Synthesis, characterization, DNA binding, photo-induced DNA cleavage, and antimicrobial activity of metal complexes of a Schiff base derived from bis(3-aminophenyl)malonamide

A study of structure-activity relationship and anion-controlled quinolinyl Ag(I) complexes as antimicrobial and antioxidant agents as well as their interaction with macromolecules

In this communication, we feature the synthesis and in-depth characterization of a series of silver(I) complexes obtained from the complexation of quinolin-4-yl Schiff base ligands ((E)-2-((quinolin-4-ylmethylene)amino)phenol L_a, 2-(quinolin-4-yl)benzo[d]thiazole L_b, (E)-N-(2-fluorophenyl)-1-(quinolin-4-yl)methanimine L_c, (E)-N-(4-chlorophenyl)-1-(quinolin-4-yl)methanimine L_d, (E)-1-(quinolin-4-yl)-N-(p-tolyl)methanimine L_e, (E)-1-(quinolin-4-yl)-N-(thiophen-2-ylmethyl)methanimine L_f) and three different silver(I) anions (nitrate, perchlorate and triflate). Structurally, the complexes adopted different coordination geometries, which included distorted linear or distorted tetrahedral geometry. The complexes were evaluated in vitro for their potential antibacterial and antioxidant activities. In addition, their interactions with calf thymus-DNA (CT-DNA) and bovine serum albumin (BSA) were evaluated. All the complexes had a wide spectrum of effective antibacterial activity against gram-positive and gram-negative bacterial and good antioxidant properties. The interactions of the complexes with CT-DNA and BSA were observed to occur either through intercalation or through a minor groove binder, while the interaction of the complexes with BSA reveals that some of the complexes can strongly quench the fluorescence of BSA through the static mechanism. The molecular docking studies of the complexes were also done to further elucidate the modes of interaction with CT-DNA and BSA.

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 AgNO₃, AgClO₄ and AgCF₃SO₃. Q1-Q15 were characterized by various spectroscopic techniques and the structures of [Ag(L1)₂]NO₃Q1, [Ag(L1)₂]ClO₄Q6, [Ag(L2)₂]ClO₄Q7, [Ag(L2)₂]CF₃SO₃Q12 and [Ag(L4)₂]CF₃SO₃Q14 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]ClO₄Q7 with a benzothiazole moiety and [Ag(L4)₂]ClO₄Q9 with a methyl substituent had excellent cytotoxicity against HELA cells.

Evaluation of substituent bioactivity and anion impact of linear and T-shaped silver(i) pyridinyl complexes as potential antiproliferative, antioxidant, antimicrobial agents and DNA- and BSA-binders

The impact of ligand substituents and anion variation on the bio-activity of pyridinyl Ag(I) complexes was evaluated. The complexes showed potential therapeutic ability with notable anticancer, antioxidant, and antimicrobial activities.

Aryl variation and anion effect on CT-DNA binding and in vitro biological studies of pyridinyl Ag(I) complexes

Synthesis and spectroscopic characterization of five ligands ((E)-2-((pyridin-2-ylmethylene)amino)phenol L1, 2-(pyridin-2-yl)benzo[d]thiazole L2, (E)-N-(2-fluorophenyl)-1-(pyridin-2-yl)methanimine L3, (E)-1-(pyridin-2-yl)-N-(p-tolyl)methanimine L4 and (E)-1-(pyridin-2-yl)-N-(thiophen-2-ylmethyl)methanimine L5 along with fifteen silver(I) complexes of L1 - L5, with a general formula [AgL₂]⁺X^- (L = Schiff base and X = NO₃^-, ClO₄^- or CF₃SO₃^-) is reported. The structures of complexes [Ag(L4)₂]NO₃, [Ag(L5)₂]NO₃, [Ag(L3)₂]ClO₄, [Ag(L4)₂]ClO₄ and [Ag(L5)₂]CF₃SO₃ were determined unequivocally by single crystal X-ray diffraction analysis. Calf-thymus deoxyribonucleic acid (CT-DNA), bovine serum albumin (BSA) binding studies, antioxidant, and antibacterial studies were performed for all complexes. Complexes [Ag(L2)₂]NO₃, [Ag(L5)₂]NO₃, [Ag(L1)₂]ClO₄ and [Ag(L3)₂]ClO₄ whose ligands have an OH^- and F^- as substituents or with a thiophene or thiazole moiety showed better antibacterial activities with lower minimum inhibitory concentration (MIC) values compared to the standard ciprofloxacin, against most of the bacterial strains tested. Similarly, complexes [Ag(L1)₂]NO_3,[Ag(L2)₂]NO_3,[Ag(L3)₂]NO₃ and [Ag(L5)₂]NO₃ with the NO₃^- anion, [Ag(L1)₂]ClO₄ and [Ag(L2)₂]ClO₄ with ClO₄^- anion, and [Ag(L5)₂]CF₃SO₃ with CF₃SO₃^- anion showed higher activities for antioxidant studies. Complexes [Ag(L4)₂]ClO₄ and [Ag(L4)₂]CF₃SO₃ with the Methyl substituent and CF₃SO₃^- as the anion, displayed high antioxidant activities in FRAP (ferric reducing antioxidant power) than the standard ascorbic acid. Spectroscopic studies of all the complexes revealed their moderate to high interaction with calf thymus DNA via an intercalation mode. In addition, the relatively moderate interaction of most of the complexes with BSA was through a static quenching mechanism.