A simplified D3 -creatine dilution method for skeletal muscle mass determination with dynamic correction of creatinine and D3 -creatinine using ultra-performance liquid chromatography-tandem mass spectrometry

This study developed a simple method for muscle mass determination based on D3 -creatine dilution by removing the matrix effects of ultra-performance liquid chromatography-tandem mass spectrometry analysis through mutual correction of creatinine and D3 -creatinine. Rats were administered an oral tracer dose of D3 -creatine at age 6 weeks. Creatinine and D3 -creatinine in urine were detected using ultra-performance liquid chromatography-tandem mass spectrometry after diluting 20 times to obtain D3 -creatinine enrichment factor (mole percent excess). The mole percent excess obtained from peak area could be used to calculate muscle mass using the improved formula. The limit of detection was 0.500 ng/mL for D3 -creatinine. Creatinine and D3 -creatinine could be mutually corrected because of the same matrix effect, and D3 -creatine spillage was negligible within 0.22%. Isotopic steady time was consistent with that obtained using conventional methods. Bland-Altman plots demonstrated the satisfying consistency between the proposed method and magnetic resonance imaging. This is a simple and rapid measuring method of muscle mass based on D3 -creatine dilution that requires no accurate quantification of creatinine and D3 -creatinine concentrations and no urine sample collection to obtain D3 -creatine spillage.

Pharmacokinetics, Bioequivalence, and Safety of Esomeprazole Magnesium Enteric-Coated Capsules in Healthy Chinese Subjects

This bioequivalence study is critically important for drug production. Recently, a local pharmaceutical company produced esomeprazole magnesium enteric-coated capsules, a major drug to help to eradicate Helicobacter pylori, but the bioequivalence is not well known. The present study aimed to evaluate the bioequivalence of the 2 esomeprazole magnesium enteric-coated capsules and their pharmacokinetics and safety in 3 biological equivalence trials: fasting, feeding, and mixing. The fasting and mixing trials used single-centered randomized, open-label, single-dose, 2-treatment, 2-period, and 2-sequence crossover design, while the fed trials used single-centered, randomized, open-label, single-dose, 2-treatment, 3-period, 3-sequence partial crossover design. For the fasting and mixing trials, each of the 32 subjects was fasted overnight prior to taking the test preparations or reference preparations. In the fed trial, 54 subjects were given a high-fat meal 1 hour before the drugs were administered. Blood specimens from all subjects were collected against the light within 14 hours, with the plasma drug concentration being detected by the validated ultra-performance liquid chromatography-tandem mass spectrometry analysis method. Geometric mean ratio of maximum concentration, the area under the concentration-time curve from time zero to the last measurable concentration, and area under the concentration-time curve from time zero to infinity with 90% confidence interval were calculated. The data from fasting, mixing, and fed trials met the bioequivalence criteria. No serious adverse reactions were found, suggesting that the test and reference preparations of esomeprazole magnesium enteric capsules have similar safety profile.

Pharmacokinetics and tissue distribution of five bioactive components in the Corydalis yanhusuo total alkaloids transdermal patch following Shenque acupoint application in rats assessed by ultra-performance liquid chromatography-tandem mass spectrometry

The purpose of this study was to evaluate the pharmacokinetics and tissue distribution of the Corydalis yanhusuo total alkaloids transdermal patch (CTTP) following Shenque acupoint application in rats. The concentrations of corydaline, tetrahydropalmatine, tetrahydrocolumbamine, protopine, and dehydrocorydaline in rat plasma and various tissues were simultaneously detected by ultra-performance liquid chromatography-tandem mass spectrometry after Shenque acupoint administration of CTTP. Plasma, heart, liver, spleen, lung, and kidney tissue samples were collected at specific times and separated by gradient elution on an ACQUITY UPLC HSS T3 column (1.8 μm, 100 mm × 2.1 mm) with a mobile phase of 0.01% formic acid aqueous solution and acetonitrile-0.01% formic acid. The methodological results showed that the selectivity, linear range, accuracy, precision, stability, matrix effect, and extraction recovery of the established method met the requirements of biological sample analysis. The results indicated that CTTP following Shenque acupoint administration rapidly delivered adequate drug into rat blood and maintained an effective plasma level for a significantly longer time than non-acupoint administration. Furthermore, CTTP effectively reached the liver through Shenque acupoint administration and showed tissue selectivity. The data obtained could provide a prospect for the treatment of chronic pain with CTTP following Shenque acupoint application.

