Journal of Chromatography B (v.988, #C)

Ginkgolide K (GK), a derivative compound of ginkgolide B, has been recently isolated from the leaves of Ginkgo biloba. It is a powerful natural platelet activate factor (PAF) antagonist, and also has obvious protect effects for cerebral ischemia. However, no reports have been described for the pharmacokinetic study of GK. In this study, a simple, sensitive and reliable ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method has been developed for the determination of GK in rat plasma and tissues. Biological samples were pretreated by an efficient liquid–liquid extraction with ethyl acetate. The chromatographic separation was achieved on an Agilent ZORBAX SB-Aq column (4.6 mm × 50 mm, 1.8 μm) with a mobile phase of 0.5% aqueous formic acid (A)–menthol (B). Quantitation was carried out on a triple quadruple mass spectrometry using positive electrospray ionization in multiple reaction monitoring mode. Diazepam was used as internal standard (IS). The ion transitions monitored were set at m/z 407.10 → 389.20 and m/z 285.08 → 193.10 for GK and IS, respectively. The developed method was fully validated and successfully applied to the pharmacokinetics and tissue distribution study of GK after intravenous administration. The current results have indicated that pharmacokinetic parameters of GK vary in a dose-dependent manner with rapid elimination in 4 h. The major distribution tissues of GK in rats were liver and kidney. This study would provide critical information to promote the future study of GK.
Keywords: Ginkgo; Ginkgolide K; Pharmacokinetics; Tissue distribution; UHPLC-MS/MS;

A simple, sensitive and reliable gradient elution high performance liquid chromatography electrospray ionization mass spectrometry (HPLC–ESI-MS) method was developed for quantifying helicid in dog plasma. The limit of detection (LOD) and the lower limit of quantitation (LLOQ) were 0.3 and 1 ng/mL, respectively. This method was validated for selectivity, linearity, accuracy and precision, extraction recoveries, matrix effects, carry-over, cross-talk, dilution integrity, stability and incurred sample reanalysis (ISR). Bioavailability and pharmacokinetic parameters of helicid in beagle dogs were researched from a two period crossover design study. After intravenous administration (i.v.), helicid had a mean (±SD) AUC0–∞ of 12062.06 ± 2482.69 ng/mL h and terminal half-life (t 1/2z ) of 2.91 ± 1.37 h, while C max was 35613.23 ± 8157.18 ng/mL. Following intragastric gavage administration (i.g.), AUC0–∞ was 7589.16 ± 1797.20 ng/mL h along with a longer t 1/2z of 4.10 ± 4.35 h. C max was researched at 0.58 ± 0.20 h. The absolute bioavailability (F) of helicid was 15.74 ± 1.87%.
Keywords: Helicid; HPLC–ESI-MS; Pharmacokinetics; Bioavailability;

In vitro evaluation of Sun Protection Factor and stability of commercial sunscreens using mass spectrometry by Diogo Noin de Oliveira; Jeany Delafiori; Mônica Siqueira Ferreira; Rodrigo Ramos Catharino (13-19).
Sunlight exposure causes several types of injury to humans, especially on the skin; among the most common harmful effects due to ultraviolet (UV) exposure are erythema, pigmentation and lesions in DNA, which may lead to cancer. These long-term effects are minimized with the use of sunscreens, a class of cosmetic products that contains UV filters as the main component in the formulation; such molecules can absorb, reflect or diffuse UV rays, and can be used alone or as a combination to broaden the protection on different wavelengths. Currently, worldwide regulatory agencies define which ingredients and what quantities must be used in each country, and enforce companies to conduct tests that confirm the Sun Protection Factor (SPF) and the UVA (Ultraviolet A) factor. Standard SPF determination tests are currently conducted in vivo, using human subjects. In an industrial mindset, apart from economic and ethical reasons, the introduction of an in vitro method emerges as an interesting alternative by reducing risks associated to UV exposure on tests, as well as providing assertive analytical results. The present work aims to describe a novel methodology for SPF determination directly from sunscreen formulations using the previously described cosmetomics platform and mass spectrometry as the analytical methods of choice.
Keywords: Sunscreens; Sun Protection Factor; Cosmetomics; In vitro testing; Bemotrizinol;

