<Emphasis Type="Italic">In vitro</Emphasis> inhibitory effect of polyoxometalates on human tumor cells

H₇[NiV₁₃O₃₈] was synthesized from K₇[NiV₁₃O₃₈] using an ion exchange method. Then Pr₂H[NiV₁₃O₃₈] was obtained by double decomposition of H₇[NiV₁₃O₃₈] with Pr₂(CO₃)₃. The actual amount of praseodymium measured by elemental analysis coincides with the designed amount of praseodymium in Pr₂H[NiV₁₃O₃₈]. The i.r. spectra suggested that the [NiV₁₃O₃₈]^7– anion did not collapse after the ion exchange and double decomposition. The ⁵¹V n.m.r. spectrum of Pr₂H[NiV₁₃O₃₈] showed four peaks and their ratio of the relative intensity was 4:4:4:1. This result agrees with the chemical environment of V atoms in the [NiV₁₃O₃₈]^7– anion. In vitro antitumor activities of polyoxometalates on several human tumor cells have been investigated using the MTT method. Pr₂H[NiV₁₃O₃₈] is the most effective polyoxometalate tested in this study for inhibiting KB cell. Pr₂H[NiV₁₃O₃₈] also showed remarkable inhibitory effect on some other tumor cells: HCT, Bel, B₁₆, BCAP and ESCL cells. These results indicate that Pr₂H[NiV₁₃O₃₈] is a potent broad spectrum antitumor agent. The structure type of polyoxometalates greatly influences their antitumor activity: the order of structure type for inhibiting KB cell is: [NiV₁₃O₃₈]^7–>[Mo₇O₂₄]^6–>Anderson structure Keggin structure Dawson structure. Moreover, the nature of the polyatom in the polyoxometalates also greatly influences their antitumor activity: the polyatom order for inhibiting KB cell is: V>Mo W. On the other hand, the nature of the counter cation and the heteroatom in the polyoxometalates exerted a relatively small influence on the inhibitory effect against the KB cell, although the praseodymium salt of [NiV₁₃O₃₈]^7– showed a higher antitumor activity than its potassium salt.     

Synthesis of seven-membered ring diazepin-2-ones via palladium-catalyzed highly regioselective cyclization of 2-vinylpyrrolidines with aryl isocyanates

The first palladium-catalyzed ring-expansion reaction of 2-vinylpyrrolidines with aryl isocyanates to form seven-membered ring heterocycles is described. This regioselective reaction requires 5 mol % of Pd(2)(dba)(3).CHCl(3) and 10 mol % of dppp at 40-60 degrees C in THF and results in the formation of 1,3-diazepin-2-ones in good isolated yields. When Pd(OAc)(2) and PPh(3) were utilized in the reaction, an intramolecular hydrogen migration occurs resulting in the formation of conjugated diene derivatives of urea.     

Influence of organic bases on constructing 3D photoluminescent open metal-organic polymeric frameworks

Four three-dimensional non-interpenetrating open coordination frameworks constructed from the CTC ligand (CTC =cis,cis-1,3,5-cyclohexanetricarboxylate) coordinated to metal ions (Mn(II) and Cd(II)): Mn(3)(CTC)(2)(DMF)(2)(1); Cd(3)(CTC)(2)(H(2)O)(3).H(2)O (2); Cd(3)(CTC)(2)(4,4'-bpy)(2)(EG)(2)(3); Cd(3)(CTC)(2)(mu(2)-hmt)(DMF)(C(2)H(5)OH)(H(2)O).2H(2)O (4)(DMF = dimethylformamide and EG = ethylene glycol) have been synthesized by slow evaporation of DMF-C(2)H(5)OH-H(2)O solutions of M(II)(Mn(II) or Cd(II)) and CTC in the presence of the organic bases TEA (triethylamine), TEA, 4,4'-bpy (4,4'-bipyridine) and hmt (hexamethylenetetramine), respectively, and structurally characterized by X-ray crystallography. The polymer constructed by CTC and Mn(II) exhibits a 3-D architecture with 5 x 9 A channels; the polymer formed by CTC and Cd(II) exists a 3-D extended framework with 9 x 9 A channels; wave-like sheet subunits of the polymer are upheld by 4,4'-bpy ligands resulting in a 3-D framework with 4 x 10 A channels; two-fold alternate sheet subunits of the polymer are interlinked by mu(2)-hmt ligands to form a novel 3-D architecture with 7 x 8 A channels. Polymers exhibit their strongest excitation peaks at 391, 390 and 394 nm, respectively, and their main strong emission peaks are at 543, 460 (with a shoulder peak at about 570 nm) and 557 nm, respectively.     

