Optimization of Extraction of Phenolic Compounds from Flax Shives by Pressurized Low-Polarity Water

Pressurized low-polarity water (PLPW) extraction of phenolic compounds from flax shive was investigated using statistically based optimization and the “one-factor-at-a-time” method. Extraction variables examined using central composite design (CCD) included temperature, flow rate, and NaOH concentration of the extracting water. Extraction of phenolic compounds including p-hydroxybenzaldehyde, vanillic acid, syringic acid, vanillin, acetovanillone, and feruric acid was affected by temperature and NaOH concentration; and extraction of all phenolic compounds, except ferulic acid, increased with temperature and NaOH concentration of the extracting water. Flow rate had little effect on concentration of phenolic compounds at equilibrium, but the extraction rate at the early phase was higher for higher flow rates. The mechanism of PLPW extraction of flax shive phenolics was also investigated using a two-site kinetic model and a thermodynamic model. To determine the extraction mechanism, flow rate was varied from 0.3 to 4.0 mL/min while temperature and NaOH concentration were fixed at 180 °C and 0.47 M, respectively. The flow rate tests showed the extraction rates of total phenolic (TP) compounds increased with flow rate and can be described by a thermodynamic model. The results from the thermodynamic model demonstrated that a KD value of 30 agreed with the experimental data in the flow rate range of 0.3−4.0 mL/min. When the effect of the three independent variables was evaluated simultaneously using CCD, a maximum TP concentration of 5.8 g/kg of dry flax shive (DFS) was predicted from the combination of a high temperature (230.5 °C), a high initial concentration of NaOH (0.63 M), and a low flow rate (0.7 mL/min). Maximum TP concentration of 5.7 g/kg of DFS was obtained from extraction conditions of 180 °C, 0.3 or 0.5 mL/min, and 0.47 M NaOH at equilibrium. A second-order regression model generated by CCD predicted a maximum TP concentration of 5.8 g/kg of DFS under the same extraction conditions, which is well matched with the results from experimental data. Keywords: Phenolics; p-hydroxybenzaldehyde; vanillic acid; vanillin; acetovanillone; ferulic acid; subcritical water; response surface; Linum usitatissimum; lignocellulose; ligni

Mass Transfer during Pressurized Low-Polarity Water Extraction of Phenolics and Carbohydrates from Flax Shives

The effects of pH-buffered water and NaOH solution on pressurized low-polarity water (PLPW) extraction were investigated to determine the optimal conditions for the extraction of lignocellulosic components from flax shives. A high NaOH concentration (0.1 M) and a high pH of buffered water (pH 13) increased the rates of extraction by increasing values of the effective diffusion coefficient (De) from 9.1 × 10-11 m2/s to 1.5 × 10-10 m2/s during PLPW extraction of free phenolic compounds. The concentration of NaOH exerted a significant effect on extraction of free phenolic compounds, whereas PLPW extraction of total carbohydrates was not significantly affected by variation of the pH and NaOH concentration. The maximum concentrations of free phenolic compounds (5.7 g/kg of dry flax shive (DFS)) and total carbohydrates (260 g/kg of DFS) were obtained using 0.1 M NaOH solution and water, respectively, at 230 °C and a flow rate of 2 mL/min. To determine the mechanism that controlled the PLPW extraction of free phenolic compounds and total carbohydrates, the extraction kinetics were studied using a two-site kinetic model and a thermodynamic model. The curves generated using these two models showed good fits to the experimental data within the tested range of flow rate, demonstrating that the extraction mechanism is controlled by both internal diffusion and external elusion. The kinetic values, including the fraction of the analyte released (F) and the kinetic constants obtained from the two-site kinetic model (k1 and k2), increased as the flow rate increased, indicating that the internal diffusion step is not totally independent of the flow rate, because the internal diffusion can be increased by the higher external concentration gradient that is caused by the higher flow rate

Simultaneously Controlled Directionality and Valency on a Water-Soluble Gold Nanoparticle Precursor for Aqueous-Phase Anisotropic Self-Assembly

The anisotropic interaction of gold nanoparticles (AuNP’s) into a highly accurate, scalable complex structure not only would aid practical nanoscale assembly but also would increase their utility in many applications, including electronics, optics, and biosensing. Particularly for biological purposes, here we demonstrate an aqueous-phase serial solid-phase monofunctionalization approach to synthesize water-soluble AuNP linkers that contain distinctive single or double diametric functionalities in a site-specific way. Using a mild, rapid, effective single-phase 1:1 ligand replacement reaction between mixed-ligand-protected AuNP precursors and ligand-group-attached silica gels, we successfully synthesized (1) two types of monofunctionalized (monof-) carboxyl- or amino-AuNP’s with enhanced yield and accuracy and (2) heterobifunctionalized (bif-) AuNP’s with one carboxyl and one amine end group at a discrete angle (∼160°). The controlled coupling chemistry in aqueous solution allowed the covalent bond-directed assembly of intentionally designed 1D dimers with monof-AuNP’s and 2D rings with heterobif-AuNP’s, confirming the highly functional as well as directional selectivity of the functionalized NPs. This study thus represents an important step toward active control over the design and assembly of bottom-up nanostructures with increased complexity and biocompatibility

Sequential Solid-Phase Fabrication of Bifunctional Anchors on Gold Nanoparticles for Controllable and Scalable Nanoscale Structure Assembly

This letter reports a serial solid-phase placement approach to synthesize anisotropically or symmetrically functionalized gold nanoparticles (AuNPs), in which the functionality and directionality (i.e., numbers, locations, and orientations) of the functional ligands are controlled. The solid-phase ligand exchange methodology using highly rigid filter papers enabled us to produce two types of bifunctionalized (bif-) AuNPs in a site-specific manner with increased yield and accuracy: (1) homobif-AuNPs with two carboxyl groups at ∼180° (para configuration) and (2) heterobif-AuNPs with one carboxyl and one amine functional groups at less than 180° but greater than 90° (meta configuration). Their chemical functionality was validated by 1H nuclear magnetic resonance as well as cyclic voltammetry after ferrocene ethylamine coupling reactions. The directional assemblies of 1D chains with homobif-AuNPs and 2D rings with heterobif-AuNPs were demonstrated through diamine and imidization coupling reactions, respectively, further validating their highly functional and directional selectivity, which is critical to realizing the practical nanoscale assembly

Copper Catalyzed Enantioselective Intramolecular Aminooxygenation of Alkenes

Copper Catalyzed Enantioselective Intramolecular Aminooxygenation of Alkene

Copper Catalyzed Enantioselective Intramolecular Aminooxygenation of Alkenes

Copper Catalyzed Enantioselective Intramolecular Aminooxygenation of Alkene

Additional file 1 of Can ultrasonography be used to assess capsular distention in the painful temporomandibular joint?

Additional file 1. Table S1. Questionnaire

Additional file 1 of Association between periodontal disease status and risk of atrial fibrillation: a nationwide population-based cohort study

Additional file 1

Copper Catalyzed Enantioselective Intramolecular Aminooxygenation of Alkenes

Copper Catalyzed Enantioselective Intramolecular Aminooxygenation of Alkene

Additional file 1 of Randomized controlled trial on the effectiveness of absorbable collagen sponge after extraction of impacted mandibular third molar: split-mouth design

Additional file 1: Table S1. Assessment of gingiva recession, gingival index and bleeding on probing