New Mg(II) and Ca(II) Mixed Strontium Squarates: Structural Characterization, DNA/BSA Interaction, Antioxidant and Anticancer Activities

Abstract

New mixed alkaline earth metal squarates, viz [Sr0.965Mg0.035(C4O4)(H2O)2]·H2O—(1) and [Sr0.88Ca0.12(C4O4)(H2O)3]—(2) have been synthesized and characterized by single-crystal X-ray diffraction, thermal analysis, and biological studies, EB-CTDNA binding, BSA binding, antioxidant and cytotoxicity activity. The complexes 1 and 2 crystallized in triclinic and monoclinic space groups with eight and nine coordination number, respectively, from the reaction mixture of squaric acid and the respective metal nitrates in aqueous medium at pH 7. The complexes on thermal analysis show that they yield mixed metal carbonates at 544 °C as residue. Their interaction with EB-CTDNA evaluated by emission method substantiates the intercalative mode of binding. The protein binding (BSA) study by the fluorescence quenching method reveals that the complexes bind strongly with BSA. Antioxidant property analysis shows that they exhibit a strong radical scavenging ability against ABTS, DPPH and NO radicals. The in vitro cytotoxicity of the complexes examined for human breast cancer (MCF-7) and lung cancer (A549) cell lines exhibit substantial cytotoxic property. AO/EB and DAPI staining methods support that they induce apoptosis and nuclear fragmentations in MCF-7 and A549 cell lines.