Separation and determination of podophyllum lignans by micellar electrokinetic chromatography

A micellar electrokinetic chromatography method was established for the quantitative analysis of seven podophyllum lignans in Podophyllum emodi Wall. var. chinesis sprague. The optimum buffer system was 10 mM NaH2PO4-5 mM borate-100 mM sodium dodecylsulfate-30% isopropanol (pH 7.20). Voltage was 18 kV and detection at 214 nm. The second derivative chromatogram was used to determine a low-content component and those not fully separated from adjacent ones. The RSD values of migration times and peak areas were <2.2 and <5.5%, respectively. The effects of several CE parameters on the resolutions were studied systematically.     

Separation of gallic acid from Cornus officinalis Sieb. et Zucc by high-speed counter-current chromatography

Gallic acid was separated from a n-butanol extract of the fruit of Cornus officinalis Sieb. et Zucc by high-speed countercurrent chromatography in two steps using two solvent systems composed of ethyl-acetate-ethanol n-butanol-water (5:1.8:6, v/v/v) and ethyl acetate-ethanol-water (5:0.5:6, v/v/v) successively. From 1 g of n-butanol extract the method produced 60 mg of gallic acid at a purity of 97%.     

Spectrophotometric determination of thorium in food using 2-(2,5-disulfonic-4-methoxyphenylazo)-7-(2-hydroxyl-5-carboxylphenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid

A new highly sensitive and selective chromogenic reagent, 2-(2,5-disulfonic-4-methoxyphenylazo)-7-(2-hydroxyl-5-carboxylphenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid (1), was synthesized and applied to the spectrophotometric determination of trace thorium. In 5 mL of a 6 M perchloric acid medium, which greatly increases the selectivity, thorium reacts with 1 to form a 1: 2 green complex, having a sensitive absorption peak at 670 nm. Under optimal conditions, Beer’s law is obeyed over the range from 0 to 0.8 μg/mL Th(IV) and the apparent molar absorptivity is 2.09 × 10⁵ L/mol cm. It is found that, uranium(VI), Ti(IV), heavy rare earths, and most of other common metal ions do not interfere. The method has been tested on the determination of thorium in food samples with satisfactory results. The text was submitted by the authors in English.     

Study of the Fluorescence System of Europium–Enoxacin and its Applications

 This paper is the study of the fluorescence enhancement of Eu³⁺-1-ethyl-6-fluoro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridin-3-carbonic acid (enoxacin, EFLX) system by surfactants. It was found that sodium dodecylbenzenesulfonate (SDBS) exhibits great enhancement on the fluorescence of the Eu-EFLX system. The molar ratio is 1:2:1 for Eu:EFLX: SDBS. Under the optimum conditions, the fluorescence intensity is a linear function of europium in the range of 1.0 × 10⁻⁸ ∼ 5.0 × 10⁻⁶ mol/L, the detection limit is 1.0 × 10⁻⁹ mol/L. The application of the Eu-EFLX-SDBS system for the determination of trace europium in rare earth samples gave satisfactory results. Received October 19, 2000. Revision August 10, 2001.     

Simultaneous determination of noradrenaline and dopamine in Portulaca oleracea L. by capillary zone electrophoresis

A simple and rapid capillary electrophoretic method was developed for the simultaneous determination of noradrenaline (NA) and dopamine (DA) in Portulaca oleracea L. The buffer solution used in this method was 40 mM tris (hydroxymethyl) aminomethane (Tris)-H3PO4 at pH 2.00 containing 15% methanol. The effects of pH value, organic modifier, and applied voltage were investigated. The linear ranges of NA and DA were 0.5-100 microg/mL (r=0.9952) and 6.25-200 microg/mL (r=0.9992), respectively. The relative standard deviations of the corrected peak area were 6.73% and 4.26%, respectively. NA and DA in Portulaca oleracea L. were simultaneous determined successfully within 5.6 min. In this way, the contents of NA and DA in different parts (stem, leaves, and seeds) of P. oleracea L. and in different extracts of leaves with different solvents (distilled water, 50% methanol, and methanol) were studied.     

Duality and intersection theory in complex manifolds. I

We introduce the concept of a twisting cochain and a twisted complex associated to a coherent sheaf. For sheaves of submanifolds these twisted complexes are used to construct on cochain level the Grothendieck theory of dual class and Gysin map. These explicit constructions give, for instance, a local formula for dual class of higher codimensional submanifolds. We prove a refined version of the Hirzebruch Riemann Roch using such local formulas. We also prove a theorem on when global analytic intersection classes can be computed from first order geometric data. This theory will be used to prove the Holomorphic Lefschetz formula (in Part II) and the Hirzebruch Riemann Roch for analytic coherent sheaves.The first author is supported in part by NSF grants GP-36418X1 and MCS 76-08478. The second by MCS 75-07986 and Sonderforschungsbereich Theoretische Mathematik at Bonn University     

Mimicking primary processes in photosynthesis—covalently linked porphyrin quinones

Porphyrin quinones (P-Qs), covalently linked via different aliphatic bridges, have been synthesized and studies in their (porphyrin) cationic and (semiquinone) anionic radical states by EPR, ENDOR and TRIPLE resonance techniques. Electron transfer (ET) from the porphyrin donor to the quinone acceptor could be observed by time-resolved picosecond fluorescence spectroscopy (singlet ET) and by time-resolved EPR spectroscopy (triplet ET) in isotropic fluid solution and in anisotropic media (liquid crystals and reversed micelles). Steady-state in situ photoexcitation of P-Qs in CTAB cationic reversed micelles yielded the corresponding semiquinone radical anions. In TRITON X-100 reversed micelles both the radical cation of the porphyrin and the radical anion of the semiquinone could be detected, which occured in complete emission. In covalently linked porphyrin flavins ET from the photoexcited porphyrin fragment to the flavin and, in addition, energy transfer from the photoexcited flavin to the porphyrin could be observed.     

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.     

New Nitrogenous Bisabolene‐Type Sesquiterpenes from a Hainan Sponge Axinyssa aff. variabilis

Two new uncommon nitrogenous sesquiterpenes, 11‐ethoxy‐3‐formamidotheonellin ( 1 ) and 7‐ethoxy‐3‐formamidobisabolane‐8,10‐diene ( 2 ), together with two known related sesquiterpenes, 3‐formamidotheonellin (=theonellin formamide; 3 ) and theonellin isothiocyanate ( 4 ), were isolated from the Hainan sponge Axinyssa aff. variabilis. Their structures were determined on the basis of extensive spectroscopic analysis and by comparison of their NMR data with those of known compounds.     

Application of preparative high-speed counter-current chromatography for separation of methyl gallate from Acer truncatum Bunge

Preparative separation of methyl gallate in leaves extract of Acer truncatum Bunge was conducted using high-speed counter-current chromatography (HSCCC) with a solvent system composed of ethyl acetate-ethanol-water at volume ratios of 5:1:5 (v/v/v). In a single operation, 57.5 mg of methyl gallate was obtained from 120 mg of the extract. HPLC analyses of the counter-current chromatography (CCC) fraction revealed that the methyl gallate was having over 97% purity. Its structure was identified by 1H NMR and 13C NMR.