A rapid and sensitive ultrahigh-performance liquid chromatography-tandem mass spectrometry method was developed and validated for simultaneous determination of 15 bioactive ingredients in rat plasma and tissues after oral administration of Polygonum chinense Linn extract (PCE). After addition of internal standards (ISs; rutin and danshensu), plasma and tissue samples were pre-treated by protein precipitation with acetonitrile-ethanol. The chromatographic separation was performed on an Agilent ZORBAX RRHD Eclipse Plus C18 column with gradient elution using a mobile phase composed of methanol and water (containing 0.2% acetic acid) at a flow rate of 0.3 mL min-1 . Mass spectrometric detection was carried out using a mass spectrometer in both positive and negative ion electrospray ionization modes by multiple reaction monitoring. The method provided excellent linearity, and the lower limit of quantification range 0.5-30 ng mL-1 for all analytes. The intra- and inter-day precision were less than 9.12% and the accuracy ranged from -4.02% to 6.32%, respectively. The mean extraction recovery and matrix effect of analytes and ISs ranged from 83.65% to 109.20%. The method was successfully applied to the pharmacokinetics and tissue distribution study of 15 ingredients of PCE in rats.

A rapid and sensitive ultra high performance liquid chromatography with tandem mass spectrometry method was established and validated for simultaneous determination of thirteen bioactive components (gallic acid, protocatechuic acid, puerarin, p-hydroxycinnamic acid, daidzin, ononin, daidzein, naringenin, genistein, apigenin, formononetin, biochanin A, and beta-sitosterol) of Radix Puerariae extract in rat plasma and tissues. The plasma and tissues samples were pretreated by protein precipitation extraction, and umbelliferone and rutin were used as internal standards. Sample separation was performed on a ZORBAX RRHD Eclipse plus C-18 column (2.1 mm x 50 mm, 1.8 mu m, Agilent) with a mobile phase consisting of methanol-water (containing 0.1% formic acid). The mass spectrometry analysis was conducted in positive and negative ionization modes with multiple reaction monitoring. The lower limit of quantitation range for the 13 analytes was 0.2-35 ng/mL. The intra- and inter-day precision of all the analytes were less than 10.92%, with an accuracy ranging from -13.10 to 11.96%. Both the recovery and matrix effect were within acceptable limits. This method was successfully applied to pharmacokinetic and tissue distribution study of the 13 bioactive components in rats after oral administration of R. Puerariae extract.

A rapid, sensitive and selective ultra high-performance liquid chromatography-tandem mass spectrometry UHPLC-MS/MS method has been developed and validated for the simultaneous determination of fourteen bioactive ingredients (gallic acid, geniposidic acid, protocatechuic acid, caffeic acid, ferulic acid, scopoletin, apigenin-7-o-glucuronide, daidzein, apigenin, ursolic acid, oleanolic acid, B-sitosterol, coniferin, and stigmasterol) in the plasma and tissues of rats. Danshensu and icariin were used as internal standards (IS1 and IS2). The chromatographic separation was achieved by using an Agilent ZORBAX RRHD Eclipse Plus C18 column (2.1 mm x 50 mm, 1.8 mu m) with gradient elution using mobile phase, which consisted of 0.1% acetic acid water (solvent A) and methanol (solvent B) and pumped at a flow rate of 0.3 mL/min. Mass spectrometric detection was performed in multiple reaction monitoring (MRM) mode utilizing electrospray ionization (ESI) in positive and negative mode. The plasma samples were pretreated via protein precipitation with 300 pi of methanol containing 0.1% (v/v) formic acid and organ homogenates were processed by solid-phase extraction (SPE) with Waters Oasis HLB 3 cc (60 mg), respectively. The intra- and inter- day precisions (RSD%) were less than 10.3%, while the accuracy was ranged from -7.34% to 9.10%. Extraction recovery ranged from 85.02 to 112.0% and the matrix effects ranged from 85.12% to 109.6%. The present method exhibited excellent linearity and the lower limits of quantification (LLOQ) were 30.0 ng/mL, 15.0 ng/mL, 80.0 ng/mL, 30.0 ng/mL, 10.0 ng/mL, 3.0 ng/mL, 2.5 ng/mL, 2.5 ng/mL, 1.5 ng/mL, 15.0 ng/mL, 75.0 ng/mL, 15.0 ng/mL, 30.0 ng/mL, and 20.0 ng/mL for gallic acid, protocatechuic acid, geniposidic acid, caffeic acid, ferulic acid, scopoletin, apigenin-7-o-glucuronide, daidzein, apigenin, ursolic acid, oleanolic acid, beta-sitosterol, coniferin, and stigmasterol, respectively. This analytical method was verified by the FDA guidelines for bioanalytical method validation and applied to investigate the pharmacokinetics and biodistribution of fourteen constituents of Hedyotis diffusa Willd extract in rats. These results provide useful information for improving the pharmacokinetics and biodistribution of fourteen bioactive ingredients of Hedyotis diffusa Willd extract in SD rats, supporting additional clinical application and Chinese herbal medicine safety evaluations. (C) 2018 Elsevier B.V. All rights reserved.

