HPLC Determination of Chlorpropamide in Human Serum by Fluorogenic Derivatization Based on the Suzuki Coupling Reaction with Phenylboronic Acid

A fluorogenic derivatization method for the determination of chlorpropamide in human serum was developed by means of high-performance liquid chromatography (HPLC) with fluorescence detection. The Suzuki coupling reaction with a non-fluorescent reagent, phenylboronic acid (PBA), was employed to convert chlorpropamide into highly fluorescent biphenyl derivative. Chlorpropamide was extracted from human serum by liquid–liquid extraction with toluene after addition of hydrochloric acid, and subsequently reacted with PBA. Because the fluorogenic derivatization was highly selective for aryl halide, the proposed method allowed sensitive and selective detection of chlorpropamide with a detection limit (at a signal to noise ratio of 3) of 0.5 ng mL⁻¹. The sensitivity of our method was from 4 to 100 times better than HPLC–UV, gas chromatography, and LC-mass spectrometry.

     

HPLC Determination of Chlorpropamide in Human Serum by Fluorogenic Derivatization Based on the Suzuki Coupling Reaction with Phenylboronic Acid

A fluorogenic derivatization method for the determination of chlorpropamide in human serum was developed by means of high-performance liquid chromatography (HPLC) with fluorescence detection. The Suzuki coupling reaction with a non-fluorescent reagent, phenylboronic acid (PBA), was employed to convert chlorpropamide into highly fluorescent biphenyl derivative. Chlorpropamide was extracted from human serum by liquid–liquid extraction with toluene after addition of hydrochloric acid, and subsequently reacted with PBA. Because the fluorogenic derivatization was highly selective for aryl halide, the proposed method allowed sensitive and selective detection of chlorpropamide with a detection limit (at a signal to noise ratio of 3) of 0.5 ng mL^?1. The sensitivity of our method was from 4 to 100 times better than HPLC–UV, gas chromatography, and LC-mass spectrometry.     

Retrospective analyses of atmospheric polycyclic and nitropolycyclic aromatic hydrocarbons in an industrial area of a western site of Japan.

Thirteen polycyclic aromatic hydrocarbons (PAHs) and four nitropolycyclic aromatic hydrocarbons (NPAHs) on the surfaces of airborne particulates, which were collected at an industrial area of a western site of Japan during periods from 1976 to 1998, were retrospectively analyzed. PAHs and NPAHs were extracted from airborne particulates using hexane with ultrasonication, and then analyzed by HPLC systems with fluorescence detection and chemiluminescence detection, respectively. The total concentrations (mean +/- SD, n = 34) were 15.54 +/- 21.24 ng/m3 for PAHs and 5.85 +/- 8.16 pg/m3 for NPAHs. The concentrations of PAHs and NPAHs were found to be highest during the period between 1979 and 1982, and then reduced. The annual concentrations of PAHs and NPAHs were highly correlated with those of air pollutants from motor vehicle origin, such as carbon monoxide, suspended particulates and non-methane hydrocarbons. The results suggested that motor vehicle emissions were one of the predominant sources of atmospheric PAHs and NPAHs.     

Dual-mode of assembly of anthracene-based imidazolium salts both in non-polar organic solvents and in aqueous solution

Amphiphilic anthracene derivatives showed solvent-polarity-dependent fluorescence. Monomer emission and aggregation-induced emission (AIE) were observed in polar and non-polar organic solvents, respectively. AIE became predominant in aqueous solution in the case of hexafluorophosphate as a counter anion.     

Selective determination of ubiquinone in human plasma by HPLC with chemiluminescence reaction based on the redox cycle of quinone

Ubiquinone is an important biologically active compound in the living body. The determination of ubiquinone in human plasma is useful for the investigation of bioavailability of ubiquinone and for early diagnosis of several diseases. Therefore, we developed a high-performance liquid chromatography (HPLC) with chemiluminescence detection method for the analysis of ubiquinone in plasma samples. The method is based on luminol chemiluminescence detection of super oxide anion that is generated by the redox cycle reaction between ubiquinone and dithiothreitol. The HPLC system involved an octyl column with a mobile phase of methanol. Ubiquinone eluted from the column was mixed with dithiothreitol and luminol solutions simultaneously, and generated chemiluminescence was monitored by chemiluminescence detector. The calibration curve for standard ubiquinone solution was linear from 0.09 to 43.2 μg/mL (0.45–216 ng on column) with the correlation coefficient of 0.999, and the detection limit (S/N = 3) was 26 ng/mL (130 pg on column). Using the proposed HPLC method, the peak of ubiquinone in human plasma could be clearly detected on the chromatogram without any interference from plasma components.     

