Optimization of green deep eutectic solvent (DES) extraction of Chenopodium quinoa Willd. husks saponins by response surface methodology and their antioxidant activities.

Quinoa saponins have outstanding activity, and there are an increasing number of extraction methods, but there are few research programs on green preparation technology. The extraction conditions of quinoa saponins with deep eutectic solvents (DESs) were optimized by single-factor experiments combined with response surface methodology. The antioxidant capacity of saponins extracted by DESs and traditional methods was evaluated by the DPPH clearance rate, iron ion chelation rate and potassium ferricyanide reducing power. The results show that the optimal DES is choline chloride: 1,2-propylene glycol (1 : 1), and its water content is 40%. The optimal extraction conditions were as follows: the solid-to-solvent ratio was 0.05 g mL-1, the extraction time was 89 min, and the extraction temperature was 75 °C. Under these conditions, the extraction of quinoa saponins by DES was more effective than the traditional extraction methods. The saponins extracted by DES and traditional methods were analyzed by UPLC-MS, and five main saponins were identified. Quantitative analysis by HPLC-UV showed that Q1 (m/z = 971) and Q2 (m/z = 809) had higher contents of saponins. In vitro antioxidant experiments showed that all DES saponin extracts showed good antioxidant capacity. This study provides new insight into the development and utilization of quinoa saponins.

Multifunctional acetylated distarch phosphate based conducting hydrogel with high stretchability, ultralow hysteresis and fast response for wearable strain sensors.

The rapid development of flexible sensors has greatly increased the demand for high-performance hydrogels. However, it remains a challenge to fabricate flexible hydrogel sensors with high stretching, low hysteresis, excellent adhesion, good conductivity, sensing characteristics and bacteriostatic function in a simple way. Herein, a highly conducting double network hydrogel is presented by incorporating lithium chloride (LiCl) into the hydrogel consisting of poly (2-acrylamide-2-methylpropanesulfonic acid/acrylamide/acrylic acid) (3A) network and acetylated distarch phosphate (ADSP). The addition of ADSP not only formed hydrogen bonds with 3A to improve the toughness of the hydrogel but also plays the role of "physical cross-linking" in 3A by "anchoring" the polymer molecular chains together. Tuning the composition of the hydrogel allows the attainment of the best functions, such as high stretchability (∼770 %), ultralow hysteresis (2.2 %, ε = 100 %), excellent electrical conductivity (2.9 S/m), strain sensitivity (GF = 3.0 at 200-500 % strain) and fast response (96 ms). Based on the above performance, the 3A/ADSP/LiCl hydrogel strain sensor can repeatedly and stably detect and monitor large-scale human movements and subtle sensing signals. In addition, the 3A/ADSP/LiCl hydrogel shows a good biocompatibility and bacteriostatic ability. This work provides an effective strategy for constructing the conductive hydrogels for wearable devices and flexible sensors.

Synthesis of Conformationally Liberated Yohimbine Analogues and Evaluation of Cytotoxic Activity.

A modular synthetic approach to strategically unique structural analogues of the alkaloid yohimbine is reported. The overall synthetic strategy couples the transition-metal-catalyzed decarboxylative allylation of 2,2-diphenylglycinate imino esters with a scandium triflate-mediated highly endo-selective intramolecular Diels-Alder (IMDA) cycloaddition to generate a small collection of de-rigidified yohimbine analogues lacking the ethylene linkage between the indole and decahydroisoquinoline units. One compound generated in this study contains an unprecedented pentacyclic urea core and appears to demonstrate increased cytotoxicity against the gastric cancer cell line SGC-7901 in comparison to a pancreatic cancer cell line (PATU-8988) and a normal human gastric mucosal cell line (GES-1).

Less polar ginsenosides have better protective effects on mice infected by Listeria monocytogenes.

Listeria monocytogenes widely exists in the natural environment and does great harm, which can cause worldwide public safety problem. Infection with L. monocytogenes can cause rapid death of Kupffer cell (KCs) in liver tissue and liver damage. American ginseng saponins is a natural compound in plants, which has great potential in inhibiting L. monocytogenes infection. Therefore, American ginseng stem-leaf saponins (AGS) and American ginseng heat-transformed saponins (HTS) were used as raw materials to study their bacteriostatic experiments in vivo and in vitro. In this experiment, female Kunming mice were randomly divided into five groups: control group, negative group, AGS group, HTS group (10 mg/kg/day in an equal volume via gastric administration) and penicillin group, each group containing six mice. Profiles AGS and HTS components were evaluated by high-performance liquid chromatography (HPLC) analysis. The bacteriostatic effect of AGS and HTS on L. monocytogenes was evaluated by inhibition zone test, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The bacteriostatic effect of AGS and HTS pretreatment on mice infected with L. monocytogenes were studies by animal experimental. The results showed that the content of polar saponins in AGS was 0.81 ± 0.003 mg/mg, less polar saponins was 0.08 ± 0.02 mg/mg, the content of polar saponins in HTS was 0.10 ± 0.01 mg/mg, less polar saponins was 0.76 ± 0.02 mg/mg. The in vitro bacteriostatic diameter of HTS (16.6 ± 0.8 mm) is large than that of AGS (10.2 ± 1.2 mm). AGS and HTS pretreatment could reduce the colony numbers in the livers of mice infected with Listeria monocytogenes. The levels of alanine aminotransferase (ALT), IL-1ß, IL-6, TNF-α and IFN-γ in the livers of mice in the pretreatment group were significantly lower than those in the negative group. There were obvious leukoplakia, calcification and other liver damage on the liver surface in the negative control group, and obvious inflammatory cell infiltration in HE sections. AGS and HTS pretreatment can reduce liver injury caused by L. monocytogenes and protect the liver. Compared with AGS, HTS has higher content of less polar saponins and better bacteriostatic effect in vitro. The count of bacterial in liver tissue of HTS group was significantly lower, the survival rate was significantly higher than that of AGS group. Less polar saponins had better bacteriostatic effect. Collectively, less polar saponins pretreatment has a protective effect on mice infected with L. monocytogenes, to which alleviated liver damage, improved anti-inflammatory ability and immunity of the body, protected liver may contribute.