AbstractThe crystal and electronic structure of the title compound is investigated by first principle DFT calculations.

Surface energy,surface relaxation and electronic structure of(10-10)and(0001)surface for calcite CaCO3 were systematically studied using first-principles calculations with slab-model. Results demonstrate that(0001)surface has higher surface energy,thus less stable and grows faster than(10-10)surface which is thus easy to be exposed due to lower surface energy.After surface relaxation,Ca and C atoms in(10-10)surface contract inwards while O atoms expand outwards slightly.Rotation of surface CO2-3 groups results in more stable structure.Ca,C and O atoms of(0001)surface contract inwards and relaxation degree is higher than that of(10-10)surface.DOS indicates that bulk CaCO3 has a band-gap of about 5.0eV,while band-gap of surface structure narrows and(0001)surface has the narrowest band-gap value.C-O bonding is stronger than Ca-O bonding,both C-O and Ca-O bondings in(0001)surface are relatively weak.Surface stability is closely related to O-p electrons.Charge density shows that three C-O bondings in(0001)plane form triangular CO2-3 group.C-O and Ca-O bondings in(10-10)surface are stronger than that in(0001)surface,and charge density of(10~10)surface is also higher,thus(10-10)surface is more stable.

The H coordinates are predicted for LiCa(AlH4)3 in which Li–H bonding and Ca–H anti-bonding interactions are illustrated.

A comparative study of single- and co-substitution of Ti on dehydrogenation of Mg2NiH4 has been carried out from first-principles calculations based on density functional theory. In comparison with Ti single-substitution, the formation enthalpy in co-substituted Mg2NiH4 is higher, showing the lower thermodynamic stability. In Ti co-doped Mg2NiH4, the average NiH bond length of entire unit cell is larger, implying weaker NiH bonds and lower stability of complexes NiH44−. Ti co-substitution further shows a more favorable dehydrogenation effect on Mg2NiH4 due to lower hydrogen dehydrogenation energy, and significantly reduces the dehydrogenation reaction enthalpy of Mg2NiH4 by about 30% compared to the pure state. Further calculated electronic structure demonstrates that the co-substituted Mg2NiH4 displays a metallic behavior with the Fermi level locating at the doping band, and the underlying mechanism for improving dehydrogenation properties of co-substituted Mg2NiH4 can be attributed to the weakened NiH interactions together with the narrowed energy gap.

[目的]对氧化钙(100)、(110)和Ca-terminated(111)的表面能、表面弛豫及电子结构进行系统研究.[方法]运用基于密度泛函理论的第一性原理计算体系的表面性能,计算过程采用6层原子和15 A真空层的Slab模型.[结果]计算得到的氧化钙体相晶格常数合理地符合实验值.氧化钙(100)面的表面能最低因而最稳定,更容易暴露.(110)面表面能介于(100)和Ca-terminated (111)面之间,Ca-terminated(111)面的表面能最高而最不稳定.(100)表面弛豫程度最弱,Ca-terminated(111)表面弛豫程度最明显,而(110)表面弛豫程度则介于(100)和Ca-terminated (111)面之间.(100)表面Ca-O和Ca Ca之间的电子云强烈重叠,共价成键特征突出,稳定性高.Ca-terminated (111)表面只存在Ca-Ca原子间电子云重叠,且杂化程度明显变弱,因此Ca-terminated (111)面的稳定性最低,(110)面的稳定性居于(100)面与Ca-terminated(111)面之间.[结论]氧化钙中(100)面的表面稳定性能最好,(110)面次之,Ca-terminated(111)面稳定性最差.

