Iron reduction potentiates hydroxyl radical formation only in flavonols

Flavonoids, substantial components of the human diet, are generally considered to be beneficial. However, they may possess possible pro-oxidative effects, which could be based on their reducing potential. The aims of this study were to evaluate the ability of 26 flavonoids to reduce ferric ions at relevant pH conditions and to find a possible relationship with potentiation of hydroxyl radical production. A substantial ferric ions reduction was achieved under acidic conditions, particularly by flavonols and flavanols with the catecholic ring B. Apparently corresponding bell-shaped curves displaying the pro-oxidant effect of flavonols quercetin and kaempferol on iron-based Fenton reaction were documented. Several flavonoids were efficient antioxidants at very low concentrations but rather inefficient or pro-oxidative at higher concentrations. Flavonols, morin and rutin were progressively pro-oxidant, while 7-hydroxyflavone and hesperetin were the only flavonoids with dose-dependent inhibition of hydroxyl radical production. Conclusively, administration of flavonoids may lead to unpredictable consequences with few exceptions.     

Isolation and identification of a ferulic acid dehydrotrimer from saponified maize bran insoluble fiber

Following saponification of maize bran insoluble fiber a ferulic acid dehydrotrimer was isolated using Sephadex LH-20 chromatography. Structural identification was carried out using UV-spectroscopy, mass spectrometry and 1D and 2D NMR experiments ( ¹H, ¹³C, DEPT, COSY, TOCSY, ¹³C- ¹H HSQC, HMBC). UV-spectroscopy indicated characteristics of ferulate structures, mass spectrometry showed a trimeric ferulate structure, and the NMR spectra provided diagnostic evidence for its being a 5-5/8-O-4-coupled dehydrotrimer. Ferulic acid dehydrodimers are mainly derived from diferulates which cross-link polysaccharides. Because of the involvement of a 5-5-dehydrodiferulic acid unit in the identified trimer, this novel dehydrotriferulic acid from cereal grain fiber need not imply the cross-linking of three polysaccharide chains; molecular modeling of the ferulate dehydrodimerization in earlier studies showed that the 5-5-diferulate, uniquely, can form intramolecularly. This first identified ferulic acid dehydrotrimer nevertheless reveals that polysaccharide chains can be more extensively cross-linked than previously recognized.     

Advances in cultivar choice,hazelnut orchard management,and nut storage to enhance product quality and safety: an overview

European hazelnut (Corylus avellana L.) is a major species of interest for nutritional use within the Betulaceae family and its nuts are widely used throughout the world in the chocolate, confectionery, and bakery industries. Recently its cultivation has been expanded in traditional producer countries and established in new places in the southern hemisphere, including Chile, South Africa, and Australia. Introducing hazelnut in new environments could reduce its productivity, lead the trees to experience eco‐physiological disorders, and expose the crop to high pressure from common and new pests and diseases. Thus, new approaches in cultivar choice guidance, in the sustainable orchard management and even in nut storage and kernel quality evaluation are urgently required to improve the hazelnut production and processing chain. The main objective of this study was to systematize the published information regarding recent findings about the cultural operations that directly influence nut and kernel quality, support varietal choice for new plantations, and list the recent advances in nut storage and in quality and safety evaluation. © 2020 Society of Chemical Industry     

Determination of the percentage of wood failure by 3D scanning of the adhesive bondline

The quality of the wood-adhesive bond is usually determined by its shear strength and the percentage of wood failure, the latter usually being determined by visual evaluation and prone to the examiner’s subjective evaluation. A new technique of 3D scanning was used to evaluate the percentage of wood failure, and the results obtained were compared to those obtained by means of existing methods, i.e. the visual evaluation and image analysis techniques. Evaluation by 3D scanning showed comparable values for samples with a high percentage of wood failure, but large differences in the case of samples showing mainly adhesive failure.     

Purification and characterization of natural Bet v 1 from birch pollen and related allergens from carrot and celery

Birch pollen allergy is predominantly caused by the major allergen Bet v 1 and can lead to crossreactions with homologous proteins in food. Two major cross-reactive food allergens are Dau c 1 from carrot and Api g 1 from celery, which have never been purified from their natural source. Here, we describe a non-denaturing purification method for obtaining natural Bet v 1, Dau c 1 and Api g 1, comprising of ammonium sulfate precipitation, hydrophobic interaction chromatography and size exclusion chromatography. This method resulted in 98-99% pure isoform mixtures for each allergen. Characterization of these isoform mixtures with Q-TOF MS/MS clearly showed earlier reported isoforms of Bet v 1, Dau c 1 and Api g 1, but also new isoforms. The presence of secondary structure in the three purified allergens was demonstrated via circular dichroism and showed high similarity. The immune reactivity of the natural allergens was compared with recombinant proteins by Western blot and ELISA and showed similar reactivity.     