Fluorogenic derivatization of aryl halides based on the formation of biphenyl by Suzuki coupling reaction with phenylboronic acid

The fluorogenic derivatization method for aryl halide was developed for the first time. This method was based on the formation of fluorescent biphenyl structure by Suzuki coupling reaction between aryl halides and non-fluorescent phenylboronic acid (PBA). We measured the fluorescence spectra of the products obtained by the reaction of p-substituted aryl bromides (i.e., 4-bromobenzonitrile, 4-bromoanisole, 4-bromobenzoic acid ethyl ester and 4-bromotoluene) with PBA in the presence of palladium (II) acetate as a catalyst. The significant fluorescence at excitation maximum wavelength of 275–290 nm and emission maximum wavelength of 315–350 nm was detected in all the tested aryl bromides. This result demonstrated that non-fluorescent aryl bromides could be converted to the fluorescent biphenyl derivatives by the coupling reaction with non-fluorescent PBA. We tried to determine these aryl bromides by HPLC-fluorescence detection with pre-column derivatization. The aryl bromide derivatives were detected on the chromatogram within 30 min without any interfering peak derived from the reagent blank. The detection limits (S/N = 3) for aryl bromides were 13–157 fmol/injection.     

Hydrogen-bonded ionic liquid crystals: pyridinylmethylimidazolium as a versatile building block

Utilizing hydrogen bonding between pyridine and benzoic acids, hydrogen-bonded ionic liquid crystals were prepared from pyridinylmethylimidazolium and alkoxy-substituted benzoic acids. Depending on the number of alkoxy substituents, smectic C (SmC), rectangular columnar (Col_r), and cubic (Cub) phases were obtained from mono-, di-, and tri-substituted benzoic acids, respectively. These phases were investigated with X-ray diffraction, differential scanning calorimeter, and polarized optical microscopy.     

Determination of artemisinin in human serum by high-performance liquid chromatography with on-line UV irradiation and peroxyoxalate chemiluminescence detection

Artemisinin is an antimalarial drug containing an internal endoperoxide linkage in its structure. A simple, selective and sensitive high-performance liquid chromatography (HPLC)-peroxyoxalate chemiluminescence (PO-CL) method for the determination of artemisinin was developed. This method is based on the fact that endoperoxide in artemisinin structure can be converted to hydrogen peroxide (H(2)O(2)) under ultraviolet (UV) irradiation and the generated hydrogen peroxide can be measured using PO-CL detection. The HPLC-PO-CL system was optimized on a mobile phase, post column chemiluminescence reagent, UV source and irradiation time. In addition, the system was combined with simple liquid-liquid extraction using n-hexane that allowed selective and sensitive determination of artemisinin in serum. The limit of detection using 0.5 mL of blood was 0.062 micromol/L (17.5 ng/mL) at a signal-to-noise ratio of 3. Calibration curve obtained for artemisinin in human serum 4-80 micromol/L (1.1-22.6 microg/mL) showed a good linearity (r = 0.999).     

Discovery of new orally active phosphodiesterase (PDE4) inhibitors

A series of 4-anilinopyrazolopyridine derivatives were synthesized and biologically evaluated as inhibitors of phosphodiesterase (PDE4). Chemical modification of 3, a structurally new chemical lead that was found in our in-house library, was focused on 1- and 3-substituents. Full details of the discovery of a new orally active chemical lead 5 are presented. Structure-activity relationship data, pharmacological evaluation, and the subtype selectivity study are also presented.     

Why chiral tartaric imide derivatives give large helical twisting powers in nematic liquid crystal phases: substituent-effect approach to investigate intermolecular interactions between dopant and liquid crystalline molecules

Novel C₂-symmetric chiral dopant derivatives, namely, N-substituted (2R, 3R)-2,3-bis(4-(4-octyloxyphenyl)benzoyloxy)succinimides1a-h, were synthesised, and the effects of the N-substituent and imide-carbonyl groups on the helical twisting powers (HTPs) were investigated in two nematic liquid crystalline compounds, 4-n-pentyl-4?-cyanobiphenyl (5CB) and N-(4-ethoxybenzylidene)-4-n-butylaniline (EBBA). As a result, it was clarified that the bulkiness of the N-substituents has a significant correlation with the HTPs, and the imide-carbonyl group interacts strongly with the cyano group of 5CB to give high HTPs in the nematic phases. However, it is assumed that the imide-carbonyl groups of the dopants do not have strong electrostatic attractive interactions with EBBA molecules in the nematic phase to afford the moderate HTPs.