Development of a solvent-free analytical method for paracetamol quantitative determination in Blood Brain Barrier in vitro model by Marie-Hélène Langlois; Antonios Vekris; Christine Bousses; Elodie Mordelet; Nathalie Buhannic; Céline Séguard; Pierre-Olivier Couraud; Babette B. Weksler; Klaus G. Petry; Karen Gaudin (20-24).
A Reversed Phase-High Performance Liquid Chromatography/Diode Array Detection method was developed and validated for paracetamol quantification in cell culture fluid from an in vitro Blood Brain Barrier model. The chromatographic method and sample preparation were developed using only aqueous solvents. The column was a XTerra RP18 150 × 4.6 mm, 3.5 μm with a guard column XTerra RP18 20 × 4.6 mm, 3.5 μm at 35 °C and the mobile phase was composed by 100% formate buffer 20 mM at pH 4 and flow rate was set at 1 mL/min. The detection was at 242 nm. The sample was injected at 10 μL. Validation was performed using the accuracy profile approach. The analytical procedure was validated with the acceptance limits at ±10% over a range of concentration from 1 to 58 mg L−1. The procedure was then used in routine to determine paracetamol concentration in a brain blood barrier in vitro model. Application of the Unither paracetamol formulation in Blood Brain Barrier model allowed the determination and comparison of the transcellular passage of paracetamol at 37 °C and 4 °C, that excludes paracellular or non specific leakage.
Keywords: Paracetamol; RP-HPLC; Solvent free; Accuracy profile; Blood Brain Barrier in vitro model; Acetaminophen;

On-line solid-phase extraction (SPE) is becoming an increasingly widespread technique in the clean-up of complex matrices such as body fluids, prior to chromatographic analysis. The use of small SPE columns instead of disposable SPE cartridges allows multiple injections and complete automation. In addition, it decreases the cost of consumables and improves the quality of the overall analysis. Coupling of SPE with HPLC combines sample preparation and separation in one system. In this paper a validated on-line multidimensional (MD) SPE-LC–MS/MS method is described for the determination of Tetrandrine (model drug) in human blood samples. The developed method showed the applicability of direct injection of plasma samples to an on-line MD-SPE-LC–MS/MS system to determine small molecules i.e. drugs. The experimental design is unique. Quantification was through tandem mass spectrometry with positive electrospray ionization (ESI) and multiple reactions monitoring (MRM). The limit of detection was calculated as 31.98 ng/mL. The linear range of the method was between 40.0 and 800.0 ng/mL. Pharmacokinetic parameters are usually determined by analysis of drug concentrations in plasma rather than whole blood. Parameters determined using plasma data may be misleading if concentrations of drug differ between plasma and red blood cells. We successfully applied the developed method for the determination of the distribution coefficient of the model drug Tetrandrine between human red blood cells and blood plasma proteins. The determination of distribution coefficient study results demonstrated that the developed method can provide direct and accurate measurement of RBC partitioning in a model drug and could be applied for screening of other compounds for potential high RBC partition, predicting potential drug toxicity and investigating mechanisms associated with RBC partitions.
Keywords: On-line SPE; Tandem mass spectrometry; Column switching; Body fluids; Distribution coefficient; Cell-disintegrated blood;

An LC–MS/MS method was developed for simultaneous analysis of puerarin, daidzin, baicalin, glycyrrhizic acid, liquiritin, berberine, palmatine and jateorhizine of Gegenqinlian Decoction (GQD) and active components alignment (ACA) in rat plasma using hesperidin as the internal standard (I.S.). Chromatography was performed using a C18 column, with gradient elution with 1% acetic acid–0.001 mol/L ammonium acetate and acetonitrile at 0.2 ml/min. All analytes including I.S. were monitored under positive ionization conditions by selected reaction monitoring with an electrospray ionization source. The optimized mass transition ion-pairs (m/z) for quantitation were 471/297 for puerarin, 471/255 for daidzin, 447/271 for baicalin, 823/453 for glycyrrhizic acid, 419/257 for liquiritin, 336/320 for berberine, 352/336 for palmatine, 338/322 for jateorhizine and 611/303 for hesperidin. The calibration curves were linear over the concentration ranges from 0.15–63.0 to 6.3–6340.0 ng/mL. Intra-day and inter-day precisions (RSD%) were within 15.0%, and accuracy (RE%) ranged from −7.4 to 13.2%. The extraction recoveries were ranged from 60.4 to 93.3%. The proposed method was further applied to compare the pharmacokinetics of all analytes following a single oral administration of GQD and ACA. In conclusion, the eight analytes of GQD and ACA had partly similar pharmacokinetics, which were different from single composition (such as puerarin).
Keywords: LC–MS/MS; Gegenqinlian decoction (GQD); Active components alignment (ACA); Pharmacokinetics; Puerarin;