Stem-leaves of Panax as a rich and sustainable source of less-polar ginsenosides: comparison of ginsenosides from Panax ginseng, American ginseng and Panax notoginseng prepared by heating and acid treatment.

BACKGROUND: Ginsenosides, which have strong biological activities, can be divided into polar or less-polar ginsenosides. METHODS: This study evaluated the phytochemical diversity of the saponins in Panax ginseng (PG) root, American ginseng (AG) root, and Panax notoginseng (NG) root; the stem-leaves from Panax ginseng (SPG) root, American ginseng (SAG) root, and Panax notoginseng (SNG) root as well as the saponins obtained following heating and acidification [transformed Panax ginseng (TPG), transformed American ginseng (TAG), transformed Panax notoginseng (TNG), transformed stem-leaves from Panax ginseng (TSPG), transformed stem-leaves from American ginseng (TSAG), and transformed stem-leaves from Panax notoginseng (TSNG)]. The diversity was determined through the simultaneous quantification of the 16 major ginsenosides. RESULTS: The content of ginsenosides in NG was found to be higher than those in AG and PG, and the content in SPG was greater than those in SNG and SAG. After transformation, the contents of polar ginsenosides in the raw saponins decreased, and contents of less-polar compounds increased. TNG had the highest levels of ginsenosides, which is consistent with the transformation of ginseng root. The contents of saponins in the stem-leaves were higher than those in the roots. The transformation rate of SNG was higher than those of the other samples, and the loss ratios of total ginsenosides from NG (6%) and SNG (4%) were the lowest among the tested materials. In addition to the conversion temperature, time, and pH, the crude protein content also affects the conversion to rare saponins. The proteins in Panax notoginseng allowed the highest conversion rate. CONCLUSION: Thus, the industrial preparation of less-polar ginsenosides from SNG is more efficient and cheaper.

Synthesis, characteristics and medical applications of plant nanomaterials.

MAIN CONCLUSION: The recent preparations of metal nanoparticles using plant extracts as reducing agents are summarized here. The synthesis and characterization of plant-metal nanomaterials and the progress in antibacterial and anti-inflammatory medical applications are detailed, providing a new vision for plant-based medical applications. The medical application of plant-metal nanoparticles is becoming a research hotspot. Compared with traditional preparation methods, the synthesis of plant-metal nanoparticles is less toxic and more eco-friendly, increasing application potential. Highly efficient plant-metal nanoparticles are usually smaller than 100 nm. This review describes the synthesis, characterization and bioactivities of gold- and silver-plant nanoparticles as examples and clearly explained their antibacterial and anticancer mechanisms. An analysis of actual cases shows that the synthetic method and type of plant extract affect the activities of the products.

Nickel-Catalyzed Decarboxylative Generation and Asymmetric Allylation of 2-Azaallyl Anions.

The first nickel-catalyzed asymmetric decarboxylative allylation (DcA) of allyl 2,2-diarylglycinate imines is reported. This transformation utilizes a chiral ferrocenyl bidentate ligand and a Ni(0) precatalyst to mediate the decarboxylative generation and asymmetric allylation of 2-azaallyl anions, affording α-aryl homoallylic imines in modest-to-high yields and moderate-to-high enantiomeric ratios. The resulting Ni-catalyzed transformation proved to be less general in comparison to our previously reported analogous Pd-mediated protocol, but it still exhibited certain advantages in regard to the regio- and enantioselectivity of the C-C bond formation.

2-Azaallyl Anions, 2-Azaallyl Cations, 2-Azaallyl Radicals, and Azomethine Ylides.

This review covers the use of 2-azaallyl anions, 2-azaallyl cations, and 2-azaallyl radicals in organic synthesis up through June 2018. Particular attention is paid to both foundational studies and recent advances over the past decade involving semistabilized and nonstabilized 2-azaallyl anions as key intermediates in various carbon-carbon and carbon-heteroatom bond-forming processes. Both transition-metal-catalyzed and transition-metal-free transformations are covered. Azomethine ylides, which have received significant attention elsewhere, are discussed briefly with the primary focus on critical comparisons with 2-azaallyl anions in regard to generation and use.

Decarboxylative Generation of 2-Azaallyl Anions: 2-Iminoalcohols via a Decarboxylative Erlenmeyer Reaction.

Condensation between the tetrabutylammonium salt of 2,2-diphenylglycine and aldehydes results in a decarboxylative Erlenmeyer reaction, affording 1,2-diaryl-2-iminoalcohols as a mixture of diastereomers in good yields. The diastereomeric ratio shifts over time, with the anti diastereomer and the syn oxazolidine tautomer serving as the kinetic and thermodynamic products, respectively. Addition of Lewis acids can catalyze the rates of reaction and product equilibration. The results highlight the stereochemical promiscuity of 1,2-diaryl-2-iminoalcohols in the presence of Lewis acids and Brønsted bases.