Cellular toxicity and pharmacokinetic study of butachlor by ultra-performance liquid chromatography-tandem mass spectrometry based on tandem mass spectrometry cubed technique

Butachlor is an aromatic amide compound that plays a role as a herbicide, a xenobiotic, and an environmental contaminant. The aim of this work was to develop a highly selective and sensitive ultra-performance liquid chromatography-tandem mass spectrometry method based on the tandem mass spectrometry cubed technique to determine butachlor in a biological matrix. Butachlor and internal standard acetochlor were separated on a Waters Acquity ultra-performance liquid chromatography BEH C₁₈ column (2.1 × 50 mm, 1.7 μm) with gradient elution using 0.1% formic acid aqueous solution (A) and acetonitrile (B) as mobile phases. The transitions selected for tandem mass spectrometry cubed quantitative analysis in positive ion mode were: for butachlor, mass-to-charge ratio 312.2→238.1→162.1; for acetochlor, mass-to-charge ratio 270.1→224.0→148.1. The total running time for each sample was 5.5 min. The ultra-performance liquid chromatography-tandem mass spectrometry cubed method showed a linear relationship (R² ≥ 0.995) in the concentration range of 0.5-100 ng/ml. The intra and interday accuracies are within the range of -10.6%-4.3% and precisions are between 4.48% and 13.14%. The novelty of the method is the use of tandem mass spectrometry cubed scanning mode, which improves selectivity and sensitivity. The results indicated that butachlor was cellular toxic. The safety of butachlor should be considered when it is used as a herbicide.

[Determination of four melamine and its derivatives in urine by ultra-performance liquid chromatography-tandem mass spectrometry]

OBJECTIVE

To establish a method for simultaneous detection of melamine(MEL), ammeline(AMN), ammelide(AMD) and cyanuric acid(CYA) in urine by ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).

METHODS

After the urine sample was added to the internal standard, they were mixed by acetonitrile, ultrasonic extraction and centrifugation, enriched by MCX or MAX solid phase extraction column, eluted with 5% ammoniated methanol or 2% formic acid methanol, dried under nitrogen at 40 ℃, separated by Amide chromatography column(2.1 mm×100 mm, 1.7 μm), qualitatively and quantitatively analyzed by mass spectrometer in the simultaneous scanning mode of positive and negative ions.

RESULTS

Melamine and its derivatives were completely separated with great chromatography peak. The limit of detection(LOD) for melamine, ammeline, ammelide and cyanuric acid were 0.03, 0.04, 0.04 and 0.05 ng/mL, and the limit of quantification(LOQ) were 0.11, 0.12, 0.14 and 0.15 ng/mL, respectively. The recovery rate of standard addition samples of 0.2, 5, 50 and 200 ng/mL ranged from 94.6% to 106.5%, the intra-day precision was between 0.73% and 8.34%, and the inter-day precision was less than 6.80%(n=6). At low concentrations, AMD and CYA mainly showed matrix enhancing effect, while AMN showed matrix inhibitory effect with increasing concentration. The overall detection rate of melamine and its derivatives was 75.0% in 60 parcels of random urine. The average concentration of urinary melamine and its derivatives were higher in men.

CONCLUSION

UPLC-MS/MS can simultaneously determine four melamine and its derivatives in urine. The LOD and LOQ of the current method were low with great accuracy and precision.