A novel dereplication strategy for the identification of two new trace compounds in the extract of Gastrodia elata using UHPLC/Q-TOF-MS/MS by Zhifeng Li; Yawei Wang; Hui Ouyang; Yu Lu; Yan Qiu; Yulin Feng; Hongliang Jiang; Xin Zhou; Shilin Yang (45-52).
An ultra performance liquid chromatography (UHPLC) coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS/MS) was used in the structural determination of natural compounds in Gastrodia elata. A total of 64 compounds were identified or tentatively characterized. The strategy used for characterization was comparing their retention time and fragmentation behaviors with those of the reference standards, or investigating their accurate mass measurements and characteristic fragmentation patterns followed by low-energy collision dissociation tandem mass spectrometry (CID-MS/MS). Phenolic conjugates mainly underwent consecutive losses of gastrodin residues and combined losses of H2O and CO2 from their citric acid units under negative MS/MS conditions. According to these rules, we have successfully characterized fifteen potential novel compounds. To confirm the reliability of this strategy, two targeted unknown trace parishins were obtained from G. elata by LC/MS-guided isolation. Based on the analysis of data from NMR spectroscopy and other techniques, the two unknown parishins were identified as 2-[4-O-(β-d-glucopyranosyl)benzyl]-3-methyl-citrate (parishin J) and 1,2-di-[4-O-(β-d-glucopyranosyl)benzyl]-3-methyl-citrate (parishin K), respectively. The fully established structures were consistent with the MS-oriented structural elucidation. This study expanded our knowledge on parishins in Gastrodia species, and the proposed strategy was proven efficient and reliable in the discovery of new minor compounds from herbal extracts.
Keywords: Gastrodia elata; Parishin; Q-TOF-MS/MS;

Systematic profiling of indole-3-acetic acid biosynthesis in bacteria using LC–MS/MS by Guang-Huey Lin; Chung -Yu Chang; Huei-Ru Lin (53-58).
Indole-3-acetic acid (IAA) is produced from tryptophan through five synthesis pathways. A comprehensive method for the quantification of IAA and biosynthesis-related intermediates in a culture medium was developed. Sample preparation was simple with protein precipitation. The analytes were separated on a superficially porous C18 silica column and detected by electrospray ionization-tandem mass spectrometry in the positive ion multiple reaction monitoring mode. The limit of detection was 0.05 μM, and the lower limits of quantification ranged from 0.05 to 2 μM. The intra-day and inter-day precision and accuracy were less than 13.96%. Ion suppression was observed, and the deuterated internal standards were used to compensate for the matrix effect. The method was applied to analyze changes in tryptophan catabolism in a culture medium of Pseudomonas putida. The proposed method is robust and suitable for the systematic profiling of IAA biosynthesis in culture supernatant.
Keywords: Indole-3-acetic acid; Liquid chromatography–tandem mass spectrometry; IAA biosynthesis; Tryptophan;

A sensitive and versatile, ultra-high performance, liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method coupled to pre-column derivatization for the simultaneous determination of 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), dopamine (DA), norepinephrine (NE), homovanillic acid (HVA), γ-aminobutyric acid (GABA) and glutamic acid (Glu) was developed and validated in rat plasma. The analytes were dansylated under strong alkaline conditions after protein precipitation extraction, which were analyzed on a BEH C18 column using a gradient elution. The lower limit of quantification (LLOQ) values for 5-HT, 5-HIAA, DA, NE, HVA, GABA and Glu were 1.00, 1.00, 0.991, 0.992, 1.02, 1000, and 5030 pmol/mL, respectively. Good linearity was obtained (r  > 0.99) and the intra- and inter-day precisions of the method (relative standard deviation, RSD%) were lower than 12%. The method was novel, sensitive and specific which can provide an alternative method for the quantification of neurotransmitters and their metabolites in plasma samples.
Keywords: Monoamine neurotransmitters; Tandem mass spectrometry; Biomarker; Fluoxetine;

“Center punch” and “whole spot” bioanalysis of apixaban in human dried blood spot samples by UHPLC-MS/MS by Naiyu Zheng; Long Yuan; Qin C. Ji; Heidi Mangus; Yan Song; Charles Frost; Jianing Zeng; Anne-Françoise Aubry; Mark E. Arnold (66-74).
Apixaban (Eliquis™) was developed by Bristol-Myers Squibb (BMS) and Pfizer to use as an antithrombotic/anticoagulant agent and has been recently approved for the prevention of stroke and systemic embolism in patients with nonvalvular atrial fibrillation. A clinical study of apixaban, sponsored by BMS and Pfizer, included a pilot exploratory portion to evaluate the potential for future drug concentration monitoring using dried blood spot (DBS) sample collection. For DBS sample collection, a fixed blood volume was dispensed onto a DBS card by either regular volumetric pipette (venous blood collection) or capillary dispenser (finger prick blood collection). A 96-well semi-automated liquid–liquid extraction sample preparation procedure was developed to provide clean extracts for UHPLC–MS/MS quantitation. Assays using both partial-spot center punch and whole spot punch were developed and validated. The linear dynamic ranges for all the analyses were from 0.5 to 500 ng/mL. The coefficient of determination (r 2) values was >0.9944 for all the validation runs. For the center punch approach, the intra-assay precision (%CV) was within 4.4% and inter-assay precision was within 2.6%. The assay accuracy, expressed as %Dev., was within ±5.4% of the nominal concentrations. One accuracy and precision run was performed using the whole spot approach, the intra-assay precision (%CV) was within 7.1% and the accuracy was within ±8.0% of the nominal concentrations. In contrast to the center punch approach, the whole spot approach eliminated the effect of hematocrit and high lipids on the analysis of apixaban in human DBS when an accurate sample blood volume was collected on DBS cards.
Keywords: Dried blood spot; Whole spot punch; Hematocrit effect; Liquid–liquid extraction; UHPLC–MS/MS;

