. Methyl pyruvate thiosemicarbazones and its Cu(II), Zn(II) complexes anti-proliferative activity studies reveals that copper complex was most effective on human leukemic cell line U937 than other compounds [57].