Quantitation of six steroid hormones by ultra-performance liquid chromatography-tandem mass spectrometry in plasma and prefrontal cortex samples from rats with chronic unpredictable mild stress-induced depression

Steroid hormones such as glucocorticoids and their metabolites are closely related to mental diseases and neuroendocrine diseases. Quantitative analysis of these substances will help in understanding their roles in related research fields. In this study, an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to detect the concentration of corticosterone (CORT) and its metabolites, progesterone (PROG) and testosterone in rat plasma and prefrontal cortex (PFC), and was applied to investigate the changes in hormones in rats with depression induced by chronic unpredictable mild stress (CUMS). The method was shown to be linear in the quantitation range for all analytes. Intra- and inter-day accuracy and precision were between 80% and 120%. Furthermore, we found that the level of CORT in plasma and PFC increased, whereas that of 11-dehydrocorticosterone (11-DHCORT) as well as the ratio of 11-DHCORT and CORT declined in rats with CUMS-induced depression. The trends of these changes in central PFC and peripheral plasma were consistent. In conclusion, this study successfully established an UPLC-MS/MS method for simultaneous measurement of CORT and its metabolites, PROG and testosterone in rat plasma and PFC, and applied it to rats with depression. The method could be further applied to the research of depression and diseases related to these steroid hormones.

Sensitive, wide-range and high-throughput quantification of cyclosporine in whole blood using ultra-performance liquid chromatography coupled to tandem mass spectrometry and comparison with an antibody-conjugated magnetic immunoassay

Because either trough or peak concentration at 2 h after administration is measured in routine therapeutic drug monitoring for cyclosporine A (CyA), a quantification method with a wide-range calibration curve capable of simultaneously measuring both concentrations is required. We developed a sensitive, wide-range and high-throughput quantification method for CyA in whole blood using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and compared patients' blood CyA levels measured by UPLC-MS/MS and antibody-conjugated magnetic immunoassay (ACMIA). Whole blood samples were prepared by solid-phase extraction using Oasis HLB μElution plate. The UPLC-MS/MS assay showed excellent linearity over a wide calibration range of 5-2500 ng/mL. Within-batch accuracy and precision as well as batch-to-batch accuracy and precision fulfilled the criteria of US Food and Drug Administration guidelines. The blood CyA concentrations measured by the UPLC-MS/MS assay correlated strongly with those measured by ACMIA. A Bland-Altman plot showed a fixed error between CyA concentrations measured by the two methods, and the concentrations measured by the UPLC-MS/MS method were consistently lower than those measured by ACMIA. We have succeeded to develop a sensitive, wide-range and high-throughput quantification method for CyA in whole blood using UPLC-MS/MS.

Orally Administered Koumine Persists Longer in the Plasma of Aged Rats Than That of Adult Rats as Assessed by Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry

Aging leads to changes in nearly all pharmacokinetic phases. Koumine (KM), an alkaloid derived from Gelsemium elegans Benth., is effective against age-associated chronic diseases, but its dose proportionality following oral administration in aged individuals remains unknown. Herein, we established and validated a simple method that requires low sample volumes to determine KM concentration in rats using ultra-performance liquid chromatography-tandem mass spectrometry. The maximum plasma concentration (C_max) of 7 mg·kg⁻¹ KM was ~12-fold and ~24-fold higher than that of 0.28 mg·kg⁻¹ KM in adult and aged rats, respectively (P < 0.01). Time to reach C_max (T_max) for 7 mg·kg⁻¹ KM was 4-fold longer in aged rats (P < 0.05). The area under the curve (AUC) of 7 mg·kg⁻¹ KM was >17-fold and >43-fold higher than those of 0.28 mg·kg⁻¹ KM in adult and aged rats, respectively (P < 0.01). The half-life (t_1/2) of 7 mg·kg⁻¹ KM was over 4-fold longer than that of 0.28 mg·kg⁻¹ KM in adult rats (P < 0.01). The t_1/2 of 1.4 and 7 mg·kg⁻¹ KM were 1.5~2-fold longer, than that of 0.28 mg·kg⁻¹ KM in aged rats (P < 0.05). The clearance rate of 7 mg·kg⁻¹ KM was significantly lower in aged than in adult rats (P < 0.05). For 7.0 mg·kg⁻¹ KM, the C_max in aged rats was higher than in adult rats during the T_max period (P < 0.05). In aged rats, the AUC for KM was >2.5-fold higher (P < 0.05) and the t_1/2 was >60% longer than in adult rats (P < 0.05). These results help interpret the pharmacokinetics of KM in aging-associated diseases.

