Determination of triazine herbicides: development of an electroanalytical method utilizing a solid amalgam electrode that minimizes toxic waste residues, and a comparative study between voltammetric and chromatographic techniques

The use of a copper solid amalgam electrode (CuSAE) for the analytical determination of triazine herbicides (atrazine and ametryne) instead of the conventional hanging mercury drop electrode (HMDE) is reported. The results obtained using electroanalytical methods utilizing each of these electrodes were also compared with those provided by the HPLC technique. The results indicated that the CuSAE electrode can be used to detect the herbicides studied, since the detection limits reached using the electrode (3.06 μg L⁻¹ and 3.78 μg L⁻¹ for atrazine and ametryne, respectively) are lower than the maximum values permitted by CONAMA (Brazilian National Council for the Environment) for wastewaters (50 μg L⁻¹) and by the US EPA (Environmental Protection Agency of the United States) in natural water samples (10.00 μg L⁻¹). An electroanalytical methodology employing CuSAE and square wave voltammetry (SWV) was successfully applied to the determination of atrazine and ametryne in natural water samples, yielding good recoveries (70.30%–79.40%). This indicates that the CuSAE provides a convenient substitute for the HMDE, particularly since the CuSAE minimizes the toxic waste residues produced by the use of mercury in HDME-based analyses.     

Latrunculin analogues with improved biological profiles by "diverted total synthesis": preparation, evaluation, and computational analysis

Deliberate digression from the blueprint of the total syntheses of latrunculin A (1) and latrunculin B (2) reported in the accompanying paper allowed for the preparation of a focused library of "latrunculin-like" compounds, in which all characteristic structural elements of these macrolides were subject to pertinent molecular editing. Although all previously reported derivatives of 1 and 2 were essentially devoid of any actin-binding capacity, the synthetic compounds presented herein remain fully functional. One of the designer molecules with a relaxed macrocyclic backbone, that is compound 44, even surpasses latrunculin B in its effect on actin while being much easier to prepare. This favorable result highlights the power of "diverted total synthesis" as compared to the much more widely practiced chemical modification of a given lead compound by conventional functional group interconversion. A computational study was carried out to rationalize the observed effects. The analysis of the structure of the binding site occupied by the individual ligands on the G-actin host shows that latrunculin A and 44 both have similar hydrogen-bond network strengths and present similar ligand distortion. In contrast, the H-bond network is weaker for latrunculin B and the distortion of the ligand from its optimum geometry is larger. From this, one may expect that the binding ability follows the order 1 >/= 44 > 2, which is in accord with the experimental data. Furthermore, the biological results provide detailed insights into structure/activity relationships characteristic for the latrunculin family. Thus, it is demonstrated that the highly conserved thiazolidinone ring of the natural products can be replaced by an oxazolidinone moiety, and that inversion of the configuration at C16 (latrunculin B numbering) is also well accommodated. From a purely chemical perspective, this study attests to the maturity of ring-closing alkyne metathesis (RCAM) catalyzed by a molybdenum alkylidyne complex generated in situ, which constitutes a valuable tool for advanced organic synthesis and natural product chemistry.     

Dissociative photoionization of adenine following valence excitation

We present results on the valence level excitation, ionization and dissociation of adenine, using time-of-flight mass spectrometry and synchrotron radiation, in the vacuum ultraviolet (VUV) range of 12-21 eV. The measurements were performed using a gas-phase (Ne) harmonics filter in order to eliminate contributions from higher-order harmonics. Mass spectra were obtained using the photoelectron-photoion coincidence technique (PEPICO). The relative abundances for each ionic fragment and their mean kinetic energy release have been determined from the analysis of the corresponding peak shapes in the mass spectra. Comparison with the available photoelectron spectra and previous measurements allowed the assignment of the main features in the spectra. A discussion on the dissociative photoionization channels of this molecule has also been included. Due to our harmonics-free incident photon beam we were able to propose new appearance energy (AE) for the most important ionic channels in this energy range. The precursor ion, C(5)H(5)N(5)+, is the most abundant species (40% at 15 eV and 20% at 20 eV), which confirms the high stability of adenine upon absorption of VUV photons. We have observed other intense fragment ions such as: C(4)H(4)N(4)+, C(3)H(3)N(3) (+), C(2)H(2)N(2)+ and HCNH+. The production of the neutral HCN fragment represents up to 40% of the dissociative channels for this molecule as induced by VUV photons.     

