Structural and magnetic properties of Ru/Ni multilayers

International audienceRu/Ni multilayers of different Ni thickness have been fabricated using magnetron sputtering. The structure of the multilayers has been determined by grazing incidence X-ray diffraction and X-ray reflectivity and their magnetic properties by magnetization and polarized neutron reflectivity measurements. The presence of Ru leads to the formation of a hexagonal Ni structure within interfacial layer ~1 nm above each Ru layer, while the rest of the Ni layer relaxes to the equilibrium fcc structure. The hcp Ni interfacial layer has a substantially increased cell volume is ferromagnetic with an atomic magnetic moment that increases with Ni layer thickness but remains lower than the value predicted from ab initio calculations

Nanovesicles loaded with origanum onites and satureja thymbra essential oils and their activity against food-borne pathogens and spoilage microorganisms

Food poisoning is a common cause of illness and death in developing countries. Essential oils (EOs) could be effective and safe natural preservatives to prevent and control bacterial contamination of foods. However, their high sensitivity and strong flavor limit their application and biological effectiveness. The aim of this study was firstly the chemical analysis and the antimicrobial evaluation of the EOs of Origanum onites L. and Satureja thymbra L. obtained from Symi island (Greece), and, secondly, the formulation of propylene glycol-nanovesicles loaded with these EOs to improve their antimicrobial properties. The EOs were analyzed by GC-MS and their chemical contents are presented herein. Different nanovesicles were formulated with small average sizes, high homogeneity, and optimal ζ-potential. Microscopic observation confirmed their small and spherical shape. Antibacterial and antifungal activities of the formulated EOs were evaluated against food-borne pathogens and spoilage microorganisms compared to pure EOs. Propylene glycol-nanovesicles loaded with O. onites EO were found to be the most active formulation against all tested strains. Additionally, in vitro studies on the HaCaT cell line showed that nanovesicles encapsulated with EOs had no toxic effect. The present study revealed that both EOs can be used as alternative sanitizers and preservatives in the food industry, and that their formulation in nanovesicles can provide a suitable approach as food-grade delivery system

Phytochemical study of Stachys candida Bory & Chaubard (Lamiaceae)

Phytochemical analysis of the aerial parts of Stachys candida Bory & Chaubard, growing wild in Greece led to the isolation of eleven bioactive secondary metabolites. Nine flavones, one of them methylated, one phenylethanoid glycoside and one phenolic acid were isolated from the methanol extract of this plant. The structure elucidation of the isolated compounds was achieved on the basis of NMR spectroscopy (1D and 2D spectra). The phytochemical profile was appeared to be similar with other Greek endemic Stachys species, while a strong difference was the absence of iridoids. Importantly, the chemotaxonomic significance of the isolated compounds has extensively been described. © 2020 Elsevier Lt

The Effect of Successive Harvesting on The Volatile Constituents of Two Essential Oils of Cultivated Populations of Sea Fennel (Crithmum maritimum L.) in Greece

Crithmum maritimum L. (Apiaceae), known as Sea fennel, is a perennial plant, growing wild mainly on maritime rocks along with the Mediterranean countries, Pacific and Atlantic coasts. Traditionally, various parts of this plant have been used as a tonic, antiscorbutic, carminative, vermifuge and diuretic. Over the last years, the essential oil (EO) of sea fennel is widely used in the food and cosmetic industry. In the present study, the EOs of the aerial parts obtained from cultivated populations of two consecutive years (2016; 2017; Larissa-Central Greece) were analyzed by GC/MS. The main compounds of the EO derived from the cultivar of 2016 were sabinene (17.6 %), γ-terpinene (17.5 %), p-cymene (16.7 %), β-phellandrene (15.5 %), thymol methyl ether (9.3 %), terpinen-4-ol (4.8 %) and dillapiole (2.0 %). Though, the sample of 2017 included β-phellandrene (30.9 %), γ-terpinene (19.6 %), sabinene (15.8 %), thymol methyl ether (7.6 %), terpinen-4-ol (4.8 %) and dillapiole (0.1 %). A comparison was made between the two samples, as well as with the previous literature data. This is the first study deals with the chemical analysis of EOs from Greek cultivated C. maritimum. Our data revealed the presence of monoterpene hydrocarbons as the major constituents in both EOs and confirmed the presence of dillapiole in the Greek EOs of the specific plant. © 2021 Har Krishan Bhalla & Sons

Cultivation strategy to improve chemical profile and anti-oxidant activity of Sideritis perfoliata L. subsp. perfoliata

