Validated Liquid–Liquid Extraction and LC–ESI–MS Method for the Determination of Melitracen in Human Plasma

Melitracen and the internal standard (I.S.), trifluoperazine, were extracted from plasma by a convenient liquid-liquid extraction. Chromatographic separation was performed on a Thermo Hypersil-Hypurity C₁₈ with the mobile phase consisting of 10 mM ammonium acetate–methanol–acetonitrile. A single-quadrupole mass spectrometer with an electrospray interface was operated in the selected-ion monitoring mode to detect the [M + H]⁺ ions at 292 m/z for melitracen and 408 m/z for trifluoperazine. The method was validated over 0.4–50.0 ng mL^?1 for melitracen. The recovery was 73.52–78.91%, and the lower limit of quantitation (LLOQ) detection was 0.4 ng mL^?1 for melitracen. The intra- and inter-day precision of the method at three concentrations were 2.96–7.76% with accuracy of 95.75–100.48%. Stability of compounds was established in a battery of stability studies. The bioequivalence of melitracen in the two formulations was evaluated in 18 healthy Chinese male volunteers with this assay. The described method showed acceptable precision, accuracy, linearity, stability, specificity and can be widely used for pharmacokinetic studies, and routine therapeutic drug monitoring.     

Validated Liquid–Liquid Extraction and LC–ESI–MS Method for the Determination of Melitracen in Human Plasma

Melitracen and the internal standard (I.S.), trifluoperazine, were extracted from plasma by a convenient liquid-liquid extraction. Chromatographic separation was performed on a Thermo Hypersil-Hypurity C₁₈ with the mobile phase consisting of 10 mM ammonium acetate–methanol–acetonitrile. A single-quadrupole mass spectrometer with an electrospray interface was operated in the selected-ion monitoring mode to detect the [M + H]⁺ ions at 292 m/z for melitracen and 408 m/z for trifluoperazine. The method was validated over 0.4–50.0 ng mL⁻¹ for melitracen. The recovery was 73.52–78.91%, and the lower limit of quantitation (LLOQ) detection was 0.4 ng mL⁻¹ for melitracen. The intra- and inter-day precision of the method at three concentrations were 2.96–7.76% with accuracy of 95.75–100.48%. Stability of compounds was established in a battery of stability studies. The bioequivalence of melitracen in the two formulations was evaluated in 18 healthy Chinese male volunteers with this assay. The described method showed acceptable precision, accuracy, linearity, stability, specificity and can be widely used for pharmacokinetic studies, and routine therapeutic drug monitoring.

     

Determination of (E)-3,5,4′-Trimethoxystilbene in Rat Plasma by LC with ESI-MS

(E)-3,5,4′-trimethoxystilbene (BTM-0512) is a resveratrol analog with a variety of pharmacological action, including anti-cancer properties, anti-allergic activity, estrogenic activity, antiangiogenic activity, and vascular-targeting activity against microtubule-destabilization. There is, however, no validated analytical method for quantification of (E)-3,5,4′-trimethoxystilbene in biological matrices, so pharmacokinetic data and suitable methods for determination of the compound in plasma are currently lacking. A rapid and sensitive liquid chromatographic–mass spectrometric method for determination of (E)-3,5,4′-trimethoxystilbene in rat plasma, using carbamazepine as internal standard, has been developed and validated. Plasma samples were treated with acetonitrile to precipitate proteins. Samples were then analyzed by HPLC on a 250mm × 4.6 mm i.d., 5-μm particle, C₁₈ column with methanol–water, 80:20 (v/v), containing 10 mm ammonium acetate and 0.2% formic acid (pH 3.0), as mobile phase, delivered at 0.85 mL min⁻¹. A single-quadrupole mass spectrometer with an electrospray interface operated in selected-ion monitoring mode was used to detect [M + H]⁺ ions at m/z 271.3 for (E)-3,5,4′-trimethoxystilbene and m/z 237.5 for the internal standard. (E)-3,5,4′-trimethoxystilbene and the internal standard eluted as sharp, symmetrical peaks with retention times of 8.9 and 4 min, respectively. Calibration plots for (E)-3,5,4′-trimethoxystilbene in rat plasma at concentrations ranging from 0.01 to 5.0 μg mL⁻¹ were highly linear. Intra-day and inter-day precision, as RSD, was <12.9%, and accuracy was in the range 94.8–104.7%. The limit of detection in plasma was 0.005 μg mL⁻¹. The method was successfully used to determine the concentration of (E)-3,5,4′-trimethoxystilbene after oral administration of 86 mg kg⁻¹ of the drug to Sprague–Dawley rats and can be used to investigate the pharmacokinetics of the compound.     

LC–ESI–MS Determination of Flupentixol in Human Plasma

Flupentixol and an internal standard, loperamide were extracted from human plasma by liquid–liquid extraction and analyzed on a Thermo Hypersil HyPURITY C18 column, with 10 mM ammonium acetate–acetonitrile–methanol (26:62:12, v/v/v) as mobile phase, coupled with electrospray ionization mass spectrometry (ESI–MS). The protonated analyte was quantified by selected-ion monitoring (SIM) with a quadrupole mass spectrometer in a positive-ion mode. The calibration curve was linear (r = 0.9990) over the concentration range: 0.039–2.5 ng mL^?1. Intra-day and inter-day precision (RSD%) were less than 13.05%. The established method was successfully applied for the determination of pharmacokinetics of flupentixol in human plasma.