An environmentally benign method of sample preparation based on dispersive liquid–liquid microextraction and solidification of floating organic droplets (DLLME-SFO) coupled with high-performance liquid chromatography with ultraviolet detection has been developed for analysis of non-steroidal anti-inflammatory drugs (NSAIDs) in biological fluids. A low-toxicity solvent was used to replace the chlorinated solvents commonly used in conventional DLLME. Seven
conditions were investigated and optimized: type and volume of extraction solvent and dispersive solvent, extraction time, effect of addition of salt, and sample pH. Under the optimum conditions, good linearity was obtained in the range 0.01–10 µg mL−1, with coefficients of determination (r2) >0.9949. Detection limits were in the range 0.0034–0.0052 µg mL−1 with good reproducibility (RSD) and satisfactory inter-day and intra-day recovery (95.7–115.6 %). The method was successfully used for analysis of diclofenac, mefenamic acid, and ketoprofen in human urine. Analysis of urine samples from a patient 2 and 4 h after administration of diclofenac revealed concentrations of 1.20 and 0.34 µg mL−1, respectively.
Isoflavones are a very important group of natural products. This study investigated the separation of eight isoflavones, namely ononin, daidzin, genistin, biochanin A, formononetin, puerarin, genistein, and daidzein, from pueraria by micellar electrokinetic chromatography (MEKC) with different surfactants. The following micellar systems of MEKC were systematically compared for the analysis of these isoflavones: (1) a single surfactant comprising the anionic surfactant sodium dodecyl sulfate (SDS), the cationic surfactant hexadecyltrimethylammonium bromide, the neutral surfactant polyoxyethylene sorbitan monolaurate (Tween 20), and the ionic liquid-type surfactant (also a cationic surfactant) 1-dodecyl-3-methylimidazolium tetrafluoroborate (C12MIMBF4); (2) different single surfactants with 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4) as an additive (modifier); and (3) mixed micelles of SDS + Tween 20 and C12MIMBF4 + Tween 20. Both SDS with BMImBF4 as additive and mixed micelles of SDS + Tween 20 had the highest separation efficiency for the eight investigated compounds. Furthermore, the SDS with BMImBF4 as additive was more stable (good repeatability of retention time and peak shape of analytes) than mixed micelles of SDS + Tween 20, which may be the result of a stabilizing effect of BMImBF4. Therefore, the final analytical conditions were 15 mM SDS added with 50 mM BMImBF4 in 30 mM sodium tetraborate (STB, pH 9.5) as running buffer; applied voltage, 20 kV; injection, 50 mbar for 5 s; cartridge temperature, 25 °C; compounds were detected at 260 nm. The developed method was fully validated (limit of detection, limit of quantification, intraday precision, inter-day precision, and recovery) and successfully applied to determine the eight analytes in three Radix Puerariae samples. The present study indicated that SDS with ionic liquids as additive in MEKC was suitable for the analysis of isoflavones.
4‐Amino‐3‐methyl‐1‐phenyl‐1H‐thieno[2,3‐c]pyrazole‐5‐carboxamide ( 5 ), which was synthesized by an innovative method, was used as a versatile precursor for synthesizing pyrazolothienopyrimidines and imidazopyrazolothienopyrimidines compounds. Reaction of amino thienopyrazole carboxamide 5 with triethyl orthoformate afforded thienopyrazolopyrimidine 6 . Chlorination of the latter compound, using phosphorus oxychloride afforded the chloro pyrazolothienopyrimidine 7 , which underwent nucleophilic substitution reactions with various primary and secondary amines to give the alkyl (aryl) amino pyrimidine compounds 8a–d . On the other hand, the reaction of chloropyrimidine 7 with thiourea afforded the pyrimidine thione compound 9 , which was alkylated with α‐halogentaed compounds to afford the S‐alkylated derivatives 10a–c . Also, chloroacetylation of the amino carboxamide 5 using chloroacetyl chloride yielded the chloromethyl pyrazolothienopyrimidine 12 , which underwent nucleophilic substitu‐ tion reactions with various primary and secondary amines to afford the alkyl (aryl) aminomethyl compounds 13a–f . The latter Compounds underwent Mannich reaction to give imidazopyrimidothieno‐ pyrazoles 14a–c . The newly synthesized compounds and their derivatives were fully characterized by elemental and spectral analysis. 相似文献
Two new eremophilane‐type sesquiterpenoids, 1α‐hydroxyeremophila‐6,9,11‐trien‐8‐one ( 1 ), 4α‐hydroxyeremophila‐1,9‐diene‐3,8‐dione ( 2 ), and a new friedelane‐type triterpenoid, friedelane‐3α,16β‐diol ( 4 ), along with six known terpenoids, 3 and 5 – 9 , have been isolated from the stems of Drypetes congestiflora. Their structures and relative configurations were elucidated on the basis of detailed spectroscopic analyses and by comparison of their NMR data with those reported in the literature. All of the compounds, 1 – 9 , were isolated for the first time from this species. Compound 3 exhibited moderate cytotoxic activities against the A549 and B16F10 cell lines. 相似文献
UVR8 is the only known plant photoreceptor that mediates light responses to UV‐B (280–315 nm) of the solar spectrum. UVR8 perceives a UV‐B signal via light‐induced dimer dissociation, which triggers a wide range of cellular responses involved in photomorphogenesis and photoprotection. Two recent crystal structures of Arabidopsis thaliana UVR8 (AtUVR8) have revealed unusual clustering of UV‐B‐absorbing Trp pigments at the dimer interface and provided a structural framework for further mechanistic investigation. This review summarizes recent advances in spectroscopic, computational and crystallographic studies on UVR8 that are directed toward full understanding of UV‐B perception at the molecular level. 相似文献