Differentiation of volatile aromatic isomers and structural elucidation of volatile compounds in essential oils by combination of HPLC separation and crystalline sponge method.

Structure elucidation of volatile aromatic isomers at trace level has long been considered as an elusive task, due to their structural similarities and similar polarities, even with the aid of many spectroscopic techniques such as mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. Single-crystal X-ray diffraction (SCD) is recognized as one of the most powerful structural elucidation techniques. The recently developed crystalline sponge method overcomes the intrinsic limitation of SCD that the target molecules must be single crystals, being able to analyze non-crystalline and trace-amount compounds without any special treatment. In order to investigate whether the crystalline sponge method could be used for the structure elucidation of closely related isomers or other volatile and even oily compounds in complex mixtures at trace level, we combined HPLC separation with the crystalline sponge method for X-ray crystallographic analysis. In this paper, two pairs of volatile aromatic isomers including cis/trans isomers of asarone and positional isomers of carvacrol and thymol, as well as the main volatile component in essential oil extracted from Acorus Tatarinowii, were first isolated by HPLC and encapsulated into the crystalline sponge then elucidated by X-ray crystallographic analysis. Direct observation of these volatile compounds by X-ray crystallography was achieved using only microgram quantities without crystallization or derivatization. Unambiguous identification of these compounds was realized without reference standards. This strategy offers a promising platform capable of providing high-confidence detailed structural information of closely related isomers as well as other volatile and even oily compounds in complex mixtures in microgram quantities.

Rapid, sensitive and selective HPLC-MS/MS method for the quantification of topically applied besifloxacin in rabbit plasma and ocular tissues: Application to a pharmacokinetic study.

Besifloxacin is a fourth-generation broad-spectrum fluoroquinolone registered for the topical treatment of bacterial conjunctivitis. In this study, a rapid, sensitive and selective liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for quantification of besifloxacin in rabbit plasma and ocular tissues using nateglinide as the internal standard (IS). The analyte and IS were separated on a Sepax GP-Phenyl column by isocratic elution with methanol-acetonitrile-5 mM ammonium formate-formic acid (29:55:16:0.1, v/v/v/v) as the mobile phase at a flow rate of 1.2 mL/min, and the total run time was 3.0 min. An electrospray ionization (ESI) source was applied and operated in the positive ion mode; multiple reaction monitoring (MRM) mode was used for quantification, and the monitored transitions were 394.2→377.1 for besifloxacin and m/z 318.3→166.1 for the IS. The calibration curve was linear over the range of 0.103-206 ng/mL for plasma and 2.06-2060 ng/mL for tears, aqueous humor, conjunctiva and cornea with correlation coefficient (r) greater than 0.99. The lower limit of quantification (LLOQ) for besifloxacin was 0.103 ng/mL for plasma and 2.06 ng/mL for other ocular tissues with good accuracy and precision. Intra- and inter-batch precision were both lower than 15% and accuracy ranged from 85% to 115% at all QC levels. The method was successfully applied to the pharmacokinetic study of besifloxacin in rabbit plasma and ocular tissues after single and multiple topical administrations.

[Study on UPLC Fingerprint of Corydalis bungeana].

OBJECTIVE: To establish an Ultra Performance Liquid Chromatography fingerprint of Corydalis bungeana from different habitats. METHODS: UPLC-PDA was adopted to analysis ten batches of Corydalis bungeana from different habitats with Phenomenex Luna C18 column (250 mm x 4.6 mm, 5 µm) eluted with the mobile phase of acetonitrile and 0. 02% triethylamine in a gradient mode. The flow rate was 0.3 mL/min and the column temperature was 30 °C. The detection wavelength was set at 289 nm. RESULTS: The fingerprints of ten batches of Corydalis bungeana from different habitats had 13 common peaks, three of them were identified. The similarities were larger than 0.80. Ten batches of samples were divided into three categories by cluster analysis. Three principal components were ob- served via principal component analysis and the value of three principal components accounted for 89. 607% of the total variance. Two major chemical components of Corydalis bungeana were confirmed. CONCLUSION: The high-performance and rapid method is successfully used for fingerprint analysis and can be used to evaluate the quality of Corydalis bungeana.

Development and validation of a high-performance liquid chromatography-tandem mass spectrometry method for the rapid simultaneous quantification of aconitine, mesaconitine, and hypaconitine in rat plasma after oral administration of Sini decoction.

A rapid, sensitive, and specific liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS) method was developed and validated for simultaneous determination of aconitine (AC), mesaconitine (MA), and hypaconitine (HA), the three toxic constituents from Sini decoction (SND) in rat plasma. After the addition of citalopram as the internal standard (IS), plasma samples were basified with 100 microL 10% ammonium hydroxide, and then extracted with 1 mL ethyl acetate. Chromatographic separation was performed on a CN column (250 mm x 4.6 mm, 5 microm) with a mobile phase of methanol/40 mM ammonium acetate/formic acid (950:45:5, v/v/v) at the flow rate of 1.0 mL/min. Analytes were determined in a triple-quadrupole mass spectrometer in the selected reaction-monitoring (SRM) mode using electrospray source with positive mode. The method was validated over the concentration ranges of 0.01-10 ng/mL for AC, MA, and HA. The variation coefficients were always < 15% for both intraday and interday precision for each analyte. Mean accuracies were also within +/-15%. The method was proved to be sensitive, rapid, specific, accurate, and reproducible. It has been successfully applied to the pharmacokinetics study on rats after oral administration of SND.

