An LC-MS/MS method for determination of novel fungicide pyraoxystrobin in rat plasma and tissues: Toxicokinetics and tissue distribution study.

A simple, specific and reproducible liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of pyraoxystrobin in rat plasma and tissues. Chromatographic separation was achieved on a Zorbax Extend-C18 column (50×2.1mm I. D., 3.5µm), using a gradient mobile phase consisting of acetonitrile and 0.1% aqueous formic acid (v/v) at a flow rate of 0.5mL min(-1). Pyraoxystrobin and picoxystrobin (internal standard) were detected without interference in the selected reaction monitoring (SRM) mode with positive electrospray ionization. Further, the method was validated following FDA guideline. The calibration curves for plasma and tissues were linear over a concentration range of 1.00-200ng mL(-1), with lower limits of quantitation of 1.00ng mL(-1). Mean extraction recoveries in plasma and tissues ranged from 101.4% to 108.2% and from 49.1% to 59.4%, respectively. The intra-day and inter-day precision in plasma and tissues were within 9.9% and 8.9%, and the intra-day and inter-day accuracy ranged from 88.7% to 110.7% and 93.2% to 108.7%, respectively. Finally, the validated method was successfully applied to toxicokinetics and tissue distribution studies after oral administration of pyraoxystrobin to rats.

Inhibitory mechanisms of resveratrol in platelet activation: pivotal roles of p38 MAPK and NO/cyclic GMP.

Resveratrol has been reported to have antiplatelet activity; however, the detailed mechanisms have not yet been resolved. This study aimed to systematically examine the detailed mechanisms of resveratrol in the prevention of platelet activation in vitro and in vivo. Resveratrol (0.05-0.25 micromol/l) showed stronger inhibition of platelet aggregation stimulated by collagen (1 microg/ml) than other agonists. Resveratrol (0.15 and 0.25 micromol/l) inhibited collagen-induced platelet activation accompanied by [Ca(+2)]i mobilization, thromboxane A(2) (TxA(2)) formation, phosphoinositide breakdown, and protein kinase C (PKC) activation. Resveratrol markedly increased levels of NO/cyclic guanosine monophosphate (GMP), and cyclic GMP-induced vasodilator-stimulated phosphoprotein phosphorylation. Resveratrol markedly inhibited p38 mitogen-activated protein kinase (MAPK) but not Jun N-terminal kinase or extracellular signal-regulated kinase-2 phosphorylation in washed platelets. Resveratrol-reduced hydroxyl radical (OH(-)) formation in the electron spin resonance study. In an in vivo study, resveratrol (5 mg/kg) significantly prolonged platelet plug formation of mice. In conclusion, the main findings of this study suggest that the inhibitory effects of resveratrol possibly involve (i) inhibition of the p38 MAPK-cytosolic phospholipase A(2)-arachidonic acid-TxA(2)-[Ca(+2)]i cascade and (ii) activation of NO/cyclic GMP, resulting in inhibition of phospholipase C and/or PKC activation. Resveratrol is likely to exert significant protective effects in thromboembolic-related disorders by inhibiting platelet aggregation.