Establishing the chromatographic fingerprints of flavan‐3‐ols and proanthocyanidins from rose hip (Rosa sp.) species

The profile of flavan‐3‐ols and proanthocyanidins in five different Rosa species (R. canina, R. glutinosa, R. rubiginosa, R. multiflora, and R. spinosissima) was estimated on high performance thin layer chromatography cellulose plates. Differences in flavanol and proanthocyanidin profiles of the extracts were evident, among which Rosa spinosissima stood out with catechin as the only detected flavanol and red zones as indication of anthocyanins. Furthermore, the elution solvent for thin layer chromatography with mass spectrometry analyses of glycosylated flavan‐3‐ols and proanthocyanidins was optimized, enabling identification of catechin, (epi)catechin hexoside, proanthocyanidin dimer, and proanthocyanidin dimers and trimers hexosides. A total of 15 flavanols and their derivatives were identified using ultra‐high‐performance liquid chromatography with linear trap quadrupole‐Orbitrap mass analyzer and epicatechin, gallocatechin, and proanthocyanidin trimer were identified only using this technique. However, proanthocyanidin trimer trihexoside was identified only by thin‐layer chromatography with mass spectrometry. To establish the relationships between the flavanols and proanthocyanidins composition of rose hip and their origin, principal component analysis was performed on the entire set of liquid chromatography/mass spectrometry data. Both principal components’ scores plots showed that Rosa spinosissima could be considered as an outlier. Our study demonstrated that flavanol and proanthocyanidin profiles of different rose hips depend on the geographical origin rather than on the cultivar and genotype.     

In situ photoreduction of Ag+-ions by TiO2 nanoparticles deposited on cotton and cotton/PET fabrics

The possibility of in situ photoreduction of Ag⁺-ions using TiO₂ nanoparticles deposited on cotton and cotton/PET fabrics in the presence of amino acid alanine and methyl alcohol has been discussed. The possible interaction between TiO₂, alanine and Ag⁺-ions was evaluated by FTIR analysis. The fabrication of TiO₂/Ag nanoparticles on both fabrics was confirmed by SEM, EDX, XRD, XPS and AAS analyses. Cotton and cotton/PET fabrics impregnated with TiO₂/Ag nanoparticles provided maximum reduction of Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus. Although excellent antibacterial activity was preserved after ten washing cycles, a significant amount of silver leached out from the fabrics into the washing bath. The perspiration fastness assessment revealed that smaller amounts of silver were also released from the fabrics into artificial sweat at pH 5.50 and 8.00. In addition, deposited TiO₂/Ag nanoparticles imparted maximum UV protection to fabrics.     

Estimation of single solute adsorption isotherms applying the nonlinear frequency response method using non-optimal frequencies

In order to estimate single solute adsorption isotherms, the nonlinear frequency response (FR) of a chromatographic column is analyzed experimentally and evaluated using the concept of higher order frequency response functions (FRFs) based on the Volterra series and generalized Fourier transform. In this case study, it has been investigated the adsorption of ethyl benzoate on octadecyl silica from a mixture of methanol and water (60:40) as a solvent. Experiments are performed using a standard gradient HPLC unit. For estimation of adsorption isotherms by the nonlinear FR method the column inlet concentration is changed in a nearly sine waveform around several steady-state concentrations. Using this method the first three local derivatives of a single solute adsorption isotherm are estimated from the low frequency asymptotes of the corresponding functions, i.e. the phase and first order derivative of the FRFs. For an accurate estimation of isotherm coefficients periodical experiments should be preformed for frequencies below a certain critical frequency. This is the frequency needed for approaching the low frequency asymptotic behaviour of the corresponding functions close enough, so that errors due to the non-feasibility of experiments with zero frequency can be neglected. Unfortunately, depending on the properties of the system, it can happen (as for the system investigated here) that experiments for the critical frequency would be too long and cannot be realized. In order to study the loss of accuracy of the nonlinear FR method, when it is applied for non-optimal frequencies, experiments are performed for frequencies approximately one order of magnitude higher than the critical frequency required to evaluate the FRF phases. The obtained isotherm model coefficients are compared with the ones estimated using conventional frontal analysis as a reference method. The isotherms determined by two methods are similar, however a closer look reveals that peaks predicted under overloading conditions differ.     

Kinetics and mechanism of the substitution reactions of some monofunctional Pt(II) complexes with heterocyclic nitrogen donor molecules. Crystal structure of [Pt(bpma)(pzBr)]Cl2·2H2O

Substitution reactions of [Pt(terpy)Cl]⁺ (terpy = 2,2′;6′,2′′-terpyridine), [Pt(bpma)Cl]⁺ (bpma = bis(2-pyridylmethyl)amine), [Pt(dien)Cl]⁺ (dien = diethylenetriamine or 1,5-diamino-3-azapentane) and [Pt(tpdm)Cl]⁺ (tpdm = tripyridinedimethane) with nitrogen donor heterocyclic molecules, such as 3-amino-4-iodo-pyrazole (pzI), 5-amino-4-bromo-3-methyl-pyrazole (pzBr) and imidazole (Im), were studied in aqueous 0.10 M NaClO₄ in the presence of 10 mM NaCl using variable-temperature UV–vis spectrophotometry. The second-order rate constants k₂ indicate decrease in reactivity in the order [Pt(terpy)Cl]⁺ > [Pt(bpma)Cl]⁺ > [Pt(tpdm)Cl]⁺ > [Pt(dien)Cl]⁺. The most reactive nucleophile among the heterocyclic compounds is imidazole, while pzI shows slightly higher reactivity than pzBr. Activation parameters were also determined and the negative values for entropies of activation, ΔS^≠, support an associative mode of substitution for all substitution processes. Crystal structure of [Pt(bpma)(pzBr)]Cl₂·2H₂O was determined by single-crystal X-ray analysis. The coordination geometry of the complex is distorted square-planar while the bond distance Pt–N2(pzBr) is longer than the other three Pt–N distances.     