Application of a liquid chromatographic/tandem mass spectrometric method to a urinary excretion study of rabeprazole and two of its metabolites in healthy human urine by Chengtao Lu; Yanyan Jia; Ying Song; Xueqing Li; Yuan Sun; Jinyi Zhao; Shan Wang; Lei Shi; Aidong Wen; Li Ding (75-80).
To study urinary excretion properties of rabeprazole and two of its metabolites, i.e. rabeprazole thioether and desmethyl rabeprazole thioether in human urine, a sensitive, selective, accurate and precise method for the quantification of rabeprazole and two of its metabolites using a liquid chromatographic/tandem mass spectrometric method has been developed and validated. Starting with a 200 μL urine aliquot, a general sample preparation was performed using protein precipitation with methanol. Analytes were separated on a Dikma Inspire™ C18 column (150 mm × 2.1 mm, 5 μm) using a mixture of methanol and aqueous 10 mM ammonium acetate buffer containing 0.05% formic acid (55:45, v/v) as mobile phase. Linearity was obtained over the concentration range of 0.1446–96.38 ng/mL, 0.3198–319.8 ng/mL and 0.05160–82.53 ng/mL for rabeprazole, rabeprazole thioether, desmethyl rabeprazole thioether in human urine, respectively. The fully validated method was applied to a urine excretion study of rabeprazole sodium administered as a 30 min intravenous infusion for the first time. The calculated cumulative urinary recovery just reached 0.04745‰, 1.272‰ and 0.1631‰ of dose within 24 h post-dose for rabeprazole, rabeprazole thioether, and desmethyl rabeprazole thioether, respectively, after intravenous infusion administration, indicating that rabeprazole and its two main metabolites undergo substantial non-renal elimination in healthy Chinese volunteers.
Keywords: LC–MS/MS; Rabeprazole; Rabeprazole thioether; Desmethyl rabeprazole thioether; Pharmacokinetics;

Development and validation of a liquid chromatography tandem mass spectrometry assay for the quantitation of a protein therapeutic in cynomolgus monkey serum by Yue Zhao; Guowen Liu; Aida Angeles; Lora L. Hamuro; Kevin J. Trouba; Bonnie Wang; Renuka C. Pillutla; Binodh S. DeSilva; Mark E. Arnold; Jim X. Shen (81-87).
We have developed and fully validated a fast and simple LC-MS/MS assay to quantitate a therapeutic protein BMS-A in cynomolgus monkey serum. Prior to trypsin digestion, a recently reported sample pretreatment method was applied to remove more than 95% of the total serum albumin and denature the proteins in the serum sample. The pretreatment procedure simplified the biological sample prior to digestion, improved digestion efficiency and reproducibility, and did not require reduction and alkylation. The denatured proteins were then digested with trypsin at 60 °C for 30 min and the tryptic peptides were chromatographically separated on an Acquity CSH column (2.1 mm × 50 mm, 1.7 μm) using gradient elution. One surrogate peptide was used for quantitation and another surrogate peptide was selected for confirmation. Two corresponding stable isotope labeled peptides were used to compensate variations during LC-MS detection. The linear analytical range of the assay was 0.50–500 μg/mL. The accuracy (%Dev) was within ±5.4% and the total assay variation (%CV) was less than 12.0% for sample analysis. The validated method demonstrated good accuracy and precision and the application of the innovative albumin removal sample pretreatment method improved both assay sensitivity and robustness. The assay has been applied to a cynomolgus monkey toxicology study and the serum sample concentration data were in good agreement with data generated using a quantitative ligand-binding assay (LBA). The use of a confirmatory peptide, in addition to the quantitation peptide, ensured the integrity of the drug concentrations measured by the method.
Keywords: LC-MS/MS; Protein therapeutics; Bioanalysis; Albumin removal; Validation;

