Validation of green‐solvent extraction combined with chromatographic chemical fingerprint to evaluate quality of Stevia rebaudiana Bertoni

An approach that combined green‐solvent methods of extraction with chromatographic chemical fingerprint and pattern recognition tools such as principal component analysis (PCA) was used to evaluate the quality of medicinal plants. Pressurized hot water extraction (PHWE) and microwave‐assisted extraction (MAE) were used and their extraction efficiencies to extract two bioactive compounds, namely stevioside (SV) and rebaudioside A (RA), from Stevia rebaudiana Bertoni (SB) under different cultivation conditions were compared. The proposed methods showed that SV and RA could be extracted from SB using pure water under optimized conditions. The extraction efficiency of the methods was observed to be higher or comparable to heating under reflux with water. The method precision (RSD, n = 6) was found to vary from 1.91 to 2.86% for the two different methods on different days. Compared to PHWE, MAE has higher extraction efficiency with shorter extraction time. MAE was also found to extract more chemical constituents and provide distinctive chemical fingerprints for quality control purposes. Thus, a combination of MAE with chromatographic chemical fingerprints and PCA provided a simple and rapid approach for the comparison and classification of medicinal plants from different growth conditions. Hence, the current work highlighted the importance of extraction method in chemical fingerprinting for the classification of medicinal plants from different cultivation conditions with the aid of pattern recognition tools used.     

The evolution model of the rayleigh-taylor instability development

The turbulent mixing (TM) of different DT-fuel areas (cold with hot) and of DT-fuel with ablator is one of the deciding factors, determining the neutron yield from compressing laser fusion, and, more generally, inertial confinement fusion (ICF) targets. A lower than predicted neutron yield gained in experiments is not studied comprehensively, but can be caused by the mixing processes. A study of mixing in the ICF problem is complicated by density gradients, spherical convergence, compression, etc., so we suppose the fundamental understanding of the mixing processes must be acquired first in the problem of classical Rayleigh-Taylor (RT) instability in plain geometry. In our work we present results, obtained by the supercomputer numerical modeling of RT-induced TM processes with different initial conditions in 2D and 3D geometries conditions on a high-resolution meshes. For analysis of the modeling results we use an evolutionary model of singular perturbation development, including linear and non-linear stages. This theoretical approach allows us to obtain highly detailed view of the mixing zone evolution along with possibility to trace the initial conditions influence on the mixing late stages.     

Effects of poloxamer on the gelation of silk fibroin

The influence of the concentration of poloxamer 407, the pH and the temperature on the gelation of silk fibroin (SF) were studied. It was found that the gelation of SF occurred in the presence of poloxamer at pH value of 7.0 while gelation of SF itself did not occur. The gelation time of SF was shortened with increasing the poloxamer concentration and the temperature. The sol‐gel transition of SF became reversible with an addition of poloxamer. From infrared (IR) and circular‐dichroism (CD) spectroscopy measurements, it was found that a conformational change of the SF in the SF/poloxamer system from random coil to β‐structure was accelerated after forming a polymer complex with the poloxamer. The crystallinity of the poloxamer was reduced by SF from X‐ray diffraction measurements.