Thalidomide analogs from diamines: Synthesis and evaluation as inhibitors of TNF-alpha production

Fourteen thalidomide analogs bearing two phthalimido units were prepared in high yields (83-94%) by condensation of different diamines with phthalic or 3-nitrophthalic anhydride. An in vitro investigation of the compounds as inhibitors of the TNF-alpha production was performed. The inhibition was higher for compounds bearing amino and nitro groups and was modulated by increasing the size of the spacers between the phthalimide groups.     

Nanoparticles of octakis[3-(3-amino-1,2,4-triazole)propyl]octasilsesquioxane as ligands for Cu(II), Ni(II), Cd(II), Zn(II), and Fe(III) in aqueous solution

Nanoparticles of octakis[3-(3-amino-1,2,4-triazole)propyl]octasilsesquioxane (ATZ-SSQ) were tested as ligands for transition-metal ions in aqueous solution with a special attention to sorption isotherms, ligand-metal interaction, and determination of metal ions in natural waters. The adsorption potential of the material ATZ-SSQ was compared with related [3(3-amino-1,2,4-triazole)propyl]silica gel (ATZ-SG). The adsorption was performed using a batchwise process and both organofunctionalized surfaces showed the ability to adsorb the metal ions from aqueous solution. The Langmuir model was used to simulate the sorption isotherms. The results suggest that the sorption of these metals on ATZ-SSQ and ATZ-SG occurs mainly by surface complexation. The equilibrium condition is reached at time lower than 3 min for ATZ-SSQ, while for ATZ-SG is only reached at time of 25 min. The maximum metal ion uptake values for ATZ-SSQ were higher than the corresponding values achieved with the ATZ-SG. In order to obtain more information on the ligand-metal interaction of the complexes on the surface of the ATZ-SSQ nanomaterial, ESR study with various degrees of copper loadings was carried out. The ATZ-SSQ was tested for the determination (in flow using a column technique) of the metal ions present in natural waters.     

Catechins: Therapeutic Perspectives in COVID-19-Associated Acute Kidney Injury

Data obtained from several intensive care units around the world have provided substantial evidence of the strong association between impairment of the renal function and in-hospital deaths of critically ill COVID-19 patients, especially those with comorbidities and requiring renal replacement therapy (RRT). Acute kidney injury (AKI) is a common renal disorder of various etiologies characterized by a sudden and sustained decrease of renal function. Studies have shown that 5–46% of COVID-19 patients develop AKI during hospital stay, and the mortality of those patients may reach up to 100% depending on various factors, such as organ failures and RRT requirement. Catechins are natural products that have multiple pharmacological activities, including anti-coronavirus and reno-protective activities against kidney injury induced by nephrotoxic agents, obstructive nephropathies and AKI accompanying metabolic and cardiovascular disorders. Therefore, in this review, we discuss the anti-SARS-CoV-2 and reno-protective effects of catechins from a mechanistic perspective. We believe that catechins may serve as promising therapeutics in COVID-19-associated AKI due to their well-recognized anti-SARS-CoV-2, and antioxidant and anti-inflammatory properties that mediate their reno-protective activities.     

Darstellung und Kristallstrukturen von Silber(I)-Gemischtligandkomplexen mit Bibenzimidazol und Triphenylphosphan: [Ag(PPh3)2(bbimH2)](COOCH3) · 2 CH2Cl2 und [{Ag(PPh3)2}2(μ-bbim)] · 4 CH2Cl2

Preparation and Crystal Structures of Silver(I) Mixed Ligand Complexes with Bibenzimidazole and Triphenylphosphane: [Ag(PPh₃)₂(bbimH₂)](COOCH₃) · 2 CH₂Cl₂ and [{Ag(PPh₃)₂}₂(μ-bbim)] · 4 CH₂Cl₂ The title compounds are obtained from silver acetate, 2,2′-bibenzimidazole and PPh₃. They are characterized by their IR, ¹H-NMR, ³¹P-NMR spectra and crystal structure determinations. [Ag(PPh₃)₂(bbimH₂)](COOCH₃) · 2 CH₂Cl₂: Reaction in CH₂Cl₂. Space group C2/c, Z = 4, 3129 observed unique reflections, R = 0.033. Lattice parameters at 203 K: a = 1450.8; b = 1556.2; c = 2316.4 pm; β = 99.69°. The crystal structure is built up by monomeric molecules with distorted tetrahedral coordination of the silver atom (AgP₂N₂) and bibenzimidazole as a bidentate ligand. The acetate ion is linked to the NH-groups of the bibenzimidazole by hydrogen bonds. [{Ag(PPh₃)₂}₂(μ-bbim)] · 4 CH₂Cl₂: Reaction in fused PPh₃ at 180 °C. Space group P 1, Z = 1. 9227 observed unique reflections, R = 0.051. Lattice parameters at 203 K: a = 1276.5; b = 1352.1; c = 1408.1 pm; α = 96.97; β = 115.87; γ = 96.84°. The crystal structure is built up by centrosymmetric molecules with distorted tetrahedral coordination of the silver atoms (AgN₂P₂) and bibenzimidazolate(2–) as tetradentate bridging ligand.     

