In this paper we present the formation of mono- and binuclear complexes by the octapeptide (c(HKHPHKHP)) with copper(II) ions. The ligand was synthesized manually by the solid-phase method. Its characteristic cyclic structure significantly influences the coordination abilities. The studied peptide has two Pro amino acid residues in the sequence. This causes the formation of two independent centres able to undertake metal ion binding. The potentiometric and spectroscopic (UV-vis, CD and EPR) studies were carried out in aqueous solutions in the pH range 2.5-11.0 at 298 K, HNO(3) was used as the solvent with KNO(3), where the ionic strength was 0.1 M. The analysis of the potentiometric together with spectroscopic studies have shown that the investigated peptide forms only mono-nuclear complexes when the metal-to-ligand molar ratio is 1 : 1. When the concentration of Cu(ii) ions increases and the ligand-to-metal molar ratio is 1 : 2 the formation of binuclear complexes is preferred in the system.

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The imidazole ring of histidine (His) and the methylcarboxylate function of aspartic acid (Asp) are crucial for crucial for catalysis, but also acts as inhibitor anion according to cyclic voltammetry observations. The system is highly tolerant to the presence of chloride, which is a feature of practical importance in efficient water oxidation catalysis.

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Regarding that the chronic use of commonly available non-steroidal and anti-inflammatory drugs (NSAIDs) is often restricted by their adverse effects, there is still a current need to search for and develop new, safe and effective anti-inflammatory agents. As a continuation of our previous work, we designed and synthesized a series of 18 novel N-substituted-1,2,4-triazole-based derivatives of pyrrolo[3,4-d]pyridazinone 4a-c-9a-c. The target compounds were afforded via a convenient way of synthesis, with good yields. The executed cell viability assay revealed that molecules 4a-7a, 9a, 4b-7b, 4c-7c do not exert a cytotoxic effect and were qualified for further investigations. According to the performed in vitro test, compounds 4a-7a, 9a, 4b, 7b, 4c show significant cyclooxygenase-2 (COX-2) inhibitory activity and a promising COX-2/COX-1 selectivity ratio. These findings are supported by a molecular docking study which demonstrates that new derivatives take position in the active site of COX-2 very similar to Meloxicam. Moreover, in the carried out in vitro evaluation within cells, the title molecules increase the viability of cells pre-incubated with the pro-inflammatory lipopolysaccharide and reduce the level of reactive oxygen and nitrogen species (RONS) in induced oxidative stress. The spectroscopic and molecular modeling study discloses that new compounds bind favorably to site II(m) of bovine serum albumin. Finally, we have also performed some in silico pharmacokinetic and drug-likeness predictions. Taking all of the results into consideration, the molecules belonging to series a (4a-7a, 9a) show the most promising biological profile.