An improved method for measurement of testosterone in human plasma and saliva by ultra-performance liquid chromatography-tandem mass spectrometry

The aim of the study was to develop and validate a practical assay of clinically relevant testosterone levels in human plasma and saliva. We performed ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis on Atlantis dC18 steel column using a mobile phase of 2-mM ammonium acetate and acetonitrile (20:80, v: v) that was delivered at 0.3 ml/min. After adding d3-testosterone as an internal standard (IS), we extracted plasma and salivary samples with methyl tert-butyl ether. Mass spectrometry was performed in electrospray positive-ion mode. Targeted ion transitions were examined at m/z 289.18 → 97.04 and 292.24 → 97.04 for testosterone and IS, respectively. We validated the method according to the US Food and Drug Administration guidelines. Elution times for testosterone and IS were both around 1.35 min. Testosterone level was linearly associated (r ² = 0.9975 and 0.9958) with peak area ratio of testosterone to IS between 0.5-50 ng/ml and 10-400 pg/ml in plasma and saliva, respectively. The coefficient of variation and bias were ≤12.6% and ≤±12.1% in plasma and ≤10.2% and ≤±5.3% in saliva. The extraction recovery of testosterone was ≥92% from plasma and ≥94% from saliva. Testosterone was stable (≥91%) for 24 h at room temperature and for 8 weeks at -20°C in both plasma and salivary samples. We report a simple, validated, UPLC-MS/MS assay that can be used to determine clinically relevant levels of testosterone in human plasma and saliva.

Lithium ion adduction enables UPLC-MS/MS-based analysis of multi-class 3-hydroxyl group-containing keto-steroids

Steroids that contain a 3-hydroxyl group (3-OH steroids) are widely distributed in nature. During analysis with ESI-MS, they easily become dehydrated while in the protonated form, resulting in the production of several precursor ions and leading to low sensitivity of detection. To address this analytical challenge, here, we developed a method for the quantitation of 3-OH steroids by LC-MS/MS coupled with post-column addition of lithium (Li) ions to the mobile phase. The Li ion has a high affinity for the keto group of steroids, stabilizing their structures during ionization and permitting detection of analytes exclusively as the lithiated form. This not only improved the intensities of the precursor ions, but also promoted the formation of typical lithiated fragment ions. This improvement made the quantitation by multiple reaction monitoring more sensitive and reliable, as evidenced by 1.53-188 times enhanced detection sensitivity of 13 steroids that contained at least one keto and two hydroxyl groups or one keto and one 5-olefinic double bond, among 16 different 3-OH steroids. We deployed our newly developed method for profiling steroids in mouse brain tissue and identified six steroids in one tissue sample. Among these, 16-hydroxyestrone, tetrahydrocorticosterone, and 17α-hydroxypregnenolone were detected for the first time in the mouse brain. In summary, the method described here enables the detection of lithiated steroids by LC-MS/MS, including three 3-OH steroids not previously reported in the mouse brain. We anticipate that this new method may allow the determination of 3-OH steroids in different brain regions.

Development of a Validated UPLC-MS/MS Method for Analyzing Major Ginseng Saponins from Various Ginseng Species

Ginsenosides, which contain one triterpene and one or more sugar moieties, are the major bioactive compounds of ginseng. The aim of this study was to develop and optimize a specific and reliable ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the analysis of twelve different resources of ginseng. The six marker compounds of ginsenoside Rb₁, ginsenoside Rb₂, ginsenoside Rc, ginsenoside Rd, ginsenoside Re, and ginsenoside Rg₁, as well as an internal standard, were separated by a reversed-phase C-18 column with a gradient elution of water and methanol-acetonitrile. The multiple-reaction monitoring (MRM) mode was used to quantify and identify twelve market products. The results demonstrated that not only is the logarithm of its partition coefficient (cLog P; octanol-water partition coefficient) one of the factors, but also the number of sugars, position of sugars, and position of the hydroxyl groups are involved in the complicated separation factors for the analytes in the analytical system. If the amount of ginsenoside Rb₁ was higher than 40 mg/g, then the species might be Panax quinquefolius, based on the results of the marker ginsenoside contents of various varieties. In summary, this study provides a rapid and precise analytical method for identifying the various ginsenosides from different species, geographic environments, and cultivation cultures.

