The growing prevalence of Alzheimer's disease calls for a drug that can simultaneously act towards several targets involved in the pathophysiology of the disease. In our study, we evaluated the potential of hydrazone and N-acylhydrazone derivatives of vitamin B6 and pyridine-4-carbaldehyde to be used as multi-target directed ligands targeting cholinergic system by inhibiting acetyl- and butyrylcholinesterase, lowering the accumulation of β-amyloid plaques by inhibiting both the β-secretase activity and amyloid self-aggregation, and maintaining the biometal balance by chelating certain biometals. Our results showed that all of the tested hydrazones were potent inhibitors of human cholinesterases with inhibition constants (Ki) in micromolar range able to lower the activity of β-secretase, inhibit amyloid aggregation, chelate biometals and act as antioxidants. Also, most of them were estimated to be able to cross the blood-brain barrier by passive transport and to be absorbed in human intestines as well as with moderate metabolic stability in liver microsomes.

Two newly synthesized coumarin–palladium(II) complexes (C1 and C2) were characterized using elemental analysis, spectroscopy (IR and 1H-13C NMR), and DFT methods at the B3LYP-D3BJ/6-311+G(d,p) level of theory. The in vitro and in silico cytotoxicity of coumarin ligands and their corresponding Pd(II) complexes was examined. For in vitro testing, five cell lines were selected, namely human cervical adenocarcinoma (HeLa), the melanoma cell line (FemX), epithelial lung carcinoma (A549), the somatic umbilical vein endothelial cell line (EA.hi926), and pancreatic ductal adenocarcinoma (Panc-1). In order to examine the in silico inhibitory potential and estimate inhibitory constants and binding energies, molecular docking studies were performed. The inhibitory activity of C1 and C2 was investigated towards epidermal growth factor receptor (EGFR), receptor tyrosine kinase (RTK), and B-cell lymphoma 2 (BCL-2). According to the results obtained from the molecular docking simulations, the inhibitory activity of the investigated complexes towards all the investigated proteins is equivalent or superior in comparison with current therapeutical options. Moreover, because of the low binding energies and the high correlation rate with experimentally obtained results, it was shown that, out of the three, the inhibition of RTK is the most probable mechanism of the cytotoxic activity of the investigated compounds.

An unexpected tandem reaction consisting of amide coupling and hydroamination occurring with common triazole coupling reagents.

Two 4-hydroxycoumarin derivatives: (E)-3-(1-((4-hydroxy-3-methoxyphenyl)amino) -ethylidene) chromane-2,4-dione (L1) and (E)-3-(1-((3-hydroxy-4-methoxyphenyl)-amino)ethylidene) chromane-2,4-dione (L2), were prepared and structurally characterized by spectroscopic techniques in combination with the B3LYP-D3BJ theoretical method. The interactions between newly synthesized compounds and human serum albumin (HSA) were investigated under physiological conditions at 296,303, and 310 K by fluorescence and absorption spectroscopy, molecular docking, and molecular dynamic simulations. The results of absorption and fluorescence spectral analysis showed that ligands quenched HSA fluorescence through a static process. The corresponding thermodynamic parameters Delta H-0, Delta S-0, and Delta G(0) were calculated according to Van't Hoff's equation. The obtained results indicated that compounds bind spontaneously to HSA mainly by van der Waals's forces and through hydrogen bonds. Ligand-competitive displacement experiments, using known site-specific ligands for HSA's binding sites (I and II) suggest that ligands had a higher affinity for site I (subdomain IIA). The results of the computational analysis follow the experimental data, and the obtained results suggest that the investigated compounds show a good binding affinity according to the HSA receptor, which will be useful for future studies related to rational drug design. (C) 2022 Elsevier B.V. All rights reserved.

Seven pyridoxal dioxime quaternary salts (1–7) were synthesized with the aim of studying their interactions with human acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The synthesis was achieved by the quaternization of pyridoxal monooxime with substituted 2-bromoacetophenone oximes (phenacyl bromide oximes). All compounds, prepared in good yields (43–76%) and characterized by 1D and 2D NMR spectroscopy, were evaluated as reversible inhibitors of cholinesterase and/or reactivators of enzymes inhibited by toxic organophosphorus compounds. Their potency was compared with that of their monooxime analogues and medically approved oxime HI-6. The obtained pyridoxal dioximes were relatively weak inhibitors for both enzymes (Ki = 100–400 µM). The second oxime group in the structure did not improve the binding compared to the monooxime analogues. The same was observed for reactivation of VX-, tabun-, and paraoxon-inhibited AChE and BChE, where no significant efficiency burst was noted. In silico analysis and molecular docking studies connected the kinetic data to the structural features of the tested compound, showing that the low binding affinity and reactivation efficacy may be a consequence of a bulk structure hindering important reactive groups. The tested dioximes were non-toxic to human neuroblastoma cells (SH-SY5Y) and human embryonal kidney cells (HEK293).

