Crystallization of Asiaticoside from Total Triterpenoid Saponins of <i>Centella Asiatica</i> in a Methanol + Water System

In this contribution, a novel solvent system for the crystallization of asiaticoside from total triterpenoid saponins of <i>Centella asiatica</i> was established by utilizing the difference between the induction periods of madecassoside and asiaticoside. Asiaticoside could be separated from the mixture of asiaticoside and madecassoside by crystallization with about 80% yield and 95% purity. The mechanism behind the significantly different induction periods of asiaticoside and madecassoside in the methanol + water system is also proposed. Crystallization of asiaticoside from total triterpenoid saponins of <i>Centella asiatica</i> achieved a maximum yield of 60% with 70% purity. A recrystallization was carried out to obtain 76% yield with 91% purity. The optimized conditions for the crystallization of asiaticoside from total triterpenoid saponins of <i>Centella asiatica</i> were determined

Kinetics and Mechanism of Hydrothermal Decomposition of Lignin Model Compounds

The kinetics and underlying mechanisms of the hydrothermal decomposition of the lignin model compounds anisole, diphenyl ether and phenethyl phenyl ether were studied. Whereas diphenyl ether was stable at hydrothermal conditions, anisole and phenethyl phenyl ether underwent hydrothermal decomposition between 260 and 290 °C. Experiments involving different initial reactant concentrations and different batch holding times revealed that hydrolysis of both anisole and phenethyl phenyl ether followed first-order kinetics. Experiments at different temperatures showed that the first-order rate constants displayed Arrhenius behavior, with activation energies of 149.8 ± 16.4 and 143.2 ± 21.0 kJ·mol^–1 for anisole and phenethyl phenyl ether, respectively. A reaction mechanism is proposed for anisole, and reaction pathways for the decomposition of phenethyl phenyl ether are proposed based on the distribution of the products generated by hydrolysis. The reactivity of ether hydrothermal decomposition is discussed by reviewing the published conversion data of other ethers

Robust optimal policies for Markov decision processes with safety-threshold constraints

Abstract: We study the synthesis of robust optimal control policies for Markov decision processes with transition uncertainty (UMDPs) and subject to two types of constraints: (i) constraints on the worst-case, maximal total cost and (ii) safety-threshold constraints that bound the worst-case probability of visiting a set of error states. For maximal total cost constraints, we propose a state-augmentation method and a two-step synthesis algorithm to generate deterministic, memoryless optimal policies given the reward to be maximized. For safety threshold constraints, we introduce a new cost function and provide an approximately optimal solution by a reduction to an uncertain Markov decision process under a maximal total cost constraint. The safety-threshold constraints require memory and randomization for optimality. We discuss the use and the limitations of the proposed solution

Microwave-Assisted Oxidative Degradation of Lignin Model Compounds with Metal Salts

A systematic study on microwave-assisted oxidative degradation of lignin model compounds, such as 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol, was performed by evaluating the catalytic activity of 14 types of metal salts. The acidity of each metal salt solution for the oxidative degradation of 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol under the microwave irradiation and conventional heating conditions was measured and compared. The results showed that CrCl₃ and MnCl₂ were the most effective for the degradation of the lignin model compounds. The acidity of metal salt is in favor of the catalytic activity for the degradation of 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol, and microwave irradiation is able to accelerate the degradation rate in a large scale. The possible mechanisms for the degradation of 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol are proposed on the basis of the product distributions

Additional file 1 of Nanoparticle delivery of TFOs is a novel targeted therapy for HER2 amplified breast cancer

Additional file 1

Copper-Catalyzed Decarboxylation of 2,4,5-Trifluorobenzoic Acid in NH₃‑Enriched High-Temperature Liquid Water

1,2,4-Trifluorobenzene, the decarboxylation product of 2,4,5-trifluorobenzoic acid, is an important raw material for synthesizing sitagliptin phosphate, the main medicinal treatment for diabetes. The traditional synthesis suffers from environmental concerns; therefore, in this work, a series of metal catalysts was employed to catalyze the decarboxylation of 2,4,5-trifluorbenzoic acid in NH₃-enriched high-temperature liquid water (HTLW) to address these concerns. Copper catalysts exhibited excellent performance, and heterogeneous copper catalysts, such as Cu and Cu₂O, led to a higher yield of 1,2,4-trifluorobenzene (89.1%) than homogeneous copper catalysts, such as CuCl₂ and CuCl. The effects of catalyst loading and reactant loading on the decarboxylation of 2,4,5-trifluorbenzoic acid were also investigated. Increases in the catalyst and reactant loadings were favorable for the decarboxylation of 2,4,5-trifluorbenzoic acid; however, a high catalyst loading was not favorable. A reusability test with Cu₂O revealed that Cu₂O has excellent activity maintenance in NH₃-enriched HTLW