Development and validation of an ultra-high performance liquid chromatography–tandem mass spectrometry method to measure creatinine in human urine by S. Fraselle; K. De Cremer; W. Coucke; G. Glorieux; J. Vanmassenhove; E. Schepers; N. Neirynck; I. Van Overmeire; J. Van Loco; W. Van Biesen; R. Vanholder (88-97).
Despite decades of creatinine measurement in biological fluids using a large variety of analytical methods, an accurate determination of this compound remains challenging. Especially with the novel trend to assess biomarkers on large sample sets preserved in biobanks, a simple and fast method that could cope with both a high sample throughput and a low volume of sample is still of interest. In answer to these challenges, a fast and accurate ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method was developed to measure creatinine in small volumes of human urine. In this method, urine samples are simply diluted with a basic mobile phase and injected directly under positive electrospray ionization (ESI) conditions, without further purification steps. The combination of an important diluting factor (104 times) due to the use of a very sensitive triple quadrupole mass spectrometer (XEVO TQ) and the addition of creatinine-d3 as internal standard completely eliminates matrix effects coming from the urine. The method was validated in-house in 2012 according to the EMA guideline on bioanalytical method validation using Certified Reference samples from the German External Quality Assessment Scheme (G-Equas) proficiency test. All obtained results for accuracy and recovery are within the authorized tolerance ranges defined by G-Equas. The method is linear between 0 and 5 g/L, with LOD and LOQ of 5 × 10−3  g/L and 10−2  g/L, respectively. The repeatability (CVr  = 1.03–2.07%) and intra-laboratory reproducibility (CVRW  = 1.97–2.40%) satisfy the EMA 2012 guideline. The validated method was firstly applied to perform the German G-Equas proficiency test rounds 51 and 53, in 2013 and 2014, respectively. The obtained results were again all within the accepted tolerance ranges and very close to the reference values defined by the organizers of the proficiency test scheme, demonstrating an excellent accuracy of the developed method. The method was finally applied to measure the creatinine concentration in 210 urine samples, coming from 190 patients with a chronic kidney disease (CKD) and 20 healthy subjects. The obtained creatinine concentrations (ranging from 0.12 g/L up to 3.84 g/L) were compared, by means of a Passing Bablok regression, with the creatinine contents obtained for the same samples measured using a traditional compensated Jaffé method. The UHPLC–MS/MS method described in this paper can be used to normalize the concentration of biomarkers in urine for the extent of dilution.
Keywords: Creatinine; Urine; UHPLC–MS/MS; Isotope dilution; Method validation; Chronic kidney disease (CKD);

High-throughput batch screening technologies have become an important tool in downstream process development. Although continuative miniaturization saves time and sample consumption, there is yet no screening process described in the 384-well microplate format. Several processes are established in the 96-well dimension to investigate protein–adsorbent interactions, utilizing between 6.8 and 50 μL resin per well. However, as sample consumption scales with resin volumes and throughput scales with experiments per microplate, they are limited in costs and saved time. In this work, a new method for in-well resin quantification by optical means, applicable in the 384-well format, and resin volumes as small as 0.1 μL is introduced. A HTS batch isotherm process is described, utilizing this new method in combination with optical sample volume quantification for screening of isotherm parameters in 384-well microplates. Results are qualified by confidence bounds determined by bootstrap analysis and a comprehensive Monte Carlo study of error propagation. This new approach opens the door to a variety of screening processes in the 384-well format on HTS stations, higher quality screening data and an increase in throughput.
Keywords: High-throughput screening (HTS); Resin quantification; Batch isotherm; Liquid handling station (LHS); Monte Carlo; Bootstrap analysis;

High performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) for the sensitive determination of hyaluronan oligosaccharides by Martin Rothenhöfer; Marco Grundmann; Günther Bernhardt; Frank-Michael Matysik; Armin Buschauer (106-115).
High performance anion exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) was optimized for the analysis of oligosaccharides derived from the extracellular matrix component hyaluronan. Using this sensitive approach, the separation of oligosaccharides consisting of two (molecular weight ca. 0.8 kDa) up to 25–30 (molecular weight: ca. 9.5–11.4 kDa) disaccharide moieties was possible. Standard oligosaccharides (comprising 2–4 repetitive disaccharides) were detectable at very low amounts of 0.2–0.3 pmol (20–30 nM). Including 10 min of column equilibration, a complex mixture of low molecular weight hyaluronan can be analyzed within 40 min. The HPAEC method was successfully applied to the study of the size-dependency of both the action of bovine testicular hyaluronidase (BTH) and the precipitation of hyaluronan by cetyltrimethylammonium bromide (CTAB), a physicochemical reaction often used for the determination of hyaluronan and hyaluronidase activity.
Keywords: Bovine testicular hyaluronidase; Capillary electrophoresis; High performance anion exchange chromatography; Hyaluronan oligosaccharides; Pulsed amperometric detection; Turbidimetric hyaluronidase assay;

Liquid–liquid extraction and liquid chromatography–mass spectrometry detection of curcuminoids from bacterial culture medium by Suryani Tan; Thusitha W.T. Rupasinghe; Dedreia L. Tull; Mary Ann Augustin; Sally L. Gras (116-120).
Liquid chromatography–mass spectrometry (LC–MS) has been used to detect polyphenolic curcuminoids found in turmeric but studies of metabolism by bacterial and mammalian cells in vitro are compromised by poor recovery from the culture medium. We report a liquid–liquid extraction procedure with ethyl acetate and use LC–MS to quantify extracted curcuminoids. Ethyl acetate allows recoveries of ∼80–86% of curcuminoids from the bacterial growth medium, bacterial cell lysate and combined bacterial cell and growth medium matrices; a clear improvement over acetonitrile where recoveries were ∼25–66%. This optimised method will enable studies of curcuminoid metabolism and may be applicable to other hydrophobic polyphenolic compounds.
Keywords: Curcumin; LC–MS; Curcuminoids; Ethyl acetate; Recovery; Cell medium;