Identification of Six Phytochemical Compounds from Asparagus officinalis L. Root Cultivars from New Zealand and China Using UAE-SPE-UPLC-MS/MS: Effects of Extracts on H₂O₂-Induced Oxidative Stress

A simple, rapid, specific, and sensitive method was developed for the simultaneous identification and quantification of six major bioactive compounds, namely, caffeic acid, quercetin, apigenin, ferulic acid, baicalein, and kaempferol, from Asparagus officinalis roots (ARs) native to New Zealand (green and purple cultivars) and China (yellow, green, purple, and white cultivars) using ultrasound-assisted, solid-phase extraction (UASE-SPE) coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The method was validated in terms of linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy (expressed as recovery %), and precision (expressed as relative standard deviation (%RSD)). The retention times, ultraviolet visible (UV-vis) data, and mass spectral patterns of the detected peaks matched those of commercial standards, allowing characterization of the target compounds. The LODs and LOQs were 23 ng/mL and 70 ng/mL, 50 ng/mL and 150 ng/mL, 10 ng/mL and 30 ng/mL, 18 ng/mL and 54 ng/mL, 14.4 ng/mL and 43.6 ng/mL, and 7.5 ng/mL and 22.5 ng/mL for caffeic acid, quercetin, apigenin, ferulic acid, baicalein, and kaempferol, respectively, and the mean recovery rates were 85.8%, 73.0%, 90.2%, 80.6%, 76.7%, and 74.5% for the six compounds, respectively. The levels of the target compounds were significantly different (p < 0.05) among the six cultivars. The Chinese yellow AR had the highest levels of bioactive compounds: 6.0, 3.9, 0.4, 1.0, 0.86, and 0.8 mg/g for caffeic acid, quercetin, apigenin, ferulic acid, baicalein, and kaempferol, respectively. The AR extracts showed protective effects against oxidative stress in the HepG2 and L929 cell lines. The results indicate that AR extracts contain high flavonoid levels that provide protective functions against oxidative stress and support the potential commercial application of AR extracts.

Fast and simple determination of moroxydine residues in pig and chicken samples by ultra-performance liquid chromatography-tandem mass spectrometry

A general solid-phase extraction (SPE) method using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for the determination of moroxydine residues in pig and chicken samples has been developed. After extraction and purification of real samples, moroxydine residues were detected using a hydrophobic interaction liquid chromatography column with an optimised mobile phase composition. The extraction reagents, the kind of SPE columns and the type of eluents were optimised to achieve the maximum extraction efficiency. The matrix effects from the animal tissue influenced the quality of the quantitative data obtained. Under the optimised conditions, the moroxydine residues in pig and chicken samples spiked at three levels (1.0 μg/kg, 5.0 μg/kg and 10.0 μg/kg) were determined with good recoveries (61.5%-105.4%) and adequate relative standard deviations (3.2%-13.0%). In pig and chicken samples, the limit of detection (LOD) was 0.3 μg/kg, and the limit of quantification (LOQ) was 1.0 μg/kg. A sufficiently linear relationship in the range of 1.0 μg/kg-20.0 μg/kg was achieved with a good correlation coefficient (R² ≥ 0.99).

Pharmacokinetics of Schizandrin and Its Pharmaceutical Products Assessed Using a Validated LC-MS/MS Method

