Simultaneous quantification of atractyloside and carboxyatractyloside in rat plasma by LC-MS/MS: Application to a pharmacokinetic study after oral administration of Xanthii Fructus extract.

Xanthii Fructus is extensively used as an herbal medicine. Ingestion of this herb is associated with severe hepatotoxicity and nephrotoxicity. Atractyloside and carboxyatractyloside are two dominative toxic constituents in Xanthii Fructus. However, their pharmacokinetic study is lacking. In this study, a novel high-performance liquid chromatography-tandem mass spectrometry method was developed to simultaneously quantify the rat plasma concentrations of atractyloside and carboxyatractyloside. After protein precipitation, the analytes were chromatographic separated on a ZORBAX Eclipse Plus column (2.1 × 150 mm id, 5 µm) under gradient elute. In the negative electrospray ionization mode, the transitions at m/z 725.3→645.4 for atractyloside, m/z 769.3→689.4 for carboxyatractyloside, and m/z 479.2→121.1 for paeoniflorin (the internal standard) were acquired by multiple reaction monitoring. This analytical method showed good linearity over 1-500 ng/mL for atractyloside and 2-500 ng/mL for carboxyatractyloside with acceptable precision and accuracy. No matrix effect, instability and carryover occurred in the analysis procedure. The extraction recoveries were greater than 85.0%. This method was applied to a preliminary pharmacokinetic study by orally administering Xanthii Fructus extract (9 g/kg) to rats, which was useful to evaluate the role of these two compounds in Xanthii Fructus-induced toxicity.

Postconditioning for salvage of ischemic skeletal muscle from reperfusion injury: efficacy and mechanism.

We tested our hypothesis that postischemic conditioning (PostC) is effective in salvage of ischemic skeletal muscle from reperfusion injury and the mechanism involves inhibition of opening of the mitochondrial permeability transition pore (mPTP). In bilateral 8x13 cm pig latissimus dorsi muscle flaps subjected to 4 h ischemia, muscle infarction increased from 22+/-4 to 41+/-1% between 2 and 24 h reperfusion and remained unchanged at 48 (38+/-6%) and 72 (40+/-1%) h reperfusion (P<0.05; n=4 pigs). PostC induced by four cycles of 30-s reperfusion/reocclusion at the onset of reperfusion after 4 h ischemia reduced muscle infarction from 44+/-2 to 22+/-2% at 48 h reperfusion. This infarct protective effect of PostC was mimicked by intravenous injection of the mPTP opening inhibitor cyclosporin A or NIM-811 (10 mg/kg) at 5 min before the end of 4 h ischemia and was abolished by intravenous injection of the mPTP opener atractyloside (10 mg/kg) at 5 min before PostC (P<0.05; n=4-5 pigs). PostC or intravenous cyclosporin A injection at 5 min before reperfusion caused a decrease in muscle myeloperoxidase activity and mitochondrial free Ca2+ concentration and an increase in muscle ATP content after 4 h ischemia and 2 h reperfusion compared with the time-matched controls. These effects of PostC were abolished by intravenous injection of atractyloside at 5 min before PostC (P<0.05; n=6 pigs). These observations support our hypothesis that PostC is effective in salvage of ischemic skeletal muscle from reperfusion injury and the mechanism involves inhibition of opening of the mPTP.