Effect of the alkylaluminum cocatalyst on ethylene polymerization by a nickel–diimine complex

Different chlorine-free alkylaluminum compounds were active cocatalysts for ethylene polymerization in the presence of 1,4-bis(2,6-diisopropylphenyl)-acenaphthenediimine-dichloronickel (II) (1). The combination of 1 with trimethylaluminum or triisobutylaluminum produced catalytically active species that polymerized ethylene with productivities up to 469 kg_polymer/(mol_Ni · h). The activity of the catalytic system and the properties of the polymeric materials were influenced strongly by the reaction temperature. The polymers had a high molecular weight (up to 642 × 10³ g · mol⁻¹), and the molecular weight increased with the reaction time. The polyethylenes were branched, and the branching could be modulated by the proper choice of reaction parameters. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4656–4663, 1999     

Human Group IIA Phospholipase A2—Three Decades on from Its Discovery

Phospholipase A₂ (PLA₂) enzymes were first recognized as an enzyme activity class in 1961. The secreted (sPLA₂) enzymes were the first of the five major classes of human PLA₂s to be identified and now number nine catalytically-active structurally homologous proteins. The best-studied of these, group IIA sPLA₂, has a clear role in the physiological response to infection and minor injury and acts as an amplifier of pathological inflammation. The enzyme has been a target for anti-inflammatory drug development in multiple disorders where chronic inflammation is a driver of pathology since its cloning in 1989. Despite intensive effort, no clinically approved medicines targeting the enzyme activity have yet been developed. This review catalogues the major discoveries in the human group IIA sPLA₂ field, focusing on features of enzyme function that may explain this lack of success and discusses future research that may assist in realizing the potential benefit of targeting this enzyme. Functionally-selective inhibitors together with isoform-selective inhibitors are necessary to limit the apparent toxicity of previous drugs. There is also a need to define the relevance of the catalytic function of hGIIA to human inflammatory pathology relative to its recently-discovered catalysis-independent function.     

Using a portable total reflection X-ray fluorescence system for a multielement analysis of Swiss mice brains with experimental Alzheimer's disease induced by β-amyloid oligomers

Alzheimer's disease (AD) is a progressive and irreversible disorder whose pathological features include β-amyloid (Aβ) plaques and neuronal and synaptic loss. Metals such as iron, copper, and zinc are increased in the brains of patients with AD. Those metals can interact with Aβ, resulting in the promotion of Aβ deposition and formation of plaque. However, no study analyzing the effects of single injection of Aβ soluble oligomers (AβOs) in the elements' homeostasis in mice was developed. Total reflection X-ray fluorescence (TXRF) is a multielement analytical technique that can be utilized to identify and quantify trace elements present in a sample at very low concentrations. In this study, in order to evaluate the concentration of metals in brain regions of Swiss mice, three groups of female mice and three of male mice were studied: control, AD10, and AD100. The AD groups received an AβOs intracerebroventricular injection so as to induce experimental AD. Afterwards, a craniotomy was performed, and six brain compartments were dissected and evaluated. TXRF measurements were performed using a portable TXRF system that uses an X-ray tube with a molybdenum anode and a detector Si-PIN. It is proved to determine the following elements' concentrations: phosphorus, sulfur, potassium, iron, copper, zinc, and rubidium. Results showed differences in the elemental concentration in some brain regions between AD groups. These alterations suggest that AβOs act quickly, even before the amyloid plaques' formation, explaining cognitive deficits independently of amyloid plaques. This study helped to understand that this modification on elemental concentration can be influenced by AβOs.