Schisandra chinensis has been used as an important component in various prescriptions in traditional Chinese medicine and, more recently, in Western-based medicine for its anti-hepatotoxic effect. The aim of this study was to develop a selective, rapid, and sensitive ultra-performance liquid chromatography-tandem mass spectrometry method for pharmacokinetic studies of schizandrin in rats. Liquid-liquid extraction was used for plasma sample preparation. A UHPLC reverse-phase C18e column (100 mm × 2.1 mm, 2 μm) coupled with a mobile phase of methanol-0.1% formic acid (85:15, v/v) was used for sample separation. A triple quadrupole tandem mass spectrometer was used to detect the analytes in the selected reaction monitoring mode. The linear range of schizandrin in rat plasma was 5.0–1000 ng/mL (r² > 0.999), with a lower limit of quantification of 5 ng/mL. The method was validated with regard to accuracy, intra-day and inter-day precision, linearity, stability, recovery, and matrix effects in rat plasma, which were acceptable according to the biological method validation guidelines developed by the FDA. This method was successfully applied to a pharmacokinetic study after oral administration of 3 g/kg and 10 g/kg of Schisandra chinensis products, which yielded a maximum concentration of schizandrin of 0.08 ± 0.07 and 0.15 ± 0.09 μg/mL, respectively. A parallel study design was used to investigate the oral bioavailability of single compound of schizandrin and the herbal extract, the single compound of pure schizandrin (10 mg/kg, i.v.), pure schizandrin (10 mg/kg, p.o.), and the herbal extract of Schisandra chinensis (3 g/kg and 10 g/kg, p.o.) were given individually. The dose of Schisandra chinensis (3 g/kg) equivalent to schizandrin (5.2 mg/kg); the dose of Schisandra chinensis (10 g/kg) equivalent to schizandrin (17.3 mg/kg). The result demonstrated that the oral bioavailability of schizandrin was approximately 15.56 ± 10.47% in rats, however the oral bioavailability of herbal extract was higher than single compound. The method was successfully applied to the pharmacokinetic study of pure schizandrin after oral administration of its pharmaceutical industry products in rats.

[Determination of 8 bisphenols in human breast milk by dansyl chloride derivatization-ultra performance liquid chromatography-tandem mass spectrometry]

OBJECTIVE

To establish a rapid and sensitive method for the analysis of eight bisphenols in breast milk using small amount of samples.

METHODS

Breast milk samples were extracted by acetonitrile and the lipid substances were removed by freezing under-20 ℃ condition. Then the samples were derivatized with dansyl chloride and analyzed by ultra-performance liquid chromatography-tandem mass spectrometry( UPLCMS/MS). The seperation was performed on an ACQUITY UPLC BEH Phenyl column( 2. 1 mm × 100 mm, 1. 7 μm) with methanol and 0. 1% formic acid in water as mobile phase. The electrospray source was in the positive ion mode and monitored in the multiple reactions monitoring mode. Isotope internal standard dilution technique was used for the quantification analysis. At last, the methodology was studied.

RESULTS

The linear range of 8 bisphenols was 0. 010-10. 00 μg/L. The recoveries of the three spiked levels were84. 6%-108. 1%, with the relative standard deviations no more than 12%( n = 6). 30 samples of breast milk were analyzed, in which BPA was detected in 11 breast milk samples, and the concentrations ranged from 0. 13 μg/L to 2. 25 μg/L. BPAF was detected in 1 breast milk sample, and the concentration was 0. 02 μg/L.

CONCLUSION

The established method using a small amount of breast milk is highly sensitive, simple and fast, and can be used for the simultaneous determination of 8 bisphenols in breast milk.

Measurement of serum 3-epi-25-hydroxyvitamin D3, 25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 in infant, paediatric and adolescent populations of Korea using ultra-performance liquid chromatography-tandem mass spectrometry

Background We evaluated the performance of ultra-performance liquid chromatography-tandem mass spectrometry to measure serum 3-epi-25-hydroxyvitamin D₃, 25-hydroxyvitamin D₃ and 25-hydroxyvitamin D₂ concentrations in 519 infant, paediatric and adolescent serum samples in Korea. Methods We used a Kinetex XB-C18 column and isocratic methanol/water (77.5/22.5, v/v) with 0.025% (v/v) high-performance liquid chromatography solvent additive flowing at 0.25 mL/min, yielding an 11 min/sample run time. A TQD triple quadrupole mass spectrometer in electrospray ionization positive ion mode with multiple reaction monitoring transition via an MSMS vitamin D kit was used to evaluate precision, carryover, ion suppression and linearity. Samples were prepared using the 4-phenyl-1,2,4-triazoline-3,5-dione derivatization method. Results Intra- and inter-run precisions were 1.23-13.28% and 1.02-10.08%, respectively. Group carryovers were -0.27% and 0.10%, respectively. There was no ion suppression. The calibration curve showed good linearity from calibrator Level 1 (11.75 nmol/L) to 6 (375 nmol/L) with R²> 0.9999. The 3-epi-25-hydroxyvitamin D₃ and 25-hydroxyvitamin D₃ peaks were clearly separated in the extracted ion chromatogram. Infant serum samples 3-epi-25-hydroxyvitamin D₃ concentrations were significantly higher than paediatric and adolescent concentrations. Conclusions The ultra-performance liquid chromatography-tandem mass spectrometry assay performed acceptably, clearly separating 3-epi-25-hydroxyvitamin D₃ from 25-hydroxyvitamin D₃. High 3-epi-25-hydroxyvitamin D₃ concentrations were observed in infant but not in paediatric and adolescent serum samples.

