Quinolones are synthetic broad-spectrum antibiotics with good oral absorption and excellent bioavailability. Due to the chemical functions found on their nucleus (a carboxylic acid function at the 3-position, and in most cases a basic piperazinyl ring (or another N-heterocycle) at the 7-position, and a carbonyl oxygen atom at the 4-position) quinolones bind metal ions forming complexes in which they can act as bidentate, as unidentate and as bridging ligand, respectively. In the polymeric complexes in solid state, multiple modes of coordination are simultaneously possible. In strongly acidic conditions, quinolone molecules possessing a basic side nucleus are protonated and appear as cations in the ionic complexes. Interaction with metal ions has some important consequences for the solubility, pharmacokinetics and bioavailability of quinolones, and is also involved in the mechanism of action of these bactericidal agents. Many metal complexes with equal or enhanced antimicrobial activity compared to the parent quinolones were obtained. New strategies in the design of metal complexes of quinolones have led to compounds with anticancer activity. Analytical applications of complexation with metal ions were oriented toward two main directions: determination of quinolones based on complexation with metal ions or, reversely, determination of metal ions based on complexation with quinolones.

The widespread use of antibiotics has resulted in the emergence of drug-resistant populations of microorganisms. Clearly, one can see the need to develop new, more effective, antimicrobial agents that go beyond the explored ‘chemical space’. In this regard, their unique modes of action (e.g., reactive oxygen species (ROS) generation, redox activation, ligand exchange, depletion of substrates involved in vital cellular processes) render metal complexes as promising drug candidates. Several Ru(II/III) complexes have been included in, or are currently undergoing, clinical trials as anticancer agents. Based on the in-depth knowledge of their chemical properties and biological behavior, the interest in developing new ruthenium compounds as antibiotic, antifungal, antiparasitic, or antiviral drugs has risen. This review will discuss the advantages and disadvantages of Ru(II/III) frameworks as antimicrobial agents. Some aspects regarding the relationship between their chemical structure and mechanism of action, cellular localization, and/or metabolism of the ruthenium complexes in bacterial and eukaryotic cells are discussed as well. Regarding the antiviral activity, in light of current events related to the Covid-19 pandemic, the Ru(II/III) compounds used against SARS-CoV-2 (e.g., BOLD-100) are also reviewed herein.

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In the present investigation, new hydrazinecarbothioamides 4–6 were synthesized by reaction of 4-(4-X-phenylsulfonyl)benzoic acids hydrazides (X= H, Cl, Br) 1–3 with 2,4-difluorophenyl isothiocyanate and further these were treated with sodium hydroxide to obtain 1,2,4-triazole-3-thione derivatives 7–9. The reaction of 7–9 with α-halogenated ketones, in basic media, afforded new S-alkylated derivatives 10–15. The structures of the synthesized compounds have been established on the basis of 1H-NMR, 13C-NMR, IR, mass spectral studies and elemental analysis. The antioxidant activity of all compounds has been screened. Hydrazinecarbothioamides 4–6 showed excellent antioxidant activity and 1,2,4-triazole-3-thiones 7–9 showed good antioxidant activity using the DPPH method.

We report the synthesis and characterization of three new complexes of the natural flavonoid 5-hydroxyflavone (primuletin) and Al (III), Ga (III), In (III), respectively. The physico-chemical properties and structural features of these three novel compounds have been investigated by elemental and thermogravimetric analysis, molar conductance and several spectroscopic techniques, including FT-IR, UV-Vis and mass spectra. Based on the experimental data, the general chemical formula of the complexes iswhere M is the cation and n = 2 for Al (III), n = 0 for Ga (III), n = 1, for In (III); each one of the three 5-hydoxyflavone molecules acts as a monoanionic bidentate chelate ligand in the complexes. DFT calculations further sustain the proposed structures of the complexes. Cytotoxicity was studied using MTS assay on cervical, breast, colon and ovary adenocarcinoma cell lines.The central metal ions exert cytotoxic effects in a disparate manner: Al (III) enhances, while Ga (III) and In (III) decrease the cytotoxicity of the ligand.As a means to investigate the mechanism underlying the cytotoxic effects of the complexes, interactions with calf thymus DNA, human serum albumin and transferrin were also carried out.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.