Cations chelation and cytotoxicity of 8-hydroxyquinolone derivatives in water solutions

8-hydroxyquinolines (8HQ) derivatives have a wide range of activities, including antibacterial, antiviral, anticancer, antiparasitic and antifungal. They form complexes with divalent and trivalent metal cations. Low solubility of 8HQ in water limits their use. Absorbance spectra of aqueous solutions of 8HQ derivatives in the presence of Mg²⁺, Ca²⁺ and Zn²⁺, their stability over time, cytotoxicity and fluorescence in prostate and breast cancer cell lines were investigated. The 8HQ derivatives 2-(2-phenylethenyl)quinolin-8-ol (STQ-H) and 2-[2-(4-cyanophenyl)ethenyl]quinolin-8-ol (STQ-CN) were used. The cytotoxicity and fluorescence investigation was carried out on prostate DU-145 and breast MDA-MB-231 cancer cell lines. Changes of absorbance spectra of aqueous solutions of STQ-H and STQ-CN were revealed, which indicates the importance of the molar ratio of Mg²⁺, Ca²⁺, Zn²⁺ and chelator about 1:1. Absorbance of STQ-CN solution in a cations mixture was radically increased at equal molar proportions of each. Aqueous solutions of STQ-H were more stable than STQ-CN in the presence of Mg²⁺, Ca²⁺ and Zn²⁺ for 60 min. A high sensitivity of cells to STQ-CN was revealed. IC50 were 17.55 × 10⁻⁶ M for DU-145 and 1.96 × 10⁻⁶ M for MDA-MB-231. No cytotoxicity of STQ-H to DU-145 was detected, but it inhibited MDA-MB-231 (IC50 5.4 × 10⁻⁶ M). Fluorescence investigations were indicated a similar rate of both STQ-H and STQ-CN accumulation in the cytoplasm