High-throughput analysis of sulfatides in cerebrospinal fluid using automated extraction and UPLC-MS/MS

Sulfatides (STs) are a group of glycosphingolipids that are highly expressed in brain. Due to their importance for normal brain function and their potential involvement in neurological diseases, development of accurate and sensitive methods for their determination is needed. Here we describe a high-throughput oriented and quantitative method for the determination of STs in cerebrospinal fluid (CSF). The STs were extracted using a fully automated liquid/liquid extraction method and quantified using ultra-performance liquid chromatography coupled to tandem mass spectrometry. With the high sensitivity of the developed method, quantification of 20 ST species from only 100 μl of CSF was performed. Validation of the method showed that the STs were extracted with high recovery (90%) and could be determined with low inter- and intra-day variation. Our method was applied to a patient cohort of subjects with an Alzheimer's disease biomarker profile. Although the total ST levels were unaltered compared with an age-matched control group, we show that the ratio of hydroxylated/nonhydroxylated STs was increased in the patient cohort. In conclusion, we believe that the fast, sensitive, and accurate method described in this study is a powerful new tool for the determination of STs in clinical as well as preclinical settings.

[UPLC-MS / MS for the pharmacokinetics of icariin in rats]

OBJECTIVE

To establish an ultra-performance liquid chromatographytandem mass spectrometry( UPLC-MS / MS) method for the quantification of icariin( ICA), and investigate pharmacokinetics of ICA in rats following multiple oral administration.

METHODS

ICA and an internal standard coumestrol( CMT) were extracted from rat plasma using ethyl acetate and separated on a BEH C18( 50 mm × 2. 1mm, 1. 7 μm) column using a gradient mobile phase of acetonitrile containing 0. 1%( V / V)formic acid and water containing 2 mmol / L ammonium formate at a flow rate of 0. 3m L / min. In negative electrospray ionization mode, multiple reaction monitoring of the precursor-product ion transitions of m / z 675. 6→351. 1 for ICA, 267. 0 →211. 1 for CMT was used for the quantification. Plasma was collected after rats were orally administered with ICA at multiple doses of 50 mg / kg.

RESULTS

The linear calibration curve was achieved in a concentration range of 0. 5-50 ng / m L with a lower limit of quantification of0. 5 ng / m L. The value of intra- and inter-day precision was less than 11. 3% and accuracy fell in the ranges of 94. 3%-98. 7%. The recovery ranged from 81. 3% to85. 2% and the matrix effects from 94. 3% to 103. 2%. After oral administration of ICA to rats, t1 /2was( 1. 68 ± 0. 29) h, Cmaxwas( 29. 6 ± 5. 3) ng / m L, tmaxwas( 1. 00 ± 0. 00) h, AUC0- twas( 88. 4 ± 13. 9)( h·ng) / m L.

CONCLUSION

The method is specific and accurate, suitable for preclinical pharmacokinetics of ICA.

Atorvastatin induces bile acid-synthetic enzyme Cyp7a1 by suppressing FXR signaling in both liver and intestine in mice