Simultaneous Determination of Enalapril and Enalaprilat in Human Plasma by LC-MS: Application to a Bioequivalence Study

A rapid, simple and specific liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed and validated for the simultaneous determination of enalapril and its major active metabolite enalaprilat in human plasma. Benazepril hydrochloride was used as the internal standard. Plasma was deproteinized with acetone and centrifuged. The supernatant was transferred and evaporated to dryness and the residue dissolved in mobile phase. Samples were separated on a C18 column with a mobile phase of methanol–20 mM ammonium acetate (53:47, v/v) containing 0.15% trifluoracetic acid (v/v) with a pH of 3.0. Enalapril, enalaprilat and the internal standard were measured by electrospray positive selective ion monitoring mode. The method was validated over a linear range of 1.56–400 ng mL⁻¹ and the limits of quantification were 1.56 ng mL⁻¹ for both enalapril and enalaprilat using 0.1 mL plasma. Extraction efficiency was more than 84% and recoveries were in range of 93.65–101.17%. The intra-day relative standard deviations (RSD) were less than 8.16 and 7.05% and inter-day RSDs were within 8.42 and 5.72% for enalapril and enalaprilat, respectively. The storage stability of QC samples was investigated under various conditions. The method was successfully applied for the evaluation of the pharmacokinetics and bioequivalence of enalapril and enalaprilat in 20 healthy volunteers after an oral dose of 20 mg enalapril maleate.     

Rapid and sensitive determination of ephedrine and pseudoephedrine by micellar electrokinetic chromatography with on-line regenerating covalent coating

A rapid, sensitive and reproducible micellar electrokinetic chromatographic method using hexamethyldisilazane as on-line regenerating covalent coating was developed for the quantification of ephedrine (E) and pseudoephedrine (PE). E and PE were derivatized with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazol for laser-induced fluorescence detection. The on-line regenerating covalent coating formed a combinative double coating with the subsequently produced dynamic SDS coating. The total coating can be easily removed and conveniently regenerated on-line. The simple coating procedure was described. By a series of optimization, a running buffer of 20 mm Na(2)B(4)O(7) + 16 mm SDS was applied for the separation of the derivatives. Linear relationships for E and PE were obtained in the range of 0.044-6.60 microg mL(-1) (correlation coefficients: 0.9975 for E, 0.9981 for PE), and the detection limits for E and PE were 1.71 and 0.67 ng mL(-1), respectively. The separation speed, the reproducibility and the sensitivity were much improved over those of other capillary electrophoresis methods more recently reported. The method was applied to the analysis of the two alkaloids in traditional herbal preparations with recoveries in the range 92.8-104.8%.     

土壤中烃类污染物的超临界流体萃取

采用超临界流体萃取技术提取环境样品中的烃类污染物，以色谱－质谱联用仪测定了萃取物的化学成分，考察了影响萃取效率的主要因素。比传统的索氏萃取能更有效地从复杂环境样品中萃取分析物。     

Biomimetic Asymmetric Reduction of Quinazolinones with Chiral and Regenerable NAD(P)H Models

A facile approach to chiral dihydroquinazolinone derivatives has been described via biomimetic asymmetric reduction of quinazolinones with chiral and regenerable NAD(P)H models. The utility of this method was demonstrated by a concise synthesis of the bromodomain protein divalent inhibitor.     

Synthesis and biodistribution of 99mTcN(PDTC)2as a potential brain imaging agent

The preparation of the bis(N-propyl dithiocarbamato) nitrido technetium-99m complex ^99mTcN(PDTC)₂ (PDTC: N-propyl dithiocarbamato) was carried out as a freeze-dried formulation, through a simple procedure involving the initial of ^99mTcO_4- with succinic dihydrazide in the presence of stannous chloride as reducing agent and propylenediamine tetraacetic acid (PDTA) as complexant, followed by the addition of the ligand sodium salt of N-propyl dithiocarbamate to afford the final product. The radiochemical purity of the complex was over 90%, as measured by thin layer chromatography. No decomposition of the complex at room temperature was observed over a period of 12 hours. Its partition coefficient indicated that it was a good lipophilic complex. Biodistribution in mice showed that the complex accumulated in the brain with high uptake. The brain uptake (ID%/g) was 5.07 and the brain/blood ratio 1.34 at 5-minute post-injection. This suggested a potential usefulness of the complex as a brain perfusion imaging agent. This revised version was published online in July 2006 with corrections to the Cover Date.