Anticancer activity of four trinuclear cobalt complexes bearing bis(salicylidene)-1,3-propanediamine derivatives

Schiff base and its complexes are being paid more and more interests for their great prospects in biological applications. We reported here four cobalt(II) complexes [Co₃(L¹)₂(HCOO)₂] (1), [Co₃(L²)₂(HCOO)₂(CH₃OH)₂]·2CH₃OH (2), [Co₃(HL³)₂(OAc)₂(DMF)₂] (3) and [Co₃(HL⁴)₂(HCOO)₂(DMF)₂]·2H₂O (4) bearing the bis-Schiff base ligand of bis(5-bromosalicylidene)-1,3-propanediamine (H₂L¹), bis(5-bromosalicylidene)-2-methyl-1,3-propanediamine (H₂L²), bis(5-chlorosalicylidene)-2-hydroxyl-1,3-propanediamine (H₃L³) and bis(5-bromosalicylidene)-2-hydroxyl-1,3-propanediamine (H₃L⁴), respectively. The anti-tumor activities of the four titled complexes were screened on a series of tumor cell lines. After an overall consideration of their cytotoxicity on cancer cells and normal cells in comparison to those for cisplatin, complex 3 shows the best anticancer effect among the four titled complexes. It revealed the influence of anti-cancer effects of the substitution groups of H, Me and OH, as well as Cl and Br. Anticancer selectivity was also found for complex 3 on different cancer cell lines with the lowest IC₅₀ value on T-24 cells. Complex 3 induces cell apoptosis through mitochondrial pathway as demonstrated by increasing the level of reactive oxygen species, decreasing mitochondrial membrane potential, activating caspase 3/9 and arresting cell cycle in G1 phase.