1. A sensitive liquid chromatographic-tandem mas spectrometric assay was developed and validated to determine the major metabolite of betahistine, 2-pyridylacetic acid, in human plasma. 2. The analyte was extracted from plasma samples by liquid-liquid extraction and analysed using liquid chromatography-tandem mass spectrometry with an electrospray ionization interface. The method has a lower limit of quantitation of 1 ng ml(-1) fir a 0.5-ml plasma aliquot. The intra- and interday precision (relative standard deviation), calculated from quality control (QC) samples, was less than 10%. Accuracy as determined from QC samples was within +/-7%. 3. The validated method was successfully applied to a pharmacokinetic study of betahistine in healthy volunteers. After oral administration of a single dose of 24 mg betahistine mesylate to 20 healthy Chinese male volunteers, Cmax was 339.4 ng ml(-1) (range 77.3-776.4 ng ml(-1)). The t(1/2) was 5.2 h (range 2.0(-1)-11.4h). The AUC(0-t) obtained was 1153.5 ng ml(-1) h (range 278.5-3150.8 ng ml(-1)). The disposition of the metabolite exhibited a marked interindividual variation. 4. The plasma concentrations of the parent drug were less than 0.5 ng ml(-1), suggesting that it undergoes almost complete first-pass metabolism. The reported two active metabolites were not detected in the plasma of any volunteer. Although there is no evidence that the major metabolite has pharmacological activity, the clinical importance of 2-pyridylacetic acid in humans should be reinvestigated.

1. A sensitive liquid chromatographic-tandem mas spectrometric assay was developed and validated to determine the major metabolite of betahistine, 2-pyridylacetic acid, in human plasma. 2. The analyte was extracted from plasma samples by liquid-liquid extraction and analysed using liquid chromatography-tandem mass spectrometry with an electrospray ionization interface. The method has a lower limit of quantitation of 1 ng ml(-1) fir a 0.5-ml plasma aliquot. The intra- and interday precision (relative standard deviation), calculated from quality control (QC) samples, was less than 10%. Accuracy as determined from QC samples was within +/-7%. 3. The validated method was successfully applied to a pharmacokinetic study of betahistine in healthy volunteers. After oral administration of a single dose of 24 mg betahistine mesylate to 20 healthy Chinese male volunteers, Cmax was 339.4 ng ml(-1) (range 77.3-776.4 ng ml(-1)). The t(1/2) was 5.2 h (range 2.0(-1)-11.4h). The AUC(0-t) obtained was 1153.5 ng ml(-1) h (range 278.5-3150.8 ng ml(-1)). The disposition of the metabolite exhibited a marked interindividual variation. 4. The plasma concentrations of the parent drug were less than 0.5 ng ml(-1), suggesting that it undergoes almost complete first-pass metabolism. The reported two active metabolites were not detected in the plasma of any volunteer. Although there is no evidence that the major metabolite has pharmacological activity, the clinical importance of 2-pyridylacetic acid in humans should be reinvestigated.

Toxoplasma gondii (T. gondii) is an important health problem in human and animals, and the highlighting side effects of launched therapeutic chemicals cannot be ignored. Thus, it is urgent to develop new drugs to against the infection. Myrislignan originated from nutmeg exhibited excellent anti-T. gondii activity in vitro and in vivo, and was able to destroy mitochondrial function. However, the exact mechanism of action is still unknown. In this study, combining RNAs deep-sequencing analysis and surface plasmon resonance (SPR) analysis, the differentially expressed genes (DEGs) and high affinity proteins suggested that myrislignan may affect the oxidation-reduction process of T. gondii. Furthermore, the upregulating ROS activity after myrislignan incubation verified that myrislignan destroyed the oxidant-antioxidant homeostasis of tachyzoites. Transmission electron microscopy (TEM) indicated that myrislignan induced the formation of autophagosome-like double-membrane structure. Moreover, monodansyl cadaverine (MDC) staining and western blot further illustrated autophagosome formation. Myrislignan treatment induced a significant reduction in T. gondii by flow cytometry analysis. Together, these findings demonstrated that myrislignan can induce the oxidation-reduction in T. gondii, lead to the autophagy, and cause the death of T. gondii.

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Background Myrislignan is a natural product from Myristica sp. with diverse pharmacological activities. Recently, the anti-Toxoplasma gondii (T. gondii) activity of myrislignan has been proposed, and in vivo studies of its pharmacokinetics in BALB/c mice are necessary to further evaluate the clinical effects of myrislignan. Results In this study, a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to quantify myrislignan levels in mouse plasma using dehydrodiisoeugenol as an internal standard (IS) in positive ion mode. Chromatographic separation of the analytes was achieved using an ACE Ultracore Super C18 analytical column (2.5 μm, 2.1 × 50 mm) at 30 °C. A gradient mobile phase consisting of water (0.1 % formic acid) and acetonitrile (0.1 % formic acid) was delivered at a flow rate of 0.4 mL/min. Myrislignan and the IS eluted at 1.42 and 1.71 min, respectively. A good excellent linear response across the concentration range of 1-1000 ng/mL was achieved (r2 = 0.9973). The lower limit of quantification (LLOQ) was 1 ng/mL, and the inter- and intra-day accuracy and precision of the method showed relative standard deviations (RSDs) less than 10 %. The method was applied to examine the pharmacokinetics of myrislignan in mouse plasma following a single oral administration of 200 mg/kg or intraperitoneal administration of 50 mg/kg myrislignan, and the bioavailability (F) of orally administered myrislignan was only 1.97 % of the bioavailability of intraperitoneally administered myrislignan. Conclusions A rapid and sensitive LC-MS/MS method has been was developed, validated and successfully used to determine myrislignan levels in mice after oral or intraperitoneal administration. This study is the first to report the pharmacokinetic parameters of myrislignan in mice and to compare its pharmacokinetics after oral and intraperitoneal administration, which will be useful for further research on the administration of myrislignan in animals and humans.