Hideki Hakamata

Simultaneous determination of β-sitosterol, campesterol, stigmasterol, and brassicasterol in serum by high-performance liquid chromatography with electrochemical detection

A simple method for the determination of phytosterols such as β-sitosterol, campesterol, stigmasterol, and brassicasterol has been developed using high-performance liquid chromatography with electrochemical detection (HPLC-ECD). Under optimized conditions, the current peak height was linearly related to the amount of phytosterol injected, ranging from 10 to 200 μmol L−1 (r = 0.999). The relative standard deviation (RSD) was less than 3.1% (100 μmol L−1, n = 6). The detection limit (S/N = 3) of phytosterol was less than 3.4 μmol L−1 (17 pmol). Phytosterols spiked into the control human and rat sera were determined by the present method with recovery rates of more than 80% and RSDs (n = 3) of less than 4.2%. This method has been successfully applied to the monitoring of experimental phytosterolemia in rats induced by a high-phytosterol diet. Taken together, we found this method, which does not require a derivatization step, is both simple and useful for the simultaneous determination of serum phytosterols, providing an alternative tool for the diagnosis of phytosterolemia.

Column switching high-performance liquid chromatography with two channels electrochemical detection for high-sensitive determination of isoflavones.

Column switching HPLC with electrochemical detection (HPLC-ED), which consists of one pre-column and two electrochemical detectors subsequent to each analytical column, called HPLC-2ED, has been developed for determining isoflavones (daidzin, genistin, daidzein, and genistein) with high sensitivity. In the present HPLC-2ED, the eluted daidzin and genistin from the pre-column were separated on an analytical column using a methanol-water-phosphoric acid mixture (30:70:0.5) as the mobile phase (MP), and daidzein and genistein were separated on another analytical column using a methanol-water-phosphoric acid mixture (50:50:0.5). The way of the elute flow from the pre-column was changed by rotating the switching valve at 17 min. The difference in retention times of genistein between isocratic HPLC-ED and HPLC-2ED was 52.2 min. The detection limit (S/N=3) per column injection (5 microL) of genistein was 0.5 pg. The sensitivity by the present method is superior to that of previously reported gradient HPLC-ED for the determination of isoflavones.

Simultaneous determination of serum lathosterol and cholesterol by semi-micro high-performance liquid chromatography with electrochemical detection.

A simple method has been developed for the simultaneous determination of lathosterol and cholesterol by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). Lathosterol was found to be electrochemically oxidized and its current peak height was linearly related to the amount of lathosterol injected, ranging from 0.15 μmol/L to 300 μmol/L (r=0.995). Similar results were obtained with cholesterol from 15 μmol/L to 600 μmol/L (r=0.995). The separation was carried out with an ODS column, acetonitrile containing 30 mmol/L lithium perchlorate as a mobile phase, and an applied potential at +2.8 V vs. Ag/AgCl. The detection limit (S/N=3) of lathosterol as well as cholesterol was 0.03 μmol/L (0.15 pmol). Total lathosterol in control human and rat serum was determined by the present method with a recovery of more than 95.8% and an RSD (n=5) of less than 7.3%. The present method was applied to an experiment with rats to examine the effect of lathosterol feeding. There were no significant changes in serum lathosterol or cholesterol levels in rats fed with a high-lathosterol diet for six days. Therefore, we found this method to be both simple and useful for the simultaneous determination of lathosterol and cholesterol in serum.

Determination of oxysterols in oxidatively modified low-density lipoprotein by semi-micro high-performance liquid chromatography with electrochemical detection.

