A binuclear zinc(II) Schiff base complex: Crystal structure characterization, antitumor activity and cell apoptosis induction in BEL-7404 tumor cells

Abstract

The Schiff base ligand, 4-chloro-2-(quinolin-8-yliminomethyl)-phenol (HClQP), reacts with ZnCl₂.4H₂O to afford a binuclear zinc(II) complex (<b style="mso-bidi-font-weight:normal">1</b>), which has been synthesized and characterized by IR, ESI-MS, elemental analysis and single crystal X-ray diffraction analysis. In complex (<b style="mso-bidi-font-weight: normal">1)</b>, the two zinc atoms are in a five-coordinated tetragonal pyramidal geometry and a four-coordinated tetrahedral geometry, respectively. The <i style="mso-bidi-font-style:normal">in vitro</i> cytotoxicities of complex (<b style="mso-bidi-font-weight:normal">1)</b> against four human tumor cell lines and the HL-7702 normal liver cell line have been screened and evaluated by MTT assay, in comparison with HClQP and cisplatin. The IC₅₀ values of complex (<b style="mso-bidi-font-weight: normal">1)</b> is in the range of 7.51–15.66 µ<i style="mso-bidi-font-style: normal">M</i> against these tumor cell lines, in which the MCF-7 and BEL-7404 cells showed the highest sensitivity to complex (<b style="mso-bidi-font-weight:normal">1)</b>. The HL-7702 cell line was neither sensitive to complex (<b style="mso-bidi-font-weight: normal">1)</b> nor to HClQP and cisplatin. This suggests the potent cytotoxic selectivity of complex (<b style="mso-bidi-font-weight:normal">1)</b> on the tumor cell lines. The cell apoptosis induction of complex (<b style="mso-bidi-font-weight: normal">1)</b> visualized by fluorescence microscopy shows evident apoptosis in BEL-7404 tumor cells induced by complex (<b style="mso-bidi-font-weight: normal">1)</b>. In view of these results, the central zinc(II) of complex (<b style="mso-bidi-font-weight:normal">1)</b> is expected to play a key role to exert the cell apoptosis induction in BEL-7404 cells, which may explain the significant antitumor activity of complex (<b style="mso-bidi-font-weight:normal">1)</b>.