The increasing availability of liquid chromatography tandem mass spectrometry (LC–MS/MS) in clinical laboratories provides the opportunity to replace or complement present underperforming immuno- and chemometric assays. Amylase and lipase show limited specificity and sensitivity for pancreatic inflammation and lack the capacity of monitoring the disease due to their short half-lives. Previous findings suggested that cleavage products of the pancreatic enzyme carboxypeptidase A could be a more suitable indicator for defining and classifying pancreatic inflammation. The plasma proteins albumin and β-fibrinogen were digested with trypsin and truncated forms (des-Leu-albumin, and des-Gln-β-fibrinogen) quantified against their non-truncated forms by LC–MS/MS. Four hundred fifty eight samples from 83 patients were used to evaluate the novel method and affirm its suitability for detecting acute pancreatitis. A robust, selective, precise and accurate LC–MS/MS method was set up to measure the proportion of truncated proteins. Reference ranges for the proportion of the truncated albumin and β-fibrinogen were from 2% to 9% and 3% to 25%, respectively. Acute pancreatitis patients had values above these ranges and were distinctly separated from reference control individuals. The longer circulating half-lives of albumin and fibrinogen compared to pancreatic enzymes themselves provide the potential to diagnose pancreatitis more specifically over a longer time period, to monitor the course of the disease, and to track recurrent complications. The wide range of the proportion and the differential half-life of both truncated proteins could also be used for assessing the severity of pancreatitis.
Keywords: Mass spectrometry; LC–MS/MS; Pancreatitis; Albumin; Fibrinogen; Tryptic digest;

A method of using high-speed counter-current chromatography (HSCCC) for preparative isolation and purification of oligostilbenes from the ethanol extracts of seed kernel of Iris lactea Pall. var. chinensis (Fisch.) Koidz was established in this study. Four oligostilbenes were successfully separated and purified by HSCCC with two sets of two-phase solvent system, n-hexane-ethyl acetate-methanol-water (3:6:4.2:5.5, v/v/v/v) in the head-to-tail elution mode for the first separation to mainly isolate vitisin A (58 mg), ɛ-viniferin (76 mg) and peak II (43 mg) from 300 mg of the crude ethanol extracts, and then light petroleum–ethyl acetate–methanol–water (5:5:3:6, v/v/v/v) in the tail-to-head elution mode for the second separation to isolate vitisin B (52 mg) and vitisin C (11 mg) from 100 mg of peak II. The purities of the isolated four oligostilbenes were all over 95.0% as determined by HPLC. Vitisin A, vitisin B and vitisin C, resveratrol tetramers, were isolated from Iris lactea for the first time. The preparation of crude sample was simple and the HSCCC method for the isolation and purification of four oligostilbenes was rapid, efficient and economical.
Keywords: HSCCC; Iris lactea; Oligostilbenes; Preparation;

Zhi-Zi-Hou-Po decoction (ZZHPD), a traditional Chinese medicine (TCM) formula, has been used for treatment of depressive-like symptoms for centuries. However, studies of its antidepressant effect and mechanism are challenging, owing to the complex pathophysiology of depression and complexity of ZZHPD with multiple constituents acting on different metabolic pathways. The present study was designed to develop a liquid chromatography-mass spectrometry (LC-MS) method for simultaneous determination of depression biomarkers: tryptophan (Trp), phenylalanine (Phe), tyrosine (Tyr), indole-3-acetic acid (IAA), hippuric acid (HA), phenaceturic acid (PA), creatinine (Cr), glutamic acid (Glu), succinic acid (SA) and γ-aminobutyric acid (GABA), as well as to study the antidepressant effect and potential mechanism of ZZHPD based on holistic view of an organism. The analysis was performed on a CAPCELL PAK C18 column with methanol and 0.01% formic acid in water using gradient elution. The method showed a good linearity (r 2  > 0.99) with the other validation parameters were within acceptance range. The results demonstrated Trp, Phe, Tyr, IAA, HA, Cr, Glu and SA levels were significant lower in model group, while PA and GABA were significant higher than those in control group. The rats with ZZHPD treatment showed a tendency of bringing the levels of all these biomarkers to normal except Cr and Glu. It could be a powerful manner to provide mechanistic insights into the therapeutic effects of complex prescriptions and further understand pathophysiology of depression to assist in clinical diagnosis.
Keywords: Chronic unpredictable mild stress; Depression biomarkers; Liquid chromatography-mass spectrometry; Zhi-Zi-Hou-Po decoction; Rat plasma;