A simple method for the determination of oxysterols was developed by semi-micro high-performance liquid chromatography with electrochemical detection (semi-micro HPLC-ECD). Semi-micro HPLC-ECD was established using a C30 microbore column, acetonitrile containing 50 mmol/L LiClO(4) as a mobile phase, and an applied potential at +2.8V versus Ag/AgCl. The current peak height was linearly related to the amount of sterol injected from 12.5 to 250 pmol (r>0.999) with a relative standard deviation (RSD) of less than 2.9% (n=6). This method was applied to the determination of seven oxysterols in oxidatively modified low-density lipoprotein (Ox-LDL). Oxysterols were determined with a recovery of more than 78.0% and an RSD of less than 2.9% (n=6) except for 7-ketocholesterol. 7-Ketocholesterol was determined as a sum of intact 7-ketocholesterol and its degradation product on saponification, cholesta-3,5-dien-7-one, with a recovery of 98.0% and an RSD of 2.5% (n=6). From these results, the current method enabled the simultaneous determination of seven oxysterols without any derivatization, providing a useful tool for the assessment of oxysterol contents in Ox-LDL.

Three-channel column-switching high-performance liquid chromatography with electrochemical detection for determining bioactive redox components in Salvia miltiorrhiza.

Three-channel column-switching high-performance liquid chromatography with electrochemical detection (3LC-3ED), which consists of three flow ways, two switching valves, four columns, and three electrochemical detectors, was developed for determining various redox components in Salvia miltiorrhiza with high sensitivity. In this study, the analytes were divided into three groups as follow: Group I [salvianic acid A (Danshensu) sodium salt (DSS), protocatechuic acid (PA), protocatechuic aldehyde (PAD), and caffeic acid (CA)], Group II [rosmarinic acid (RA), lithospermic acid (LA), and salvianolic acid B (SAB)], and Group III [cryptotanshinone (Cry), tanshinone I (Tan I), and tanshinone IIA (Tan IIA)]. By rotating each switching valve to change the elute flow way, the components in Groups I, II, and III were directed into the oxidative (+0.7 V), another oxidative (+0.7 V), and reductive (-0.2V) detection channels, respectively. Chromatographic peaks of components in Groups I, II, and III appeared within 69, 53, and 60 min, respectively, in each channel. The detection limits of DSS, PA, PAD, CA, RA, LA, SAB, Cry, Tan I, and Tan IIA were 4.2, 2.8, 10, 10, 3.9, 3.8, 3.0, 132, 119, and 109 fmol, respectively, thus the sensitivity by the present 3LC-3ED is superior to those of previously reported gradient LC-ED and LC with UV detection. As an application, the phenolic acid contents and tanshinones in nine batches of S. miltiorrhiza were successfully determined.

An ultra performance liquid chromatographic method for determining phytosterol uptake by Caco-2 cells

A simple method for the determination of cellular uptake of phytosterols by Caco-2 cells has been developed by ultra performance liquid chromatography with ultraviolet detection (UPLC-UV). UPLC-UV was established using an ODS column, acetonitrile/H(2)O (9:1, v/v) as a mobile phase, and a detection wavelength at 210 nm. As analytes, β-sitosterol, campesterol, stigmasterol, and brassicasterol were selected based on the abundance in foods and the similarity of their structures. A linear relation was observed between the peak area and the amount of sterol injected from 50 to 2000 pmol (r>0.999) with a relative standard deviation (RSD) of less than 2.5% (n=6). This method was applied to the determination of cellular uptake of phytosterols by Caco-2 cells. Recovery tests showed that phytosterols were extracted from the cell lysates by chloroform and determined by UPLC-UV with a recovery rate of more than 80.2% and an RSD of less than 11.3% (n=3). When Caco-2 cells were incubated with phytosterols at 37°C, their uptake was increased with time in a concentration-dependent manner. This method will be useful for the simultaneous determination of cellular phytosterols in an in vitro intestine model.