Oestrogen and progesterone receptors in the marmoset endometrium: changes during the ovulatory cycle, early pregnancy and after inhibition of vascular endothelial growth factor, GnRH or ovariectomy

Marmosets are widely used, but detailed studies on localisation of endometrial oestrogen receptors alpha and beta (ER alpha and ER beta ), and the progesterone receptor (PR) are lacking. These receptors were localised and semi-quantitatively analysed throughout the ovulatory cycle, weeks 2, 3 and 4 of pregnancy and after treatment with GnRH antagonist, vascular endothelial growth factor (VEGF) Trap or ovariectomy. The PR in epithelial cells increased markedly between the mid- and late proliferative phases before declining in the mid-secretory phase and pregnancy. PR in stromal cells was present throughout the cycle and levels were maintained in pregnancy. ER alpha was present at the mid-proliferative phase and increased in glands at the late proliferative and early secretory phases, before declining at the late secretory phase and week 4 of pregnancy. Stromal ER alpha showed a similar trend, but decreased earlier, by the mid-secretory phase. ER beta was highly expressed in epithelial cells throughout the cycle and in pregnancy. In stroma, increases in ER beta expression were observed at the late proliferative phase with the staining index decreasing by half as the secretory phase progressed and in pregnancy. GnRH antagonist, VEGF Trap or ovariectomy caused significant reductions in PR and ER beta expression, but not in ER alpha when compared with the late proliferative phase of the normal cycle. Endothelial cells expressed ER beta , but not ER alpha or PR. It is concluded that the steroid receptor profile in the marmoset endometrium is generally similar to the human and should provide a useful model for studies on hormonal manipulation of the endometrium.     

A new extra situ sol–gel route to silica/epoxy (DGEBA) nanocomposite. A DTA study of imidazole cure kinetic

Silica nanoparticles were obtained through the Stöber method, from mixtures of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTS). The nanoparticles were dispersed in tetrahydrofuran (THF) and coupled to bisphenol A epoxy resin (DGEBA) through surface amino groups. After removing THF non-isothermal cure was performed at different heating rates (2–20°C/min), using imidazole (2–4 wt%) as curing agent. For the sake of comparison bare DGEBA epoxy polymers were also prepared with similar schedule A nanocomposite of well-dispersed silica nanoparticles (5 wt%) in a fully cured epoxy matrix was easily obtained. Lower cure kinetics were observed with silica addition. This was attributed to reduction of the imidazole volume concentration. Cure activation energy was not influenced by silica presence, whereas it changed with the imidazole content. Therefore, experimental results suggested that silica had only an indirect effect (the reduction of the imidazole molar concentration) on the epoxy matrix cure kinetics. Glass transformation temperatures, T _g, as high as 175°C were recorded. The nanocomposite glass transformation temperature depended on the heating rate of the cure process, the imidazole and silica content. T _g changes as high as 40°C were detected as a function of the heating rate. At higher imidazole content no differences in T _g values between bare polymer and the nanocomposite were observed. This suggests that a higher imidazole content assures a better interconnection between the compatibilizing epoxy shell around the nanoparticles and the epoxy matrix. The new proposed methodology is an easy route to engineer both nanocomposites structure and interfacial interactions, thus tailoring their properties.     

Consolidation and mechanical properties of reactive nanocomposite powders

Reactive nanocomposite powders with bulk compositions of 8Al·MoO₃, 12Al·MoO₃, and 8Al·3CuO were prepared by arrested reactive milling (ARM) and consolidated into cylindrical and rectangular pellets using a uniaxial die. Pellets were pressed at room temperature without any binder. Reference pellets were prepared from conventional Al powder and from Al-metal oxide powder blends with bulk compositions identical to those of the nanocomposite powders. Materials could be consolidated to densities greater than 90% of the theoretical maximum density while maintaining their high reactivity. Tensile strength and flexural strength of the consolidated materials were measured using diametrical compression and three-point flexural strength tests, respectively. Higher strengths were observed for higher relative densities, and the strength of the composite materials was comparable to that of consolidated aluminum powders. Yield strength of the reactive nanocomposite powders was determined from compaction load vs. die displacement curves using the Heckel equation. It was greater for the nanocomposite powders as compared to the powder blends or pure aluminum. Organic, or low melting point metal binders were added to selected samples to improve strength. Respective pellets were pressed at temperatures above the melting point of the metal binder. The highest density (~ 2.9 g/cm³) and tensile strength (~ 17.5 MPa) was observed with indium as binder. All consolidated samples were found to be highly reactive, and the effect of partial reaction during consolidation remained below the limit quantifiable by differential scanning calorimetry.     

Adhesive bonding of 3D-printed ABS parts and wood

Additive manufacturing, also known as 3D printing technology, has experienced massive growth in the last decade. Instead of printing the entire product, 3D printing can be used to produce only the most complex parts, which are then combined with simple, non-printed parts from other materials to make the final product. In addition to mechanical connections, adhesive bonding is most commonly used to combine printed parts with other elements. In this study, the influence of 3D-printing parameters on the bond shear strength of 3D-printed Acrylonitrile-butadiene-styrene copolymer parts bonded to beech wood was investigated. Three printing settings with different layer thicknesses (0.39, 0.19, 0.09 mm) and a posttreatment method that utilized acetone vapour were used. The three different adhesives applied were commercial one-component polyurethane adhesive, hot melt adhesive for edge bonding, and a two-component polyurethane adhesive. The results show that the type of adhesive had the biggest influence on the strength of the bond. The highest bond strength was achieved using a two-component polyurethane adhesive. The type of failure (failure in wood, plastic, adhesive, or cohesive failure) depended greatly on the type of adhesive and thickness of the printed layer.