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

Adesola A Adeleke,Veronica F Salau,Chunderika Mocktar,Bernard Omondi,Md Shahidul Islam,Sizwe J Zamisa,Kolawole Olofinsan

doi:10.3390/molecules26051205

Adesola A Adeleke, Veronica F Salau + Show 5 more

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https://doi.org/10.3390/molecules26051205

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Abstract

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 AgNO3, AgClO4 and AgCF3SO3. Q1–Q15 were characterized by various spectroscopic techniques and the structures of [Ag(L1)2]NO3 Q1, [Ag(L1)2]ClO4 Q6, [Ag(L2)2]ClO4 Q7, [Ag(L2)2]CF3SO3 Q12 and [Ag(L4)2]CF3SO3 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 IC50 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]ClO4 Q7 with a benzothiazole moiety and [Ag(L4)2]ClO4 Q9 with a methyl substituent had excellent cytotoxicity against HELA cells.

Highlights

Schiff bases are an extensively studied important class of ligands
The ligands were prepared by the condensation reaction of 2-quinolinecarboxaldehyde with five substituted aromatic anilines (2-fluoroaniline, L1; 2-aminobenzenethiol, L2; 4chloroaniline, L3; p-toluidine, L4; and 2-thiophenemethylamine, L5) in anhydrous ethanol in excellent yields as per the method in literature [30]
The air-stable solids are soluble in common organic solvents such as dichloromethane, acetonitrile, tetrahydrofuran, dimethylsulfoxide, dimethylformamide, and some in water

Summary

Introduction

Schiff bases are an extensively studied important class of ligands. Quinolines are derivatives of pyridine and are found in many biologically active natural [5,6] and synthetic [7,8,9] compounds Their Schiff base derivatives have been identified with various pharmaceutical activities [10,11]. Some free Schiff base ligands are known to be bioactive, literature has shown that incorporating metal in such ligands enhances their activities [12,13]. This has lately driven research in metal-based drugs. Our interest in silver(I) ion is due to its low toxicity to human at low concentration [19], high cytotoxicity [20], and good potency compared to other bioactive metal complexes such as cisplatin, known to have drawbacks which include nephrotoxicity, drug resistance, and cervical renal problems [21]

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