An ultra-performance convergence chromatography (UPC2) system coupled tandem mass spectrometry was successfully utilised to analyse chlormadinone acetate, delmadinone acetate, fluorogestone acetate, medroxyprogesterone acetate, megestrol acetate, melengestrol acetate, chlortestasterone acetate in bovine and porcine kidney fat. This novel approach obtained an improved resolution in comparison to previously reported chromatographic methods combined with MS detector in a shorter analytical time. All the acetylgestagen compounds were well separated on a ACQUITY UPC2 HSS C18 column (3.0 × 100 mm, 1.7 μm) by applying methanol and carbon dioxide (2/98). The LOQ of delmadinone acetate, melengestrol acetate, medroxyprogesterone acetate and megestrol acetate are 0.5 μg/kg, fluorogestone acetate, chlormadinone acetate and chlortestasterone acetate 1.0 μg/kg. The recoveries of gestagens spiked in kidney fats at a concentration range of 0.5 to 4 μg/kg were above 86.1% with relative standard deviations (RSD) less than 13.1%. These rapid and reliable methods can be used to efficiently separate, characterize and quantify the residues of gestagens in kidney fats with advantages of shorter time, more sensitive and environmental friendly.
Keywords: Ultra-performance convergence chromatography; Gestagens; Kidney fat; Residues analysis;

A new analytical method has been developed for profiling lipophilic reactive carbonyls (RCs) such as aldehydes and ketones in biological samples using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) with selected reaction monitoring (SRM). The method consists of several phases, including (1) extraction of lipophilic RCs with a chloroform/methanol mixture; (2) derivatization of the extracted RCs with dansyl hydrazine (DH); and (3) SRM detection of the characteristic product ion of the 5-dimethylaminonaphthalene-1-sulfonyl moiety (m/z 236.1). The analytical results were expressed as RC maps, which allowed for the occurrence and levels of different lipophilic RCs to be visualized. We also developed a highly reproducible and accurate method to extract, purify and derivatize RCs in small volumes of biological specimens. This method was applied to the detection of free RCs in mice plasma samples, and resulted in the detection of more than 400 RCs in samples obtained from C57BL/6J mice. Thirty-four of these RCs were identified by comparison with authentic RCs. This method could be used to investigate the levels of RCs in biological and environmental samples, as well as studying the role of lipid peroxidation in oxidative stress related-disorders and discovering new biomarkers for the early diagnosis of these diseases.
Keywords: Reactive carbonyl; Aldehyde; Dansyl hydrazine; LC/ESI-MS/MS; SRM; Lipid peroxidation;

Intranasal delivery is emerging as a promising alternative for oral or intravenous administration of central nervous system (CNS) drugs, such as pramipexole which is widely used for the treatment of Parkinson's disease. To evaluate the effectiveness of intranasal delivery of pramipexole, preclinical pharmacokinetic and tissue distribution studies following intranasal administration need to be investigated. In this paper, we developed and validated a robust and sensitive LC-MS/MS assay without matrix effect for accurate measurements of pramipexole in mouse plasma and tissue samples. Pramipexole and its stable isotope labeled internal standard (d3-pramipexole) were extracted from biological samples by protein precipitation (PPT) coupled with solid phase extraction (SPE) using weak cation exchange SPE cartridges. Matrix effects were studied using post-column infusion and post-extraction addition experiments by direct monitoring of typical phospholipids including glycerophosphocholines (GPChos) and lysoglycerophosphocholines (Lyso-GPChos). Chromatographic separation was achieved on a Welch Ultimate® XB-CN column using isocratic elution with a run time of 3.0 min. The assay was linear in the concentration range of 0.05–100 ng/mL and the intra- and inter-day precision and accuracy met the acceptance criteria. Compared with previous reported assays, the current sample preparation approach exhibited significant reduction of matrix effects due to the dramatically decreased levels of residual matrix components such as GPChos and Lyso-GPChos. This method has been successfully applied to pharmacokinetic and tissue distribution studies of pramipexole in mice following a single intravenous or intranasal dose of 50 μg/kg.
Keywords: LC-MS/MS; Pramipexole; Matrix effect; SPE; Intranasal delivery;

Development of a tandem affinity phosphoproteomic method with motif selectivity and its application in analysis of signal transduction networks by Laura E. Herring; Kyle G. Grant; Kevin Blackburn; Jason M. Haugh; Michael B. Goshe (166-174).
Phosphorylation is an important post-translational modification that is involved in regulating many signaling pathways. Of particular interest are the growth factor mediated Ras and phosphoinositide 3-kinase (PI3K) signaling pathways which, if misregulated, can contribute to the progression of cancer. Phosphoproteomic methods have been developed to study regulation of signaling pathways; however, due to the low stoichiometry of phosphorylation, understanding these pathways is still a challenge. In this study, we have developed a multi-dimensional method incorporating electrostatic repulsion-hydrophilic interaction chromatography (ERLIC) with tandem IMAC/TiO2 enrichment for subsequent phosphopeptide identification by LC/MS/MS. We applied this method to PDGF-stimulated NIH 3T3 cells to provide over 11,000 unique phosphopeptide identifications. Upon motif analysis, IMAC was found to enrich for basophilic kinase substrates while the subsequent TiO2 step enriched for acidophilic kinase substrates, suggesting that both enrichment methods are necessary to capture the full complement of kinase substrates. Biological functions that were over-represented at each PDGF stimulation time point, together with the phosphorylation dynamics of several phosphopeptides containing known kinase phosphorylation sites, illustrate the feasibility of this approach in quantitative phosphoproteomic studies.
Keywords: Phosphopeptide enrichment; Liquid chromatography; Mass spectrometry; Motif analysis; Pathway analysis;

