<span style="font-size:11.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;letter-spacing:-.1pt;mso-ansi-language:EN-GB;mso-fareast-language:EN-US; mso-bidi-language:HI" lang="EN-GB">Synthesis, antitumor activity and G-quadruplex DNA/ct-DNA binding property of a cationic platinum(II) complex of <span style="mso-bidi-font-weight: bold">2-(4-nitro)-imidazo-[5,6-<i style="mso-bidi-font-style:normal">f</i>][1,10]-phenanthroline</span></span>

Abstract

A cationic platinum(II) complex (<b style="mso-bidi-font-weight:normal">1</b>), [Pt(4-NOIP)(en)]∙Cl₂ (4-NOIP = 2-(4-nitro)-imidazo-[5,6-<i style="mso-bidi-font-style:normal">f</i>][1,10]-phenanthroline, en = 1,2-ethylenediamine), has been synthesized and characterized by IR, UV-vis, ESI-MS and element analysis. The interaction of complex (<b style="mso-bidi-font-weight:normal">1</b>) with ct-DNA and human telomeric G-quadruplex DNA [Htel-21] has been investigated by circular dichroism absorption and UV–vis absorption titration as well as fluorescent intercalator displacement assay. The circular dichroism absorption data shows that complex (<b style="mso-bidi-font-weight:normal">1</b>) can induce linear human telomeric DNA to transform into antiparallel G-quadruplex structure. The binding contants<i style="mso-bidi-font-style:normal"> </i>for complex (<b style="mso-bidi-font-weight: normal">1</b>) bound to Htel-21 and ct-DNA are 6.89×10⁵ and 7.53×10⁴ <i style="mso-bidi-font-style:normal">M</i><i style="mso-bidi-font-style:normal">^-</i>¹, respectively, indicating that complex (<b style="mso-bidi-font-weight:normal">1</b>) interacts with Htel-21 more intensively than ct-DNA. The FID assay suggests that complex (<b style="mso-bidi-font-weight:normal">1</b>) intercalates into ct-DNA and Htel-21 quite strongly. CD and UV–vis data together with FID experiments have shown that the complex can intercalate more intensely into Htel-21 and ct-DNA and induce formation and stabilization of antiparallel G-quadruplex. The anticancer activity of the complex have been tested against four different cancer cell lines and normal cell line HL-7702; the complex shows a higher activity than cisplatin and only weak cytotoxicity to HL-7702.