p-Disubstituted phenyldiketopiperazines 1 (R = H), 2 (R = NO2) and 3 (R = -N(CH3)(2)) were synthesized and characterized by NMR in solution and IR spectroscopy. The identity of the compounds was confirmed and their fragmentation analyzed by ESI-MS and HRMS spectrometry. X-ray single crystal structures revealed that the three compounds crystallize in space groups P2(1) (1), Pbca (2) and P2(1)/c (3), respectively. The solid-state structures of 1-3 were further analyzed by a combination of solid-state NMR spectroscopy and GIPAW calculations. The NMR crystallography approach was used to analyze symmetry breaking of nearly centrosymmetric molecules in 1, and disorder of piperazine groups in crystal structure of 3. (C) 2021 Elsevier B.V. All rights reserved.

In the review of total phenolic contents (TPCs) of acacia, lime, and chestnut honey samples from several literature sources, large differences were noticed, which cannot be attributed only to seasonal or geographical variations. The dependence of TPC on the process of construction of the calibration line is illustrated in the measurement of acacia, lime, and chestnut honey types from Croatia and neighbouring countries (Serbia, Italy, and Hungary). TPCs are determined for 39 uni-floral honey samples by four calibration lines and four TPC values are obtained for each honey sample. Obtained results are compared mutually, as well as with the literature results for honey samples of the same type. For each honey type, the average of all determined TPCs determined in this study is in the middle of literature values. The average TPC values for chestnut honey samples were found to be 1.5 and 3 times higher than those for lime and acacia, respectively. The effects of two factors regularly considered in the determination of calibration lines are analyzed: (1) the concentration range of the standard chemical and (2) whether the calibration line is drawn through the origin, or not. The final results strongly depend on these two factors that should be considered in future TPC estimations.

The effect of different hydrodistillation pretreatments, namely, reflux extraction, reflux extraction with the addition of cell wall-degrading enzymes, and ultrasound, on the yield and chemical composition of essential oils of sage, bay laurel, and rosemary was examined. All pretreatments improved essential oil yield compared to no-pretreatment control (40–64% yield increase), while the oil quality remained mostly unchanged (as shown by statistical analysis of GC-MS results). However, enzyme-assisted reflux extraction pretreatment did not significantly outperform reflux extraction (no-enzyme control), suggesting that the observed yield increase was mostly a consequence of reflux extraction and enzymatic activity had only a minute effect. Thus, we show that ultrasound and reflux extraction pretreatments are beneficial in the production of essential oils of selected Mediterranean plants, but the application of enzymes has to be carefully re-evaluated.

Three novel structures of 9,10-anthracene amino acid conjugates have been determined by combination of single crystal and powder X-ray diffraction measurements, pseudopotential plane wave DFT optimizations and 13C solid state NMR spectroscopy, including GIPAW calculation of the NMR parameters. All three structures show anti-conformation of amino acid side chains attached to the anthracene unit. For compounds Ant–(CO–Phe-OMe)2, (1) and Ant–(CO–Gly-Phe-OMe)2 (2), anti-conformation is in accordance with nearly centrosymmetric crystallographic structures, while for Ant–(CO–Val-OMe)2 (3), anti-conformation is in accordance with approximate 2-fold molecular axis passing through the plane of anthracene unit. Centres of inversion in 1 and 2 are approximate due to the usage of optically pure amino acids. Rotation axis in 3 is approximate due to the displacement of molecules from crystallographic 2-fold axes present in tetragonal P41212 space group, resulting in a structure more accurate described in space group P212121.

Invertases are glycosidases applied for synthesis of alkyl glycosides that are important and effective surfactants. Stability of invertases in the environment with increased content of organic solvent is crucial for increase of productivity of glycosidases. Their stability is significantly influenced by N-glycosylation. However, yeast N-glycosylation pathways may synthesize plethora of N-glycan structures. A total natural crude mixture of invertase glycoforms (EINV) extracted from Saccharomyces cerevisiae was subfractionated by anion-exchange chromatography on industrial monolithic supports to obtain different glycoforms (EINV1-EINV3). Separated glycoforms exhibited different stabilities in water-alcohol solutions that are in direct correlation with the amount of phosphate bound to N-glycans. Observed differences in stability of different invertase glycoforms were used to improve productivity of methyl β-d-fructofuranoside (MF) synthesis. The efficiency and yield of MF synthesis were improved more than 50% when the most stabile glycoform bearing the lowest amount of phosphorylated N-glycans is selected and utilized. These data underline the importance of analysis of glycan structures attached to glycoproteins, demonstrate different impact of N-glycans on the surface charge and enzyme stability in regard to particular reaction environment, and provide a platform for improvement of yield of industrial enzymatic synthesis by chromatographic selection of glycoforms on monolithic supports.