An ultra fast liquid chromatography coupled with tandem mass spectrometry (UFLC-MS/MS) method was developed and validated for simultaneous analysis of multi-class mycotoxins including aflatoxins (AFB1, AFB2, AFG1 and AFG2), ochratoxin A (OTA), fumonisins (FB1 and FB2) and zearalanone (ZEN) in 20 batches of Angelica sinensis samples collected from different markets and stores in China. The eight mycotoxins were extracted and cleaned up by using QuEChERS-based procedure, and then were quantified under the multiple reaction monitoring (MRM) together with positive and negative ionization modes. Focusing on the optimization of extraction and clean-up conditions, as well as UFLC separation and MS/MS parameters of targeted analytes, the developed method expressed good linearity for the eight mycotoxins within their respective linear ranges with correlation coefficients all higher than 0.9974. The limits of detection (LODs) and quantification (LOQs) ranged from 0.005 to 0.125 μg/kg and from 0.0625 to 0.25 μg/kg, respectively. Recoveries for spiked A. sinensis sample at three different levels were all above 78.9% with relative standard deviations (RSDs) below 6.36% for all analytes. Analysis of real samples demonstrated that two visibly moldy A. sinensis samples were detected with AFB1 of 2.07 and 2.92 μg/kg, and AFG1 of 2.84 and 1.53 μg/kg. The proposed quantitative method with significant advantages including simple pretreatment, rapid determination and high sensitivity would be the preferred candidate for the determination and quantification of multi-class mycotoxin contaminants in complex matrixes, which well fulfilled the maximum residue limits (MRLs) from various countries.
Keywords: A. sinensis; Multi-class mycotoxins; QuEChERS; UFLC-MS/MS; MRM;

A molecularly imprinted polymer for the selective solid-phase extraction of dimethomorph from ginseng samples by Xuanwei Xu; Shuang Liang; Xinxin Meng; Min Zhang; Ying Chen; Dan Zhao; Yueru Li (182-186).
A molecularly imprinted polymer (MIP) was synthesized and evaluated to selectively extract dimethomorph from ginseng samples. Dimethomorph molecularly imprinted polymers with template to monomer molar ratios were contrived and developed via precipitation polymerization employing methacrylic acid as functional monomer, ethylene dimethacrylate as cross-linker and butanone:N-heptane (7:3, v:v)as porogen. The LOD (limit of detection) of this method was 0.002 mg kg−1, and the LOQ (limit of quantification) was 0.005 mg kg−1. The different spiked level of ginseng was 0.1 mg kg−1, 1.0 mg kg−1, 5.0 mg kg−1, and the average recovery of dimethomrph was 89.2–91.6%. Under the optimized condition, good linearity was obtained from 0.01 to 5 mg kg−1 (r 2  ≥ 0.9997) with the relative standard deviations of less than 3.20%. This proposed MISPE-GC procedure eliminated the effect of template leakage on quantitative analysis and could be applied to direct determination of dimethomrph in ginseng samples.
Keywords: Molecularly imprinted polymers; Dimethomorph; Precipitation polymerization; Solid-phase extraction; Ginseng samples;

Determination of the antitubercular drug PA-824 in rat plasma, lung and brain tissues by liquid chromatography tandem mass spectrometry: Application to a pharmacokinetic study by Dominika Bratkowska; Adeola Shobo; Sanil Singh; Linda A. Bester; Hendrik G. Kruger; Glenn E.M. Maguire; Thavendran Govender (187-194).
A selective, sensitive and high performance liquid chromatography-tandem mass spectrometry (LC–(ESI)MS/MS) method has been developed and validated for the quantification of the potent antitubercular drug candidate, PA-824, in rat plasma, lung and brain tissues. Sample clean-up involved protein precipitation and solid-phase extraction. Chromatographic separation was performed on YMC Triart C18 column (150 mm × 3.0 mm, 3.0 μm). The method was validated over the concentration range of 75–1500 ng/mL for plasma, 50–1200 ng/g for lungs and 100–1500 ng/g for brain tissue. Evaluation of the pharmacokinetic properties of PA-824 utilized Sprague Dawley rats with a dosage of 20 mg/kg at various time points. The new method was applied successfully for the determination of PA-824 with liquid desorption followed by liquid chromatography with ultra-high resolution quadrupole time-of-flight mass spectrometry in the different biological samples.
Keywords: LC–(ESI)MS/MS; PA-824; Tuberculosis; Rat plasma; Rat tissues; Pharmacokinetics;