Due to the remarkable medicinal properties of Sideritis spp, the commercial demand for the plant is continuously on the rise both in the European and in the global market. Cultivation of Sideritis species have been occurred to successfully meet the need for mass production of high-quality plant material. The present study was undertaken in order to investigate the impact of different cultivation practices (conventional versus organic cultivation; full versus deficit irrigation) in the yield and phytochemical profile of S. perfoliata L. subsp. perfoliata from Cyprus, under two harvestings for biomass production. Deficit irrigation decreased plant growth, but increased dry matter content. The content of chlorophylls and the nitrogen and potassium content decreased in organically grown plants. Both organic cultivation and/or deficit irrigation increased total phenolics, flavonoids, vitamin C and antioxidants. Essential oil yield increased under deficit irrigation at the 2nd harvest, while essential oil composition fluctuated among the treatments. Infusions of each plant material were prepared according to the European Medicines Agency (EMA) monograph. Based on their NMR spectra, the deficit-irrigated plants from conventional cultivation were the most rich in secondary metabolites and chosen for further chemical analysis. Six iridoids such as three flavonoids, two phenylethanoid glucosides and one phenolic acid have been isolated indicating new knowledge on the effects of cultivation practices on plant secondary metabolisms with putative industrial applications and interest. © 2019 Elsevier B.V

Nanovesicles loaded with origanum onites and satureja thymbra essential oils and their activity against food-borne pathogens and spoilage microorganisms

Food poisoning is a common cause of illness and death in developing countries. Essential oils (EOs) could be effective and safe natural preservatives to prevent and control bacterial contamination of foods. However, their high sensitivity and strong flavor limit their application and biological effectiveness. The aim of this study was firstly the chemical analysis and the antimicrobial evaluation of the EOs of Origanum onites L. and Satureja thymbra L. obtained from Symi island (Greece), and, secondly, the formulation of propylene glycol-nanovesicles loaded with these EOs to improve their antimicrobial properties. The EOs were analyzed by GC-MS and their chemical contents are presented herein. Different nanovesicles were formulated with small average sizes, high homogeneity, and optimal ζ-potential. Microscopic observation confirmed their small and spherical shape. Antibacterial and antifungal activities of the formulated EOs were evaluated against food-borne pathogens and spoilage microorganisms compared to pure EOs. Propylene glycol-nanovesicles loaded with O. onites EO were found to be the most active formulation against all tested strains. Additionally, in vitro studies on the HaCaT cell line showed that nanovesicles encapsulated with EOs had no toxic effect. The present study revealed that both EOs can be used as alternative sanitizers and preservatives in the food industry, and that their formulation in nanovesicles can provide a suitable approach as food-grade delivery system. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Traditionally used sideritis cypria post.: Phytochemistry, nutritional content, bioactive compounds of cultivated populations

Sideritis species are recognized as important medicinal plants and their commercial demand is continuously on the rise both in the European and in the global market. Consequently, the cultivation of Sideritis species has been occurred to successfully meet the need for mass production of high-quality plant material. The present study was undertaken in order to investigate the chemical composition of cultivated S. cypria. Infusions of flowers and leaves were prepared separately, according to the European Medicine Agency (EMA) monograph. The infusion of the flowers revealed the presence of four flavones, isoscutellarein-7-O-[6′″-O-acetyl-β-D-allopyranosyl-(1→2)-β-D-glucopyranoside, its 4′-O-methyl-derivative, 4′-O-methyl-hypolaetin-7-O-[6′″-O-acetyl-β-D-allopyranosyl-(1→2)-β-D-glucopyranoside, and isoscutellarein-7-O-[6′″-O-acetyl-β-D-allopyranosyl-(1→2)]-6″-O-acetyl-β-D-glucopyranoside; four phenylethanoid glucosides, acteoside, leucosceptoside A, lamalboside, and leonoside A; one iridoid, melittoside, and one phenolic acid, chlorogenic acid, while the infusion of the leaves of the same population afforded the same first two flavones; five phenylethanoid glucosides, acteoside, leucosceptoside A, lavandulifolioside, leonoside A, and lamalboside; melittoside and chlorogenic acid. The structural elucidation of the isolated compounds was undertaken by high-field NMR spectroscopy. Moreover, the essential oils of the flowers and leaves were studied by GC-MS, separately. In addition, the mineral, bioactive compounds, protein and carbohydrate contents were evaluated for both plant materials. © 2020 Lytra, Tomou, Chrysargyris, Drouza, Skaltsa and Tzortzakis

Weak ferromagnetism and exchange biasing in cobalt oxide nanoparticle systems

Cobalt oxide nanoparticle systems have been prepared by wet chemical processing involving the encapsulation of the nanoparticles by an organic ligand shell (oleic acid and oleylamine). CoO nanoparticles were easily prepared by this method, while the synthesis of the CoPt/CoO nanocomposites was achieved using a two step polyol process. CoPt nanoparticles were first obtained by simultaneous reduction of cobalt acetate and platinum acetylacetonate and then used as seeds for the growth upon them of cobalt oxide using a second polyol process. The antiferromagnetic CoO nanoparticles, when field cooled to temperatures below 200 K, show displacement of the magnetization curves (along the magnetization axis) characteristic of weak ferromagnetism phenomena that are attributed to the uncompensated surface magnetic moments. The transition temperature of the particles is considerably lower than the Néel temperature of CoO and it is followed by an upswing at low temperatures, which is attributed to spins that are loosely coupled to the antiferromagnetic core. In the CoPt/CoO nanocomposites, magnetic measurements show the appearance of increased coercivity with respect to the as-prepared CoPt particles and unidirectional anisotropy (loop shift of Heb=1125 Oe) at temperatures below 20 K, as a result of exchange coupling between CoO and CoPt.