Simultaneous determination of azaperone and azaperol in animal tissues by HPLC with confirmation by electrospray ionization mass spectrometry

A simple method is described for the determination of azaperone and its metabolite, azaperol, in animal tissues by high-performance liquid chromatography with ultraviolet detection (HPLC/UV). Chromatography was performed using an ODS column, an acetonitrile-0.025% aqueous diethylamine mixture (2:3, v/v) as a mobile phase and UV detection at 250 nm. Peak heights were found linearly related to the concentrations injected from 0.05 to 2 microg/mL (r>0.999). Azaperone and azaperol spiked into several animal tissues were solubilized in 1 mol/L NaOH, extracted with hexane, transferred to 0.1 mol/L H(2)SO(4) and re-extracted with hexane in a mild basic condition. Recoveries of both compounds from 12 types of samples (swine muscle, swine adipose tissue, swine liver, bovine muscle, bovine adipose tissue, bovine liver, poultry muscle, poultry adipose tissue, poultry liver, bovine milk, poultry egg, and salmon muscle) were more than 72%. The lower limit of quantification of was 0.025 microg/g. Azaperone and azaperol at 0.1 microg/g were confirmed by LC/MS. In conclusion, we found this method is both simple and useful for the determination of azaperone and azaperol in a variety of animal tissues for food safety and veterinary applications.

Simultaneous determination of various bioactive redox components in Shuang-Huang-Lian preparations using a novel three-channel isocratic elution liquid chromatography with electrochemical detection system.

A novel three-channel isocratic elution high performance liquid chromatography with electrochemical detection (3LC-ECD) system was developed for the simultaneous determination of various bioactive redox components in Shuang-Huang-Lian (SHL) preparations. This 3LC-ECD system consists of three isocratic elution flow ways, two switching valves, four columns, and three electrochemical detectors. Through alternately rotating switching valves to change the elution flow way, six caffeoylquinic acids, four flavonoids, and one phenylethanoid glycoside compound were simultaneously determined within 70 min by the present 3LC-ECD method, in which three compounds of protocatechuic aldehyde, propyl gallate, and kaempferol were used as internal standards. The results demonstrated that the present 3LC-ECD method has achieved desired linearity (r>0.999), precision (relative standard deviation <2.5%), accuracy (recovery, 95.6-103.6%), and high sensitivity (limit of detection, 0.11-0.90 ng/mL). In addition, we successfully determined the contents of these 11 bioactive redox components in 14 batches of SHL oral liquid and 12 batches of SHL lyophilized powder for injection produced by different manufacturers in China.

Determination of serum cholestanol by semi‐micro high‐performance liquid chromatography with electrochemical detection

A simple and sensitive method that dose not require derivatization for determining cholestanol has been developed using HPLC with electrochemical detection (HPLC-ECD). The current peak height was linearly related to the amount of cholestanol injected, ranging from 1 to 200 muM (r = 0.999). The detection limit (S/N = 3) of cholestanol was 0.23 muM (1.2 pmol). Total cholestanol in control human and mouse serum was determined by the present method with a recovery rate of more than 90% and an RSD (n = 5) of less than 7.3%. Further, this method was successfully applied to monitor experimental hypercholestanolemia in mice fed a high-cholestanol diet, an animal model of cerebrotendinous xanthomatosis (CTX). In conclusion, we found this method to be both simple and useful for the determination of cholestanol in serum, helping in the diagnosis of CTX.

2-(Pyridinium-1-yl)-1,1-bis(perfluoroalkylsulfonyl)ethan-1-ide: A Practical Reagent for Synthesis of Strongly Acidic 1,1-Bis(perfluoroalkylsulfonyl)alkanes

On mixing (Rf SO2 )2 CH2 (Rf =perfluoroalkyl), paraformaldehyde, and substituted pyridines, a three-component reaction proceeded smoothly to give unusual zwitterions bearing both pyridinium and stabilized carbanion moieties in good to excellent yields. Of these, 2-fluoropyridinium derivatives rapidly dissociated in acetonitrile to give equilibrium mixtures of the zwitterions and (Rf SO2 )2 C=CH2 /2-fluoropyridine, as confirmed by detailed variable-temperature NMR studies. The dynamic behavior of such 2-fluoropyridinium compounds allows them to be used as shelf-stable, easy-to-handle sources of (Rf SO2 )2 C=CH2 . With these reagents, strongly acidic carbon acids (Rf SO2 )2 CHR were synthesized, which served as a new type of acid catalysts. Moreover, C-C bond-forming reactions with a ketene silyl acetal proceeded efficiently with Tf2 C=CH2 generated in situ.