Abstract
Novel complexes of type [Cu(N-N)(dmtp)2(OH2)](ClO4)2·dmtp ((1) N-N: 2,2′-bipyridine; (2) L: 1,10-phenantroline and dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine) were designed in order to obtain biologically active compounds. Complexes were characterized as mononuclear species that crystallized in the space group P-1 of the triclinic system with a square pyramidal geometry around the copper (II). In addition to the antiproliferative effect on murine melanoma B16 cells, complex (1) exhibited low toxicity on normal BJ cells and did not affect membrane integrity. Complex (2) proved to be a more potent antimicrobial in comparison with (1), but both compounds were more active in comparison with dmtp—both against planktonic cells and biofilms. A stronger antimicrobial and antibiofilm effect was noticed against the Gram-positive strains, including methicillin-resistant Staphylococcus aureus (MRSA). Both electron paramagnetic resonance (EPR) and Saccharomyces cerevisiae studies indicated that the complexes were scavengers rather than reactive oxygen species promoters. Their DNA intercalating capacity was evidenced by modifications in both absorption and fluorescence spectra. Furthermore, both complexes exhibited nuclease-like activity, which increased in the presence of hydrogen peroxide.
Highlights
The triazolopyrimidine derivatives are valuable pharmacophores based on their resemblance to purine bases
A complex supramolecular network is generated through π-π stacking interactions realized between both 2,2 -bipyridine/1,10-phenanthroline belonging to different cationic units as well as between these and free triazolopyrimidine moieties
Complex (1) exhibits the ability to reduce the viability of B16 cells in a dosedependent manner and does not show any significant toxicity against BJ and Saccharomyces cerevisiae cells in the concentration ranges proven for the manifestation of biological activity
Summary
The triazolopyrimidine derivatives are valuable pharmacophores based on their resemblance to purine bases. Complexes with mixed ligands [Cu(N-N)2(pmtp)](ClO4) (N-N: 2,2 -bipyridine (bpy) and phen) showed antibacterial potential against several bacterial strains, including MRSA, the extended-spectrum beta-lactamase (ESBL)-producing E. coli 5, and the multi-drug-resistant P. aeruginosa 9027, both in planktonic and biofilm growth state [18]. Among these species, [Cu(pmtp)(CH3COO)2]0.5H2O and [Cu(pmtp)(OH2)3](ClO4)3H2O induce a decrease in the DNA content of cells in the G0/G1 phase in a human colon adenocarcinoma cell line (HT 29) [27], while [Cu(N-N)2(pmtp)](ClO4) exhibited excellent activity against B16 murine melanoma cells, that in addition, is accompanied by a lack of cytotoxicity against healthy BJ cells [18]. Similar interactions involving alternating π· · · π interactions between the phen ligands of two complex moieties (Cg1· · · Cg1 3.594 Å) and π· · · π interactions between a part of the phen and the five-member aromatic ring of the free dmtp (Cg2· · · Cg3 3.463 Å) can be noticed for complex (2) (Supplementary Figure S3, Supplementary Table S3)
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