This study aimed to develop a rapid, sensitive, and specific LC–tandem mass spectrometry method for the determination of nootkatone in rat plasma. α-Cyperone was chosen as the internal standard (IS). The plasma was processed using a one-step acetonitrile protein precipitation method. Chromatographic separation of nootkatone was achieved on a Phenomenex Kinetex XB-C18 column (2.10 × 50 mm, 2.6 μm) at 35°C with a mobile phase consisting of acetonitrile and water under a gradient elution at a flow rate of 0.35 mL/min. An electrospray ionization source was applied and operated in positive ion and multiple reaction monitoring modes. Nootkatone and IS were quantified using the transitions of m/z 219.200 → 163.110 and m/z 219.200 → 111.000, respectively. The calibration curves were linear over the range of 10–2000 ng/mL (r = 0.9943). The lower limit of quantification was 10 ng/mL. The intra- and inter-day precision (relative standard deviation) ranged from 2.56% to 8.41%, with the accuracy values ranging from 98.9% to 99.17% for four different concentration levels. The matrix effect and extraction recovery were within acceptable limits. The validated method was successfully applied to the pharmacokinetic study of nootkatone in rats after oral and intravenous administration at three dosages. The main pharmacokinetic parameters were calculated, showing low bioavailability of nootkatone.

中文翻译：

---

LC-串联质谱法测定大鼠血浆中诺卡酮及其在药代动力学研究中的应用

本研究旨在开发一种快速、灵敏、特异的 LC-串联质谱法，用于测定大鼠血浆中的诺卡酮。选择 α-Cyperone 作为内标 (IS)。使用一步乙腈蛋白质沉淀法处理血浆。nootkatone 的色谱分离是在 Phenomenex Kinetex XB-C18 色谱柱 (2.10 × 50 mm, 2.6 μm) 上在 35°C 下实现的，流动相由乙腈和水组成，梯度洗脱，流速为 0.35 mL/min。应用电喷雾离子源，并在正离子和多反应监测模式下运行。Nootkatone 和 IS 使用m/z 219.200 → 163.110 和m/z的离子对进行量化分别为 219.200 → 111.000。校准曲线在 10–2000 ng/mL 范围内呈线性 ( r  = 0.9943)。定量下限为 10 ng/mL。日内和日间精度（相对标准偏差）范围为 2.56% 至 8.41%，四种不同浓度水平的准确度值范围为 98.9% 至 99.17%。基质效应和萃取回收率在可接受的范围内。经验证的方法成功应用于大鼠口服和静脉给药三种剂量诺卡酮的药代动力学研究。计算了主要的药代动力学参数，显示诺卡酮的生物利用度低。