Synergistic Heterobimetallic Manifold for Expedient Manganese(I)‐Catalyzed C−H Cyanation

The manganese‐catalyzed cyanation of inert C?H bonds was achieved within a heterobimetallic catalysis regime. The manganese(I) catalysis proved widely applicable and enabled C?H cyanations on indoles, pyrroles and thiophenes by facile C?H manganesation. The robustness of the manganese catalyst set the stage for the racemization‐free C?H cyanation of amino acids with excellent levels of positional and chemo selectivity by the new cyanating agent NCFS. Experimental and computational mechanistic studies provided strong support for a synergistic heterobimetallic activation mode, facilitating the key C?C formation.     

Gas phase noncovalent protein complexes that retain solution binding properties: Binding of xylobiose inhibitors to the β-1, 4 exoglucanase from <Emphasis Type="Italic">Cellulomonas fimi</Emphasis>

Tandem mass spectrometry has been used to compare gas-phase and solution binding of three small-molecule inhibitors to the wild type and three mutant forms of the catalytic domain of Cex, an enzyme that hydrolyses xylan and xylo-oligosaccharides. The inhibitors, xylobiosyl-deoxynojirimycin, xylobiosyl-isofagomine lactam, and xylobiosyl-isofagomine consist of a common distal xylose linked to different proximal aza-sugars. The three mutant forms of the enzyme contain the substitutions Asn44Ala, Gln87Met, and Gln87Tyr that alter the binding interactions between Cex and the distal sugar of each inhibitor. An electrospray ionization (ESI) triple quadrupole MS/MS system is used to measure the internal energies, DeltaE(int), that must be added to gas-phase ions to cause dissociation of the noncovalent enzyme-inhibitor complexes. Collision cross sections of ions of the apo-enzyme and enzyme-inhibitor complexes, which are required for the calculations of DeltaE(int), have also been measured. The results show that, in the gas phase, enzyme-inhibitor complexes have more compact, folded conformations than the corresponding apo-enzyme ions. With the mutant enzymes, the effects of substituting a single residue can be detected. The energies required to dissociate the gas-phase complexes follow the same trend as the values of DeltaG0 for dissociation of the complexes in solution. This trend is observed both with different inhibitors, which probe binding to the proximal sugar, and with mutants of Cex, which probe binding to the distal sugar. Thus the gas-phase complexes appear to retain much of their solution binding characteristics.     

Crystal Structures of AlCr2 and MoSi2: Same Structure Type vs. Different Bonding Pattern

In a joint effort utilizing modified sample preparation, microscopy, X-ray diffraction and micro-fabrication, it became possible to prepare single crystals of the “hidden” phase AlCr₂. High-resolution X-ray diffraction analysis is described in detail for two crystals with the similar overall composition, but different degree of disorder, which seems to be the main cause for the differing unit cell parameters. Chemical bonding analysis of AlCr₂ in comparison to prototypical MoSi₂ shows pronounced differences reflecting the interchange of main group element vs. transition metal as majority component.     

Synthesis,characterization and antimicrobial activity of β-aminovinylphosphonium salts derived from aromatic amino acids

This study presents the synthesis, characterization and antimicrobial activity evaluation of β-aminovinyl-phosphonium salts derived from aromatic amino acids. The compounds were prepared in the reaction of (formylmethyl)triphenylphosphonium chloride with various aromatic amino acids and their structures were determined by elemental analysis, IR and NMR spectroscopy. All synthesized compounds were tested for their antibacterial and antifungal activity.     

The protective role of melatonin under heavy metal-induced stress in Melissa Officinalis L.

Heavy metals, due to their inability to degrade, pose a serious environmental and nutritional problem. The accumulation of essential and non-essential heavy metals in living organisms reduces normal growth and development, resulting in acute poisoning, disease and even death of organisms. Melatonin is a very important multifunctional molecule in protecting plants from oxidative stress due to its ability to directly neutralize reactive oxygen species (ROS). Also, melatonin has a chelating property, which may contribute in reducing metal-induced toxicity. In this paper, the protective role of melatonin in counteracting metal-induced free radical generation was highlighted. Using the HPLC-FLD technique melatonin was identified and quantified in the roots and leaves of lemon balm ( Melissa officinalis L.), grown under photoperiod conditions. Furthermore, the response of plants pre-treated with exogenous 0.1 mM melatonin to the increased zinc (Zn) and cadmium (Cd) concentrations was observed, with changes in mineral (Ca, Mg), physiological and antioxidant status of the plant during heavy metals stress. The obtained melatonin concentrations were the highest published for dry plants so far. Elevated Cd and Zn levels in soil caused alternation in biochemical and physiological parameters of lemon balm leaves and roots. However, melatonin pre-treatment increased plant tolerance to heavy metals stress. Increased Cd and Zn uptake and their translocation into the leaves were also improved, indicating the possible use of melatonin in phytoremediation.