Ab initio study of the magnetic configurations on the (0 0 1) surfaces of binary FePd and FeRh ordered alloys

Ab initio calculations of the local spin polarization at the (0 0 1) surfaces performed on the binary FePd and FeRh alloys are presented. For Rh-terminated FeRh (0 0 1) surface, the calculations indicate a possible magnetic reconstruction leading to a ferromagnetic order in the surface region, in contrast to the AF-II ground state of the infinite bulk FeRh alloy

Microwave assisted extraction of bioactive saponins from the starfish Echinaster sepositus: Optimization by response surface methodology and comparison with ultrasound and conventional solvent extraction

International audienceMicrowave assisted extraction (MAE) was investigated for the extraction of total saponins compounds from the starfish Echinaster sepositus. In order to achieve optimization of microwave extraction and to determine the influence of each operational variable (the solvent concentration (X1), irradiation time (X2), microwave power (X3), and liquid-solid ratio (X4)) on the extraction of saponins, response surface methodology (RSM) coupled with a Box–Behnken design (BBD) was applied. The optimized experimental conditions were 58.7 % aqueous methanol as solvent, 177 W as microwave power for 3 min irradiation time at 43.6 mL g−1 of liquid-solid ratio. The extraction yield under these conditions was 60.3 ± 0.6 mg g−1. The optimized MAE was compared with other methods, ultrasound assisted extraction (UAE) and with conventional solvent extraction (CSE). It was demonstrated that microwave produced saponins extraction 7.8 times as more as that produced by CSE and 3.3 as more as UAE has produced. From the in vitro hemolytic tests and electro-generated O2[rad]− quenching tests, we have noted that the microwave saponins extract was the most active one comparing with both UAE and CSE extracts

Saponin contents in the starfish Echinaster sepositus: Chemical characterization, qualitative and quantitative distribution

International audienceIn this study, we report the inter-organ, the sexual and the seasonal variability, of saponins contained in the common Mediterranean starfish Echinaster (Echinaster) sepositus. Saponins were extracted from five distinct body components namely the stomach, the pyloric caeca, the gonads, the oral body wall and aboral body wall. Of both sexes (males and females) collected at different seasons, the saponins mixtures were analyzed by Mass spectrometry (HR-ESI-MS and HR-ESI- MS/MS). Semi-quantitative approach was performed to estimate the variability of the saponin amounts. Our results demonstrated that the diversity of saponins in E. sepositus is higher than previously reported. We highlighted 11 different saponins, including 9 new congeners. Presumptive molecular structures are proposed for 6 molecules on the basis of key-fragmentations identified by HR-ESI-MS/MS. The comparison of the saponin contained in the five different body components revealed that minimum 3 saponins are common in all tissues. In addition, qualitative and quantitative variability of saponins compounds were linked to the organ, sex and the collecting season. The relative highest level of saponins was found in the stomach on the period of active feeding (winter). The significant higher levels of saponins were found in the gonads and oral body wall on the spawning period (summer). Generally, a great inter-organ, sexual and seasonal variability was found in both sexes. These results suggest that saponins probably fulfill several biological functions in E. sepositus. © 2021 Elsevier Lt

Removal of Methylene Blue from aqueous solutions by adsorption on Kaolin: Kinetic and equilibrium studies

International audienceRemoval of Methylene Blue (MB) from aqueous solutions is studied using a raw Algerian kaolin sample as a low-cost adsorbent. The effects of pH, contact time, dye concentration and temperature are all taken into consideration. The adsorption kinetics results are adjusted to best fit the pseudo-second order model. The experimental data are analyzed by Langmuir isotherms, revealing that the maximum adsorption capacity of MB on this kaolin sample equals 52.76 mg/g at T = 25 °C and pH = 6.0. The calculated thermodynamic data demonstrates that adsorption is spontaneous and enhanced at higher temperatures. Desorption studies with water indicate that the adsorbent could successfully retain MB, even after four cycles. From these results, it can be considered that the raw Algerian kaolin sample tested herein is effective in the removal of MB from aqueous solutions and moreover may be used as an alternative to high-cost commercial adsorbents. © 2017 Elsevier B.V

Seedless table grape residues as a source of polyphenols: comparison and optimization of non-conventional extraction techniques

Grape skins are one of the most important leftovers of grape juice production, and are also a good source of bioactive compounds, especially phenolic antioxidants and fiber, because they are not stressed as the winemaking process occurs. Their extracts may be used as functional components of enriched foods and beverage, both to color the products and to supplement with bio-functional metabolites. Therefore, in this work, ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE) were optimized and compared using response surface methodology (RSM) and desirability function (D) statistical tools, at selected temperature and solvent type (close to 50 °C and water/ethanol/phosphoric acid 70:30:1) but varying contact time (t) and sample-to-solvent ratio (S/L), to find the best conditions for the extraction of the main polyphenols present in table grape skin (Apulia Rose cv.) residues from juice processing. The mathematical models built in this investigation showed that the highest significant factor (P < 0.001) was t, influencing the extraction of all compounds irrespective of the technique used, with the optimal results obtained at intermediate levels (10.5 and 21 min for MAE and UAE, respectively). On the contrary, the only S/L factor was not always significant, even though higher amount of polyphenols were generally recovered at low solid/liquid ratio (0.05 and 0.07 g/mL for MAE and UAE, respectively). Finally, UAE extracts exhibited higher content of anthocyanins, procyanidins, flavonols, and stilbenes than MAE, with values ranging from 1.5 to 69.6 mg/100 g of fresh weight