Zinc(II) Complexes with Amino Acids for Potential Use in Dermatology: Synthesis, Crystal Structures, and Antibacterial Activity

Abstract

The multifunctional profile of Zn2+ has influenced its great popularity in various pharmaceutical, food, and cosmetic products. Despite the use of different inorganic and organic zinc derivatives, the search for new zinc-containing compounds with a safer skin profile still remains an open issue. The present paper describes the synthesis, structural characterization, and antibacterial activity of zinc(II) complexes with proteinogenic amino acids as potential candidates for dermatological treatments. The obtained complexes are of the general formula [Zn(AA)2], where AA represents an amino acid (L-Glu, Gly, L-His, L-Pro, L-Met, and L-Trp). Their synthesis was designed in such a way that the final bis(aminoacidate) zinc(II) complexes did not contain any counter-ions such as Cl−, NO3−, or SO42− that can cause some skin irritations. The chemical structure and composition of the compounds were identified by 1H NMR spectroscopy and elemental analysis, and four were also characterized by single-crystal X-ray diffraction. The Hirshfeld surface analysis for the Zn2+ metallic center helped to determine its coordination number and geometry for each complex. Finally, the antibacterial properties of the complexes were determined with respect to three Gram-positive strains, viz. Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228, and Streptococcus pyogenes ATCC 19615, and two Gram-negative bacteria, viz. Escherichia coli ATCC 25992 and Pseudomonas aeruginosa ATCC 27853, and were compared with the activity of zinc 2-pirrolidone 5-carboxylate (ZnPCA), commonly applied in dermatology. It was found that the Zn(II) complexes with methionine and glycine exhibited a higher antibacterial activity than the tested standard, and the antimicrobial properties of complex with Trp were satisfactory. The results of the antimicrobial activity examination allow us to postulate that the obtained zinc complexes might become new active substances for use in dermatological products.

On the Hirshfeld surface for copper(II) atoms in different coordination environments

“…Following the recent approach where the Hirshfeld surface is generated for the metal centre of transition metal compounds, here we investigate the behaviour of the Cu(II) Hirshfeld surfaces in different coordination environments and geometries. A similar investigation has been conducted recently on zinc(II) metal centres coordinated to amino acids in different geometries, achieving similar results (Abendrot et al, 2020), thus indicating the generality of this approach.…”

Equilibria in Aqueous Cobalt(II)—Reduced Schiff Base N-(2-hydroxybenzyl)alanine System: Chemical Characterization, Kinetic Analysis, Antimicrobial and Cytotoxic Properties

“…The reduced form of the Schiff base, derived from an amino acid and a carbonyl compound (e.g., salicylaldehyde), can form transition metal complexes with important applications [ 4 , 5 , 6 ]. Amino acids play important roles in various biochemical processes as endogenous ligands; in addition, their complexes with biologically-active metal ions have also proved to be useful antibacterial agents and metalloprotein models [ 7 , 8 , 9 ].…”

Transition Metal Complexes with Flufenamic Acid for Pharmaceutical Applications—A Novel Three-Centered Coordination Polymer of Mn(II) Flufenamate

“…The structural investigations of 1 have been augmented by the Hirshfeld Surface (HS) analysis (University of Western Australia, Crawley, Australia) of symmetrically independent metal centers Mn1, Mn2 and Mn3. This approach has been successfully applied for metal complexes by Pinto et al [ 41 ] and Abendrot et al [ 42 ]. As shown in the Figure 2 , HS of the central Mn1 is diverse than those generated for wing atoms Mn2 and Mn3.…”