Synthesis, characterization and study of the catalytic properties of Zn(II) camphor derived complexes

Shedding Light on Metals Release from Chestnut Wood to Wine Spirit Using ICP-MS

Possible effects caused by mineral elements during wine spirit ageing are diverse. In this study, the evolution of the mineral composition of wine spirit during ageing with chestnut (Castanea sativa Mill.) wood was investigated. A wine distillate was aged in 250 L wooden barrels (traditional ageing) and in 50 L glass demijohns with wood staves and micro-oxygenation (alternative ageing). Sampling was performed after 21, 60, 180, 270, and 365 days of ageing. The elemental composition of the wine spirits, including alkaline, alkaline earth metals, and heavy metals, was assessed by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS). For most of the elements, no significant differences between wine spirits from distinct ageing modalities were observed. Ageing time had significant effect on most of them, with different trends and distinct magnitude of changes, depending on each specific element. The concentrations of the mineral elements found in the wine spirits were very low, especially those of heavy metals, which is quite positive in terms of quality and food safety. Novel information on metals released from chestnut wood to wine spirits confirms its appropriateness for ageing this beverage.

Synthesis and Characterization of Camphorimine Au(I) Complexes with a Remarkably High Antibacterial Activity towards B. contaminans and P. aeruginosa

Fourteen new camphorimine Au(I) complexes were synthesized and characterized by spectroscopic (NMR, FTIR) and elemental analysis. The structural arrangement of three selected examples were computed by Density Functional Theory (DFT) showing that the complexes essentially keep the {Au^I-CN} unit. The Minimum Inhibition Concentrations (MIC) were assessed for all complexes showing that they are active towards the Gram-negative strains E. coli ATCC25922, P. aeruginosa 477, and B. contaminans IST408 and the Gram-positive strain S. aureus Newman. The complexes display very high activity towards P. aeruginosa 477 and B. contaminans IST408 with selectivity towards B. contaminans. An inverse correlation between the MIC values and the gold content was found for B. contaminans and P. aeruginosa. However, plots of MIC values and Au content for P. aeruginosa 477 and B. contaminans IST408 follow distinct trends. No clear relationship could be established between the MIC values and the redox potentials of the complexes measured by cyclic voltammetry. The MIC values are essentially independent of the redox potentials either cathodic or anodic. The complexes K₃[{Au(CN)₂}₃(^A4L)] (8, Y = m-OHC₆H₄) and K₃[{Au(CN)₂}₃(^B2L)]·3H₂O (14, Z = p-C₆H₄) display the lower MIC values for the two strains. In normal fibroblast cells, the IC₅₀ values for the complexes are ca. one order of magnitude lower than their MIC values, although higher than that of the precursor KAu(CN)₂.

Ag(I) camphorimine complexes with antimicrobial activity towards clinically important bacteria and species of the Candida genus

The present work follows a previous report describing the antibacterial activity of silver camphorimine complexes of general formula [Ag(NO3)L]. The synthesis and demonstration of the antifungal and antibacterial activity of three novel [Ag(NO3)L] complexes (named 1, 2 and 3) is herein demonstrated. This work also shows for the first time that the previously studied complexes (named 4 to 8) also exert antifungal activity. The antibacterial activity of complexes was evaluated against Staphylococcus aureus, Pseudomonas aeruginosa, Burkholderia contaminans and Escherichia coli strains, while antifungal activity was tested against the Candida species C. albicans, C. glabrata, C. parapsilosis and C. tropicalis. The antimicrobial activity of the complexes ranged from very high (complex 4) to moderate (complex 6) or low (complex 8), depending on the structural and electronic characteristics of the camphorimine ligands. Notably, the highest antibacterial and anti-Candida activities do not coincide in the same complex and in some cases they were even opposite, as is the case of complex 4 which exhibits a high anti-bacterial and low antifungal activity. These distinct results suggest that the complexes may have different mechanisms against prokaryotic and eukaryotic cells. The antifungal activity of the Ag(I) camphorimine complexes (in particular of complex 1) was found to be very high (MIC = 2 μg/mL) against C. parapsilosis, being also registered a prominent activity against C. tropicalis and C. glabrata. None of the tested compounds inhibited C. albicans growth, being this attributed to the ability of these yeast cells to mediate the formation of less toxic Ag nanoparticles, as confirmed by Scanning Electron Microscopy images. The high antibacterial and anti-Candida activities of the here studied camphorimine complexes, especially of complexes 1 and 7, suggests a potential therapeutic application for these compounds.

Strecker degradation of amino acids promoted by a camphor-derived sulfonamide

A camphor-derived sulfonimine with a conjugated carbonyl group, oxoimine 1 (O₂SNC₁₀H₁₃O), reacts with amino acids (glycine, L-alanine, L-phenylalanine, L-leucine) to form a compound O₂SNC₁₀H₁₃NC₁₀H₁₄NSO₂ (2) which was characterized by spectroscopic means (MS and NMR) and supported by DFT calculations. The product, a single diastereoisomer, contains two oxoimine units connected by a –N= bridge, and thus has a structural analogy to the colored product Ruhemann´s purple obtained by the ninhydrin reaction with amino acids. A plausible reaction mechanism that involves zwitterions, a Strecker degradation of an intermediate imine and water-catalyzed tautomerizations was developed by means of DFT calculations on potential transition states.

Antibacterial activity of silver camphorimine coordination polymers

[Ag(NO₃)(OC₁₀H₁₄NC₆H₄NC₁₀H₁₄O)] is the first bi-camphor silver coordination polymer structurally characterized. It displays bactericidal activity against Gram-negative and Gram-positive strains comparable to drugs in use.

Oxygen activation by copper camphor complexes

In situreduction of CuCl₂enables formation of Cu(i) complexes prone to activate molecular oxygen from air towards catalytic oxidation of 1,3-dicarbonyls.