Synergy of Lewis and Brønsted Acids on Catalytic Hydrothermal Decomposition of Hexose to Levulinic Acid

The mixed-acid systems of four Lewis acids (FeCl₃, CrCl₃, ZnCl₂, and CuCl₂) combining three Brønsted acids (H₂SO₄, HCl, and H₃PO₄) were evaluated for the decomposition of glucose to produce levulinic acid (LA). The CrCl₃–H₃PO₄ system had a strong synergic catalytic activity for the decomposition of glucose to LA. The effects of the ratio of CrCl₃ and H₃PO₄ on glucose, fructose, and 5-hydroxymethylfurfural (5-HMF) decompositions were investigated. The mixed-acid system showed the strongest synergic catalytic activity for glucose, fructose, and 5-HMF decompositions when the ratio of CrCl₃ in the CrCl₃–H₃PO₄ system was 0.4–0.5. To probe the synergic catalysis mechanism of the CrCl₃–H₃PO₄ system, the synergic catalytic activities of CrCl₃–phosphates (KH₂PO₄, K₂HPO₄, and K₃PO₄) systems on glucose decomposition were also evaluated. The possible synergic catalysis mechanisms were proposed. This study provides insights for the synergic catalysis mechanism of hexose conversion to yield LA

Effects of Oil and Dispersant on Formation of Marine Oil Snow and Transport of Oil Hydrocarbons

This work explored the formation mechanism of marine oil snow (MOS) and the associated transport of oil hydrocarbons in the presence of a stereotype oil dispersant, Corexit EC9500A. Roller table experiments were carried out to simulate natural marine processes that lead to formation of marine snow. We found that both oil and the dispersant greatly promoted the formation of MOS, and MOS flocs as large as 1.6–2.1 mm (mean diameter) were developed within 3–6 days. Natural suspended solids and indigenous microorganisms play critical roles in the MOS formation. The addition of oil and the dispersant greatly enhanced the bacterial growth and extracellular polymeric substance (EPS) content, resulting in increased flocculation and formation of MOS. The dispersant not only enhanced dissolution of <i>n</i>-alkanes (C9–C40) from oil slicks into the aqueous phase, but facilitated sorption of more oil components onto MOS. The incorporation of oil droplets in MOS resulted in a two-way (rising and sinking) transport of the MOS particles. More lower-molecular-weight (LMW) <i>n</i>-alkanes (C9–C18) were partitioned in MOS than in the aqueous phase in the presence of the dispersant. The information can aid in our understanding of dispersant effects on MOS formation and oil transport following an oil spill event

Spatial and Temporal Confinement of Salt Fluxes for the Shape-Controlled Synthesis of Fe₂O₃ Nanocrystals

Here, molten salt syntheses (MSS) are coupled with ultrasonic spray pyrolysis to yield single-crystalline Fe₂O₃ nano- and microparticles with controlled shapes and phases. It was previously demonstrated that aerosol-assisted MSS can produce single-crystalline nanoplates. Now, by selecting different molten salt flux components, various crystalline phases and particle shapes are accessed via the dissolution of Fe₂O₃ colloids, followed by precipitation of the iron oxide products from molten alkali carbonates that are spatially and temporally confined in the aerosol phase. This confinement limits crystal growth to the nanoscale and provides access to products at different stages of supersaturation. The resulting powders consist of hexagonal nanoplates (α- or γ-Fe₂O₃), rhombohedra (α-Fe₂O₃), or octahedra (LiFe₅O₈) depending on the selected molten salt flux. Significantly, this synthetic approach represents a continuous and potentially general route to the generation of shape- and phase-controlled nano- and microcrystals given the diversity of materials previously prepared by molten salt techniques

Hydrothermal Synthesis of Graphitic Carbon Nitride–Bi₂WO₆ Heterojunctions with Enhanced Visible Light Photocatalytic Activities

Graphitic carbon nitride (C₃N₄) was hybridized by Bi₂WO₆ via a hydrothermal method. The high-resolution transmission electron microscopy (HR-TEM) results reveal that an intimate interface between C₃N₄ and Bi₂WO₆ forms in the heterojunctions. The UV–vis diffuse reflection spectra show that the resulting C₃N₄–Bi₂WO₆ heterojunctions possess more intensive absorption within the visible light range in comparison with pure Bi₂WO₆. These excellent structural and spectral properties endowed the C₃N₄–Bi₂WO₆ heterojunctions with enhanced photocatalytic activities. Significantly, the optimum photocatalytic activity of the 0.5C₃N₄–0.5Bi₂WO₆ heterojunction for the degradation of methyl orange (MO) was almost 3 and 155 times higher than those of either individual C₃N₄ or Bi₂WO₆. The possible photocatalytic mechanism with superoxide radical species as the main active species in photocatalysis is proposed on the basis of experimental results. Moreover, the heterojunction depicted high stability and durability during six successive cycles