Quinoline Functionalized Schiff Base Silver (I) Complexes: Interactions with Biomolecules and In Vitro Cytotoxicity, Antioxidant and Antimicrobial Activities

A series of fifteen silver (I) quinoline complexes Q1–Q15 have been synthesized and studied for their biological activities. Q1–Q15 were synthesized from the reactions of quinolinyl Schiff base derivatives L1–L5 (obtained by condensing 2-quinolinecarboxaldehyde with various aniline derivatives) with AgNO(3), AgClO(4) and AgCF(3)SO(3). Q1–Q15 were characterized by various spectroscopic techniques and the structures of [Ag(L1)(2)]NO(3) Q1, [Ag(L1)(2)]ClO(4) Q6, [Ag(L2)(2)]ClO(4) Q7, [Ag(L2)(2)]CF(3)SO(3) Q12 and [Ag(L4)(2)]CF(3)SO(3) Q14 were unequivocally determined by single crystal X-ray diffraction analysis. In vitro antimicrobial tests against Gram-positive and Gram-negative bacteria revealed the influence of structure and anion on the complexes′ moderate to excellent antibacterial activity. In vitro antioxidant activities of the complexes showed their good radical scavenging activity in ferric reducing antioxidant power (FRAP). Complexes with the fluorine substituent or the thiophene or benzothiazole moieties are more potent with IC(50) between 0.95 and 2.22 mg/mL than the standard used, ascorbic acid (2.68 mg/mL). The compounds showed a strong binding affinity with calf thymus-DNA via an intercalation mode and protein through a static quenching mechanism. Cytotoxicity activity was examined against three carcinoma cell lines (HELA, MDA-MB231, and SHSY5Y). [Ag(L2)(2)]ClO(4) Q7 with a benzothiazole moiety and [Ag(L4)(2)]ClO(4) Q9 with a methyl substituent had excellent cytotoxicity against HELA cells.