Most organic solvents used in quaternization reactions are volatile, hazardous, toxic and form by-products, thus inducing health issues and pollution. Deep eutectic solvents are greener alternatives, but they have not been tested yet in the quaternization reaction. Here we propose eutectic solvents in the quaternization reaction of nicotinamide with substituted 2-bromoacetophenones. The reaction was performed at 80 °C by three synthetic approaches: conventional during 2–6 h, microwave during 20 min and ultrasonic during 3 h. The highest yields of about 98% were obtained by microwave. The most suitable eutectic solvents were choline chloride with either urea, oxalic or levulinic acid. The use of deep eutectic solvents has several advantages: environmental benignity, biodegradability, easy purification and simple preparation. All tested compounds showed antifungal activities against Botrytis cinerea, Colletotrichum acutatum, Alternaria radicina and Fusarium graminearum at 10 and 100 µg/mL.

The crystal structures of six novel Ag+ complexes with NO3− and dihalopyridines revealed intriguing differences that were interpreted by DFT calculations.

The quaternization reactions of nicotinamide, with different electrophiles: methyl iodide and substituted 2-bromoacetophenones (4-Cl, 4-Br, 4-H, 4-CH3, 4-F, 4-OCH3, 4-Ph, 2-OCH3, 4-NO2) are reported. The preparations were carried out by conventional synthesis and under microwave irradiation in absolute ethanol and acetone. The synthesis performed by microwave dielectric heating significantly improved yield, up to 8 times, and shortened down the reaction time from ca. one day in conventional, to 10–20 min. The structures of the synthesized compounds were confirmed by IR, 1H- and 13C-NMR spectroscopy, mass spectrometry and elemental analysis. The compounds have been screened for antifungal activities against Fusarium oxysporum, Fusarium culmorum, Macrophomina phaseolina and Sclerotinia sclerotiorum at concentrations of 10 µg/mL and 100 µg/mL. Six compounds showed the strong inhibition of mycelium growth at a concentration of 10 µg/mL. All tested compounds revealed the great inhibitory activities against S. sclerotiorum at a concentration of 100 µg/mL.

Ten novel isonicotinamide derivatives were prepared by quaternization reactions of isonicotinamide with methyl iodide and nine differently substituted 2 bromoacetophenones under rapid microwave irradiation of 10 minutes. The microwave preparations were significantly faster and with yields higher up to 8 times, than the preparations by conventional method. The structures of synthesized molecules were determined by one- and two dimensional NMR and IR spectroscopy, mass spectrometry and elemental analysis. Antifungal activity of all compounds was tested in two different concentrations (10 and 100 µg mL–1) against Fusarium oxysporum, Fusarium culmorum, Macrophomina phaseolina and Sclerotinia sclerotiorum in vitro. From the antifungal assay it can be seen that the most prepared compounds have moderate to weak activity against M. phaseolina and F. culmorum. A very high inhibitory rate was observed against S. sclerotiorum, 62–87.5 % in concentration of 10 µg mL–1 and 83.7–93.2 % in concentration of 100 µg mL–1.

Shortcomings of the correlation coefficient (Pearson's) as a measure for estimating and calculating the accuracy of predictive model properties are analysed. Here we discuss two such cases that can often occur in the application of the model in predicting properties of a new external set of compounds. The first problem in using the correlation coefficient is its insensitivity to the systemic error that must be expected in predicting properties of a novel external set of compounds, which is not a random sample selected from the training set. The second problem is that an external set can be arbitrarily large or small and have an arbitrary and uneven distribution of the measured value of the target variable, whose values are not known in advance. In these conditions, the correlation coefficient can be an overoptimistic measure of agreement of predicted values with the corresponding experimental values and can lead to a highly optimistic conclusion about the predictive ability of the model. Due to these shortcomings of the correlation coefficient, the use of standard error (root-mean-square-error) of prediction is suggested as a better quality measure of predictive capabilities of a model. In the case of classification models, the use of the difference between the real accuracy and the most probable random accuracy of the model shows very good characteristics in ranking different models according to predictive quality, having at the same time an obvious interpretation.

A non-covalent self-assembled chiral alanyl aminopyridine ligand exhibits supramolecular chirality in solution, independent of the organic solvent used. The supramolecular chirality of the assemblies is completely inverted by complexation to zinc ions. To date, such a supramolecular metal-ligand system has not been reported in the literature.