Pharmacokinetic properties of S-adenosylmethionine after oral and intravenous administration of its tosylate disulfate salt: a multiple-dose, open-label, parallel-group study in healthy Chinese volunteers.

BACKGROUND: S-adenosylmethionine (SAMe) is an endogenous molecule that plays an important role in cellular metabolism. Despite being widely used as a dietary supplement with claimed benefits for numerous conditions, there is little information about the pharmacokinetic properties of exogenous SAMe. OBJECTIVES: One aim of this study was to characterize the pharmacokinetic properties of SAMe after administration of single and multiple doses of orally and intravenously administered SAMe tosylate disulfate (STD) in healthy male and female Chinese volunteers. Because men have higher erythrocyte levels of endogenous SAMe than do women, we also assessed the effects of sex on the disposition of SAMe. METHODS: A simple and sensitive assay for SAMe based on liquid chromatography-mass spectrometry using selected-ion monitoring of analyte and acyclovir as internal standard was developed and validated. The assay was used to study the pharmacokinetic properties of SAMe. STD was administered as single and multiple doses of enteric-coated tablets and IV infusion of STD to groups of healthy native Chinese volunteers. After an overnight fast, male and female Chinese volunteers were assigned to receive STD 1000 mg for 5 days, either in enteric-coated tablet formulation or as a 250-mL IV infusion. Blood samples were collected 24 hours after the first and last dose and used for determining plasma SAMe concentrations and pharmacokinetic parameters. For the oral formulation, SAMe concentrations were corrected for concentrations of endogenous SAMe. Pharmacokinetic parameters were calculated for men and women separately and for the total group of volunteers. Adverse events were monitored using a physician during blood collection and by spontaneous reporting. RESULTS: Twenty healthy volunteers were enrolled (oral formulation: 5 men, 5 women; mean [SD] age, 24.1 [4.7] years [range, 21-37 years]; mean [SD] weight, 59.9 [4.8] kg [range, 54-70 kg]; IV formulation: 5 men, 5 women; mean [SD] age, 22.6 [1.8] years [range, 21-27 years]; mean [SD] weight, 59.5 [5.4] kg [range, 53-67 kg]). None of the between-sex differences in SAMe pharmacokinetic properties were significant. The (mean [SD]) pharmacokinetic properties of singledose oral SAMe in men and women, respectively, were as follows: C(max), 2.37 (1.58) and 2.50 (1.83) micromol/L; T(max), 5.40 (1.14) and 5.20 (1.48) hours; AUC(0-24), 8.56 (5.16) and 10.3 (8.0) micromol/L/h; and t(1/2beta), 6.06 (1.80) and 6.28 (2.60) hours. Corresponding values with the single-dose IV formulation were: C(max), 127 (49) and 211 (94) micromol/L; T(max), 1.90 (0.22) and 1.60 (0.22) hours; AUC(0-24), 329 (84) and 480 (176) micromol/L/h; and t(1/2beta), 4.34 (0.57) and 3.83 (0.78) hours. The single-dose oral:IV ratios of AUC(0-24) in men and women, respectively, were 2.60% and 2.14% (degrees of fluctuation: 4.96 [1.77] and 9.49 [0.91]). The pharmacokinetic properties of multiple-dose oral and IV SAMe were not significantly different from those with single-dose administration. None of the volunteers reported any adverse events during the study. CONCLUSIONS: In this small study in healthy Chinese volunteers, there were no significant differences in the pharmacokinetic parameters of SAMe between men and women or between single- and multiple-dose administration of STD 1000 mg administered orally or intravenously. No evidence of accumulation of SAMe in plasma was found on multiple dosing. Both enteric-coated tablets and the IV infusion were well tolerated in these volunteers.

[Enantioseparation of amlodipine maleate by capillary electrophoresis using colominic acid as a chiral selector and the mechanism of chiral recognition].

AIM: Colominic acid, a novel chiral selector, was applied to enantioseparation of dihydropyridine derivative by capillary electrophoresis. A new method was developed for enantioseparation of amlodipine maleate, a novel calcium channel blocking therapeutic agent. The chiral recognition mechanism of colominic acid to amlodipine maleate was studied. METHODS: Capillary electrophoresis was performed, and the effects of separation conditions on chiral separation were examined, including concentration of chiral selector, buffer pH, capillary temperature, applied voltage and molecular mass of colominic acid. RESULTS: The optimum conditions were additive concentration of 8.0%, buffer pH at 3.00, capillary temperature at 15 degrees C, 12 kV for applied voltage and 3 x 10(4) for molecular mass of colominic acid. Under optimum conditions complete separation was achieved between the enantiomers of amlodipine maleate with resolution as high as 2.20. CONCLUSION: The cliral separation was based on the multipoint recognition between colominic acid and amlodipine maleate. It is recommended that this simple, rapid and selective method be used for enantioseparation of amlodipine maleate. As far as polysaccharides were concerned, colominic acid was first used for enantioseparation of amlodipine maleate.