Development of an online solid-phase extraction-liquid chromatography-mass spectrometric analysis of oxcarbazepine and its active metabolite licarbazepine from plasma with a direct injection step.

We developed an online solid phase extraction procedure using a hydrophilic-lipophilic balance sorbent, with reversed-phase liquid chromatography-high-resolution mass spectroscopy for the determination of oxcarbazepine and its active metabolite licarbazepine in plasma samples. The analytes were detected using a high-resolution Q Orbitrap mass spectrometer with targeted-selected ion monitoring (t-SIM) in positive scan mode. Under the optimized conditions, the method was linear with R2 values >0.99. The method was linear from 0.008 to 2.000 µg mL-1 and the lower limit of quantification was 0.008 µg mL-1 for both oxcarbazepine and licarbazepine. Recoveries ranged from 92.34 to 104.27% and from matrix-matched samples from 94.26 to 104.19%. The intraday and interday precision RSD values were <9.13% with an associated accuracy of 92.71 to 104.06%. The total time for the one step online procedure was only 8 min. This method provides a direct and accurate measurement for therapeutic drug monitoring of oxcarbazepine and its active metabolite licarbazepine.

Liquid chromatography separation of the chiral prodrug eslicarbazepine acetate and its main metabolites in polar organic mode. Application to their analysis after in vitro metabolism.

A LC method using a chiral stationary phase (CSP) with cellulose tris(3-chloro-4-methylphenylcarbamate) as chiral selector in polar organic mode (POM) was developed for the separation of the biopharmaceutic classification system (BCS) class II chiral prodrug eslicarbazepine acetate (ESL) and its main metabolites, namely eslicarbazepine, its optical antipode, (R)-licarbazepine, and the achiral oxcarbazepine (OXC). The percentage of methanol (MeOH) in the mobile phase containing acetonitrile (ACN) as the main solvent was found to significantly influence analyte retention and resolution. A reversal of elution order of OXC and (R)-licarbazepine was observed, depending on the MeOH percentage in the mobile phase. The optimized mobile phase consisted of ACN/MeOH/acetic acid/diethylamine (95/5/0.2/0.07; v/v/v/v). The potential of this chemo- and enantioselective LC method combined with solid-phase extraction (SPE) was then evaluated for in vitro metabolism studies using ESL as a model case. Only eslicarbazepine could be detected after incubation of ESL in human liver microsome systems.

Development and validation of an enantioselective liquid-chromatography/tandem mass spectrometry method for the separation and quantification of eslicarbazepine acetate, eslicarbazepine, R-licarbazepine and oxcarbazepine in human plasma.

The purpose of this study was develop and validate a sensitive and specific enantioselective liquid-chromatography/tandem mass spectrometry (LC-MS/MS) method, for the simultaneous quantification of eslicarbazepine acetate (ESL), eslicarbazepine (S-Lic), oxcarbazepine (OXC) and R-licarbazepine (R-Lic) in human plasma. Analytes were extracted from human plasma using solid phase extraction and the chromatographic separation was achieved using a mobile phase of 80% n-hexane and 20% ethanol/isopropyl alcohol (66.7/33.3, v/v). A Daicel CHIRALCEL OD-H column (5 µm, 50 mm × 4.6 mm) was used with a flow rate of 0.8 mL/min, and a run time of 8 min. ESL, S-Lic, R-Lic, OXC and the internal standard, 10,11-dihydrocarbamazepine, were quantified by positive ion electrospray ionization mass spectrometry. The method was fully validated, demonstrating acceptable accuracy, precision, linearity, and specificity in accordance with FDA regulations for the validation of bioanalytical methods. Linearity was proven over the range of 50.0-1000.0 ng/mL for ESL and OXC and over the range of 50.0-25,000.0 ng/mL for S-Lic and R-Lic. The intra- and inter-day coefficient of variation in plasma was less than 9.7% for ESL, 6.0% for OXC, 7.7% for S-Lic and less than 12.6% for R-Lic. The accuracy was between 98.7% and 107.2% for all the compounds quantified. The lower limit of quantification (LLOQ) was 50.0ng/mL for ESL, S-Lic, OXC and R-Lic in human plasma. The short-term stability in plasma, freeze-thaw stability in plasma, frozen long-term stability in plasma, autosampler stability and stock solution stability all met acceptance criteria. The human plasma samples, collected from 8 volunteers, showed that this method can be used for therapeutic monitoring of ESL and its metabolites in humans treated with ESL.