Statins are effective cholesterol-lowering drugs to treat CVDs. Bile acids (BAs), the end products of cholesterol metabolism in the liver, are important nutrient and energy regulators. The present study aims to investigate how statins affect BA homeostasis in the enterohepatic circulation. Male C57BL/6 mice were treated with atorvastatin (100 mg/kg/day po) for 1 week, followed by BA profiling by ultra-performance LC-MS/MS. Atorvastatin decreased BA pool size, mainly due to less BA in the intestine. Surprisingly, atorvastatin did not alter total BAs in the serum or liver. Atorvastatin increased the ratio of 12α-OH/non12α-OH BAs. Atorvastatin increased the mRNAs of the BA-synthetic enzymes cholesterol 7α-hydroxylase (Cyp7a1) (over 10-fold) and cytochrome P450 27a1, the BA uptake transporters Na⁺/taurocholate cotransporting polypeptide and organic anion transporting polypeptide 1b2, and the efflux transporter multidrug resistance-associated protein 2 in the liver. Noticeably, atorvastatin suppressed the expression of BA nuclear receptor farnesoid X receptor (FXR) target genes, namely small heterodimer partner (liver) and fibroblast growth factor 15 (ileum). Furthermore, atorvastatin increased the mRNAs of the organic cation uptake transporter 1 and cholesterol efflux transporters Abcg5 and Abcg8 in the liver. The increased expression of BA-synthetic enzymes and BA transporters appear to be a compensatory response to maintain BA homeostasis after atorvastatin treatment. The Cyp7a1 induction by atorvastatin appears to be due to suppressed FXR signaling in both the liver and intestine.

A study of the dexamethasone sodium phosphate release properties from a periocular capsular drug delivery system

The aim of this study was to investigate whether a periocular capsular drug delivery system (DDS) can release dexamethasone sodium phosphate (DEXP) in vitro and in vivo to the posterior segment of rabbit's eye. In vitro, the periocular capsular DDS containing 2 mg/ml or 5 mg/ml DEXP was immersed in modified Franz diffusion cell. Four-hundred microliters of liquid was aspirated at 0.5, 1, 2, 4, 8, 24 and 48 h for determination. In vivo, the DEXP-filled periocular capsular DDS was implanted into the sub-Tenon's sac of the New Zealand rabbit. DEXP concentration at the serum aqueous humor, cornea, iris, lens, ciliary body, vitreous, retina, choroids and sclera was quantified at 1, 3, 7, 14, 28 and 56 d after implantation. The DEXP concentration was determined by ultra-performance liquid chromatography-tandem mass spectrometry. In vitro, the periocular capsular DDS released the DEXP in time-dependent manner from 1/2 to 48 h. In vivo, the concentrations of the DEXP at the retina, choroids, ciliary body and iris were 123.11 (91.23, 732.61) ng/g, 362.46 ± 330.46 ng/g, 71.64 (71.35, 180.21) ng/g and 192.50 ± 42.66 ng/g, respectively, at 56 d after implantation. Minimal DEXP was found in the aqueous, serum and vitreous. Our results demonstrated that DEXP could be sustained released from the periocular capsular DDS, which indicated that the periocular capsular DDS might be a potential candidate of transscleral drug delivery for the management of posterior segment diseases.

Increased bile acids in enterohepatic circulation by short-term calorie restriction in male mice

Previous studies showed glucose and insulin signaling can regulate bile acid (BA) metabolism during fasting or feeding. However, limited knowledge is available on the effect of calorie restriction (CR), a well-known anti-aging intervention, on BA homeostasis. To address this, the present study utilized a "dose-response" model of CR, where male C57BL/6 mice were fed 0, 15, 30, or 40% CR diets for one month, followed by BA profiling in various compartments of the enterohepatic circulation by UPLC-MS/MS technique. This study showed that 40% CR increased the BA pool size (162%) as well as total BAs in serum, gallbladder, and small intestinal contents. In addition, CR "dose-dependently" increased the concentrations of tauro-cholic acid (TCA) and many secondary BAs (produced by intestinal bacteria) in serum, such as tauro-deoxycholic acid (TDCA), DCA, lithocholic acid, ω-muricholic acid (ωMCA), and hyodeoxycholic acid. Notably, 40% CR increased TDCA by over 1000% (serum, liver, and gallbladder). Interestingly, 40% CR increased the proportion of 12α-hydroxylated BAs (CA and DCA), which correlated with improved glucose tolerance and lipid parameters. The CR-induced increase in BAs correlated with increased expression of BA-synthetic (Cyp7a1) and conjugating enzymes (BAL), and the ileal BA-binding protein (Ibabp). These results suggest that CR increases BAs in male mice possibly through orchestrated increases in BA synthesis and conjugation in liver as well as intracellular transport in ileum.