Solvation Free Energy for Selection of an Aqueous Two-Phase System: Case in Paeonol Extraction from Cortex Moutan.

Aqueous two-phase system(s) (ATPS) has/have been widely employed in the extraction and separation of bioactive molecules from herbs due to its various advantages such as high efficiency and good selectivity. For selecting the type and amount of organics and salts in ATPS, onerous experimental trials are required to ensure the reliability. We intended to develop a theoretical method to select ATPS in the case of paeonol extraction from cortex moutan. The solvation free energies (E solv) of paeonol in the top phase of 54 ATPS (ATPS-acetone, ATPS-acetone-EA, ATPS-THF, ATPS-THF-EA, ATPS-EtOH, and ATPS-EtOH-EA) were calculated with Gaussian 09, and the extraction yields with 54 ATPS were determined. By comparison of E solv and yield, the E solv rank was effective to select the optimal organic type and organic solvent fraction and aqueous salt concentration. With each series of 18 ATPS (ATPS-acetone plus ATPS-acetone-EA; ATPS-THF plus ATPS-THF-EA; or ATPS-EtOH plus ATPS-EtOH-EA), the paeonol yield was correlated with E solv, suggesting that the optimal organic type and fraction and the aqueous NaH2PO4 concentration could be selected by using theoretical E solv, or at least, the theoretical E solv rank could offer effective guidance for experimental design, and thus, tedious and onerous experimental work for optimization in ATPS extraction can be significantly reduced.

Preparation of magnetic metal-organic framework MIL-101(Fe) and its application in the extraction of anthraquinones in rhubarb.

In this work, a magnetic octahedral metal-organic framework (Fe3 O4 @NH2 -MIL-101(Fe)) was synthesized for the magnetic solid-phase extraction of three anthraquinones, including aloe-emodin, emodin, and physcion, in rhubarb. The Fe3 O4 @NH2 -MIL-101(Fe) exhibits a high specific surface area of 259.2 m2 /g with an average pore size of 6.0 nm and high magnetic responsivity of 23.4 emu/g, which may be used as an adsorbent for rapid preconcentration and separation of target analytes. The main parameters for magnetic solid-phase extraction of anthraquinones, including the amount of adsorbent, extraction time, extraction temperature, extraction pH, elution solvent, and elution time, were systematically optimized. The whole extraction process requires a very low amount of adsorbent and a small volume of the sample. Besides, under the optimized conditions, the method shows satisfactory spiked recovery for anthraquinones in the range of 93.3-109.1% and the limits of detection are 1.7-3.4 ng/mL. The relative standard deviations for intra- and inter-day precision are 0.2-1.3% and 0.2-0.6%, respectively. The experimental results indicate that the developed method is feasible for the analysis of anthraquinones in rhubarb.

Preparation and mechanism of hydroxyapatite hollow microspheres with different surface charge by biomimetic method.

To meet the different application requirements in various fields, hydroxyapatite (HA) hollow microspheres with different surface charge were synthesized successfully by biomimetic method using Ca(NO3)2·4H2O and (NH4)2HPO4 in the presence of polyethylene glycol (PEG). Scanning electron microscopy (SEM), High-resolution TEM (HRTEM), X-ray powder diffraction (XRD), and Zeta PALS were used to characterize the obtained samples. The results indicated that the concentration of PEG and temperature significantly affect the morphology of the obtained samples. After incubation for 5 d, the HA hollow microspheres with positive surface charge, HA spherical nanoparticles with surface charge close to zero and calcium deficiency HA (d-HA) hollow microspheres with negative surface charge were obtained respectively in the presence of 5% PEG, 6% PEG and 7% PEG at 15 °C. Brunauer-Emmett-Teller (BET) revealed that the specific surface area of HA hollow microspheres reached 98.50 m2/g, while that of HA spherical nanoparticles were only 4.12 m2/g, hollow microspheres show a better application prospect. The possible formation mechanism was also discussed. Ca/P molar ratio >1.67, the surface charge of HA hollow microspheres inclines to be positive. Ca/P molar ratio <1.67, the surface charge of d-HA hollow microspheres tends to be negative.

Substrates for Paraoxonase.

BACKGROUND: Paraoxonase (PON) is a family of calcium-dependent hydrolases, which is related to many diseases. Elucidation of PON physiological roles, active center and all applications in medical fields are dependent on its substrates. OBJECTIVE: The reports about PON substrates scattered in a long span of period are collected to afford clue for drug design, diagnosis of PON status and other academic purposes. METHOD: PON substrates from 133 references are classified and compared. Structurally, PON substrates are generally classified as organic phosphorous esters, lactones and arylesters. Some phosphoramidates, organophosphorous obidoximes, aryl carboxylic acid amides and special fatty alcohol esters as PON substrates are also included. RESULTS: The electron nature, steric hindrance and hydrophilicity of substrate substituents affecting the PON catalytic ability, binding ability and specificities are discussed. Drugs, prodrugs and naturally endogenous molecules in life processes activated or inactivate by PON are reviewed. Interestingly, some organophosphate and lactone substrates are preferably hydrolyzed by one of the PON1R192Q allozymes, and such a substrate is generally essential for differentiating the three PON1192R phenotypes by using a dual-substrate method. Intricately, some chiral substrates are hydrolyzed by PON stereoselectively. CONCLUSION: As more substrates are synthesized and characterized, more facts about PON structure and catalytic properties (including PON active center and catalytic mechanism) will be revealed, and therefore the use of PON as a drug target or as an accurate disease marker will be achieved.

New chemiluminescent substrates of paraoxonase 1 with improved specificity: synthesis and properties.

Paraoxonase 1 (PON1) is an important hydrolase, and the enzyme activity decreases in patients with liver disease, diabetes, coronary heart disease, etc. Phenyl acetate and organophosphates are usually employed as substrates for serum PON1 activity assay. However, phenyl acetate for arylesterase activity assay exhibits disadvantage of high background. According to properties of PON1, four new chemiluminescent acridinium esters were designed, prepared through three steps, and characterized with (1)H NMR and mass spectrometry (MS) data, and their properties as PON1 substrates were investigated. The hydrolyses of the four compounds catalyzed by recombinant human PON1 (rhPON1) (or serum) followed first-order kinetics within 22 min. The PON1 activator (NaCl, 0.10 mol L(-1)) could boost the rhPON1-mediated and serum-mediated hydrolyses of the acridinium esters to 2.01 ~ 2.26 folds, but 1.0 mol L(-1) NaCl decreased the serum arylesterase activity. RhPON1 showed selectivity over other serum esterases such as lipase, acetylcholinesterase, and esterase D more than 300 folds. By using ethylene diamine tetraacetic acid (EDTA) inhibitor, the specificities of the four substrates toward serum PON1 were determined as 78.3 ~ 92.9%, which is improved than that of the model compound 9-(4-chloro-phenoxycarbonyl)-10-methylacridinium ester triflate. Due to low toxicity, high specificity, and sensitivity of the substrates, they are useful for serum PON1 activity assay.