Four new fluorenone alkaloids and one new dihydroazafluoranthene alkaloid from Caulophyllum robustum Maxim.

Four new fluorenone alkaloids, caulophylline A-D (1-4), and one new dihydroazafluoranthene alkaloid, caulophylline E (5) were isolated from the roots of Caulophyllum robustum Maxim. Their structures were elucidated by spectroscopic analysis. Among the isolated alkaloids, Caulophylline E showed good scavenging effects against DPPH radical with IC(50) of 39 µM.

Optimizing the extraction, separation and quantification of tricyclic antidepressant drugs in human plasma with CE-ESI-TOF-MS using cationic-coated capillaries.

In this study, the extraction and CE-ESI-TOF-MS analysis of tricyclic antidepressant (TCA) drugs imipramine, desipramine, clomipramine and norclomipramine in human plasma has been optimized. The CE capillaries were modified with ω-iodo-alkyl ammonium salt (M7C4I coating) to reduce analyte adsorption to the silica wall. The use of a strong cation exchange (SCX) solid-phase extraction (SPE) column specifically designed for the extraction of basic drug species from biofluids gave very clean extracts with high and reproducible recoveries. The extraction recoveries were ranging between 87 and 91% with % RSD values of 0.5-1.7% (n=3). The obtained strong cation exchange-SPE extracts of the TCA in human plasma only contained the analytes of interest. The optimized CE separation conditions were obtained by adding ACN and acetic acid to the sample while using an aqueous BGE. The CE-ESI-TOF-MS analysis was performed within 6 min for all TCA analytes under the optimized condition with peak efficiencies up to 1.4 x 105 plates/m and an average % RSD of the migration times of the analytes of 0.3% (n=5). The presented method can readily be used for the extraction and quantification of basic drug species in human biological fluids and in pharmaceutical formulations.

Evaluating indole-related derivatives as precursors in the directed biosynthesis of diazepinomicin analogues.

The effectiveness of precursor-directed biosynthesis to generate diazepinomicin (1) analogues with varied ring-A substitutents was investigated by feeding commercially available, potential ring-A precursors such as fluorinated tryptophans, halogenated anthranilates, and various substituted indoles into growing actinomycete culture DPJ15 (genus Micromonospora). Two new monofluorinated diazepinomicin analogues (2 and 3) were identified and characterized by spectroscopic methods. Both derivatives showed modest antibacterial activity against the Gram-positive coccus Staphylococcus aureus with MIC values in the range 8-32 microg/mL.

Diazepinomicin, a new antimicrobial alkaloid from a marine Micromonospora sp.

The structure of a new dibenzodiazepine alkaloid, diazepinomicin (1), isolated from the culture of a marine actinomycete of the genus Micromonospora was characterized using spectroscopic methods. Diazepinomicin represents a unique molecular class composed of a dibenzodiazepine core linked to a farnesyl side chain.

Separation of tricyclic psychosedative drugs by high-speed ion-pair partition and liquid-solid adsorption chromatography.

The application of high-speed ion-pair partition and liquid-solid adsorption chromatography to the separation of twenty common tricyclic tranquilizers and antidepressant drugs is described. In the ion-pair system, amine-perchlorate ion-pairs were extracted from an aqueous stationary phase supported on 10-mum silica gel by organic eluents containing a chloromethane and a higher aliphatic alcohol, and chromatographic parameters for elution by eight eluent mixtures are presented. Using 5 mm times 120 mm columns good separations, according to chemical class, were achieved. For adsorption chromatography, the components were eluted from 20-mum spherical alumina using eluents containing methylene chloride, n-hexane or n-pentane, and acetic acid. Chromatographic parameters are given for eight eluent compositions. Components differing little in structure are well separated by liquid-solid adsorption chromatography. Compared with ion-pair partition chromatography, adsorption chromatography is much more selective for compounds of the same chemical type. The two methods are therefore complementary. Both methods gave plate heights in the range of 0.1 to 0.3 mm.