Chromatographic Determination of Total Selenium in Biofortified Allium sp. following Piazselenol Formation and Micro-Solid-Phase Extraction

Herein, a method based on selective piazselenol formation is applied for total selenium determination in biofortified Allium species. Piazselenol is formed by reacting Se(IV) with an aromatic diamine, namely 4-nitro-1,2-phenylenediamine, in acidic medium. Samples were digested in a nitric acid/hydrogen peroxide open system, followed by selenate reduction in hydrochloric acid. Reaction conditions were optimized in terms of pH, temperature, reaction time, and other auxiliary reagents for interference removal, namely, EDTA and hydroxylamine. For the extraction of the selectively formed 4-nitro-piazselenol, micro-solid-phase extraction (μSPE) was applied, and the analysis and detection of the corresponding complex was performed by HPLC coupled with DAD. An external standard calibration curve was developed (R2 = 0.9994) with good sensitivity, and was used to calculate the total selenium content from several Allium plants material, with good intermediate precision (RSD% < 16%). The accuracy of the method was evaluated using both, a comparison with an accepted reference method from our previously published data, as well as three certified reference material with recoveries between 84–126%. The limit of detection was determined to be 0.35 μg/g (in solids) and 1.1 μg/L (in solution), while the limit of quantification was 1.07 μg/g and 3.4 μg/L (in solution). Using the proposed method, selenium content can be quickly and accurately determined in several types of samples. In addition, this study present experimental conditions for overcoming the interferences that might be encountered in selenium determination using piazselenol

"Yellow" laccase from Sclerotinia sclerotiorum is a blue laccase that enhances its substrate affinity by forming a reversible tyrosyl-product adduct.

Yellow laccases lack the typical blue type 1 Cu absorption band around 600 nm; however, multi-copper oxidases with laccase properties have been reported. We provide the first evidence that the yellow laccase isolated from Sclerotinia sclerotiorum is obtained from a blue form by covalent, but nevertheless reversible modification with a phenolic product. After separating the phenolics from the extracellular medium, a typical blue laccase is obtained. With ABTS as model substrate for this blue enzyme, a non-natural purple adduct is formed with a spectrum nearly identical to that of the 1:1 adduct of an ABTS radical and Tyr. This modification significantly increases the stability and substrate affinity of the enzyme, not by acting primarily as bound mediator, but by structural changes that also alters the type 1 Cu site. The HPLC-MS analyses of the ABTS adduct trypsin digests revealed a distinct tyrosine within a unique loop as site involved in the modification of the blue laccase form. Thus, S. sclerotiorum yellow laccase seems to be an intrinsically blue multi-copper oxidase that boosts its activity and stability with a radical-forming aromatic substrate. This particular case could, at least in part, explain the enigma of the yellow laccases

Polyphenolic Composition, Antioxidant and Antibacterial Activities for Two Romanian Subspecies of Achillea distans Waldst. et Kit. ex Willd.

The aim of this work was to study the chemical composition, antioxidant and antibacterial properties of Achillea distans Waldst. et Kit. subsp. distans and Achillea distans Waldst. et Kit. subsp. alpina Rochel, from the Rodna Mountains (Romania). The identification and quantification of major phenolic compounds was performed by a HPLC-MS method. The total polyphenolic and flavonoid content was determined spectrophotometrically. The antioxidant activity was evaluated using the DPPH bleaching method, trolox equivalent antioxidant capacity assay (TEAC), hemoglobin ascorbate peroxidase activity inhibition (HAPX) assay, and an Electron Paramagnetic Resonance (EPR) spectroscopy method. A data indicated that A. distans subsp. alpina extract has more antioxidant activity than A. distans subsp. distans extract. Luteolin, apigenin, quercetin, caffeic and chlorogenic acids were present in the two extracts of A. distans, but in different amounts. Three flavonoids were detected only in A. distans subsp. alpina. The polyphenol-richer A. distans subsp. alpina extract showed a higher antioxidant activity than A. distans subsp. distans extract. A. distans subsp. distans extract showed inhibitory activity for Gram-positive bacteria, as evaluated with four species. The quantitative and qualitative differences between the two subspecies of Achillea distans could be used as a potential taxonomic marker in order to distinguish the species

Excess Ascorbate is a Chemical Stress Agent against Proteins and Cells

Excess ascorbate (as expected in intravenous treatment proposed for COVID-19 management, for example) oxidizes and/or degrades hemoglobin and albumin, as evidenced by UV-vis spectroscopy, gel electrophoresis, and mass spectrometry. It also degrades hemoglobin in intact blood or in isolated erythrocytes. The survival rates and metabolic activities of several leukocyte subsets implicated in the antiviral cellular immune response are also affected. Excess ascorbate is thus an unselective biological stress agent

Student Portrait, Westbrook Seminary and Junior College, 1930-34

Early 1930s Westbrook Seminary and Junior College individual student photographic portrait by Wilson Photo, Cambridge, Mass. In pencil on the back is written: C. Foss ?https://dune.une.edu/wchc_photos_students1930s/1003/thumbnail.jp

Antioxidant activity evaluation by physiologically relevant assays based on haemoglobin peroxidase activity and cytochrome <i>c</i>-induced oxidation of liposomes

<p>Two new protocols for exploring antioxidant-related chemical composition and reactivity are described: one based on a chronometric variation of a haemoglobin ascorbate peroxidase assay and one based on cytochrome <i>c</i>-induced oxidation of lecithin liposomes. Detailed accounts are given on their design, application, critical correlations with established methods and mechanisms. These assays are proposed to be physiologically relevant and bring new information regarding a real sample, both qualitative and quantitative. The well-known assays used for evaluation of antioxidant (re)activity are revisited and compared with these new methods. Extracts of the <i>Hedera helix</i> L. are examined as test case, with focus on seasonal variation and on leaf, fruit and flower with respect to chromatographic, spectroscopic and reactivity properties. According to the set of assays performed, winter are the most antioxidant, followed by summer leaves, and then by flowers and fruits.</p

Oxidative Protection of Hemoglobin and Hemerythrin by Cross-Linking with a Nonheme Iron Peroxidase: Potentially Improved Oxygen Carriers for Use in Blood Substitutes

The nonheme peroxidase, rubrerythrin, shows the ability to reduce hydrogen peroxide to water without involving strongly oxidizing and free-radical-creating powerful oxidants such as compounds I and II [formally Fe­(IV)] formed in peroxidases and catalases. Rubrerythrin could, therefore, be a useful ingredient in protein-based artificial oxygen carriers. Here, we report that the oxygen-carrying proteins, hemoglobin (Hb) and hemerythrin (Hr), can each be copolymerized with rubrerythrin using glutaraldehyde yielding high molecular weight species. These copolymers show additional peroxidase activity compared to Hb-only and Hr-only polymers, respectively and also generate lower levels of free radicals in reactions that involve hydrogen peroxide. Tests on human umbilical vein endothelial cells (HUVEC) reveal slightly better performance of the Rbr copolymers compared to controls, as measured at 24 h, but not at later times

Serum biochemistry of control and experimental animals.

<p>Values are expressed as mean ± SEM.</p