The structural evolution and electronic mechanism for KBH4 phase transition have been systematically investigated using first-principles calculations. The present results demonstrate experimentally observed stability order of α-KBH4>β-KBH4>γ-KBH4, and the predicted transition pressure at 0K for cubic→tetragonal→orthorhombic phase transformation agrees reasonably with experimental measure. The atomic process indicates that KBH4 structural evolution is closely related to rotation and deformation of [BH4]− clusters as well as shift of [BH4]− clusters and K atoms. Along with phase transformation, the band gap of KBH4 narrows, the BH covalent bond weakens while KH interaction enhances, the KK anti-bonding and coulomb repulsion are also stronger.

First-principles calculations based on density functional theory (DFT) were performed to study the destabilizing mechanism of co-doped MgH2 with Al and Y. From the minimization of total electronic energy, the preferential positions of dopants are determined. The calculated formation enthalpy and substitution enthalpy show that incorporation of Al combined with Y atoms into MgH2 is energetically favorable relative to Al doping alone. Due to strong interaction of the dopant Y with Mg and Al, the hydrogen dissociation energy and the dehydrogenation enthalpy are both reduced, indicating that the synergetic effect of Al and Y on destabilizing the MgH2 is superior to that of Al doping. The electronic structures show that the breakage of Mg–H bond is much easier in co-doped case, because of the conduction band shift below the Fermi level and the hybridization of dopants with Mg atoms, which effectively decrease the hybridization between Mg and H.

The Cu-doping effects on dehydrogenation of MgH2 (001) and (110) surfaces were investigated by using first-principles calculations. On the basis of the calculation results of total energy, the Cu dopant prefers to occupy the interstitial site on both surfaces rather than substitute a Mg atom, and the Cu dopant bonds with four adjacent H ions to form a CuH4 cluster. The electronic structures show that Cu Mg and Cu H interactions strongly weaken Mg H interactions, which leads to a reasonable expectation of decreased dehydrogenation temperature. The kinetic barriers for Cu-doped (001) and (110) surfaces are, respectively, reduced to 1.83 and 1.48 eV, showing that improved kinetics can be expected due to the much lower desorption barriers on both Cu-doped surfaces. The present results are beneficial to resolve the disputes between previous reports on the catalytic effects of Cu-doping in the MgH2 system.

Stacking fault energies (SFEs) of Mg solid solutions at different temperatures are very significant for studying dissociation of dislocation, plasticity deformation and other mechanical properties. Our present work starts with the investigation of interactions between basal stacking faults (SFs) and solutes (Li, Cu, Zn, Al, Y and Zr) using first-principles calculations. It is found that the interactions between basal SFs and solutes can be extended to several closed-packed layers. Combined with Fermi-Dirac function of solute distribution at each layer, the temperature dependence of SFE for Mg-X(X = Li, Cu, Zn, Al, Y and Zr) solid solution has been investigated. This study predicts correctly the increase tendency observed in experiment. Then the SFEs of Mg solid solutions at room temperature of 300 K are investigated at different solute concentrations; the obtained concentration dependence of SFEs is in agreement with the available experimental values. So the solute distribution under finite temperature due to the basal SF-solute interactions plays a critical role in the variation of SFEs of Mg solid solutions.

Theoretical study of structural stability and elastic properties of α- and β-MgPd3 intermetallic compounds as well as their hydrides have been carried out based on density functional theory. The results indicate α-MgPd3 is more stable than β phase with increased stability in their hydrides. The calculated elastic constants of α-MgPd3 are overall larger than β phase. After hydrogenation, the elastic constants are enlarged. And the elastic moduli exhibit similar tendency. The anisotropy of α-MgPd3 is larger than β phase, and the hydrides demonstrate larger anisotropy. Their ductility follows the order of α-MgPd3H0.5 < α-MgPd3 < β-MgPd3H < β-MgPd3. Compared with β phase, higher Debye temperature of α-MgPd3 implies stronger covalent interaction, and the Debye temperature of hydrides increases slightly. The electronic structures demonstrate that the Pd–Pd interaction is stronger than Pd–Mg, and Pd–H bonds play a significant role in the phase stability and elastic properties of hydrides.