A sensitive, fast and robust liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of usaramine (USM) and usaramine N-oxide (UNO) in rat plasma. The separation was conducted on an ACQUITY UPLC BEH C18 Column (50 × 2.1 mm, 1.7 μm), and gradient eluted with mobile phase A (0.1% formic acid with 5 mM ammonium acetate in water) and B (0.1% formic acid in acetonitrile/methanol, 9/1, v/v). The method was linear over the range of 1–2000 ng/mL for both analytes. The validated method was applied to investigate the pharmacokinetic behaviors and sex differences of USM and its N-oxide metabolite in rats. After intravenous administration of USM at 1 mg/kg, the AUC0-t values for USM and UNO were 363 ± 65 and 172 ± 32 ng/mL*h in male rats, respectively, while 744 ± 122 and 30.7 ± 7.4 ng/mL*h in females, respectively. The clearance of USM was significantly higher in male rats than in females (2.77 ± 0.50 vs 1.35 ± 0.19 L/h/kg, p < 0.05). After oral administration of USM at 10 mg/kg, the AUC0-t values of USM and UNO were 1960 ± 208 and 1637 ± 246 ng/mL*h in male rats, respectively, while 6073 ± 488 and 300 ± 62 ng/mL*h in females, respectively. The oral bioavailability of USM in female rats (81.7%) was much higher than in males (54.0%). In conclusion, sex-based differences were observed in the pharmacokinetics, N-oxide metabolism and oral bioavailability of USM.

中文翻译：

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使用液相色谱-串联质谱法定量大鼠血浆中的乌沙拉胺及其 N-氧化物代谢物

开发并验证了一种灵敏、快速和稳健的液相色谱串联质谱 (LC-MS/MS) 方法，用于测定大鼠血浆中的乌沙拉碱 (USM) 和乌沙拉碱 N-氧化物 (UNO)。在 ACQUITY UPLC BEH C18 色谱柱（50 × 2.1 mm，1.7 μm）上进行分离，并用流动相 A（0.1% 甲酸，含 5 mM 乙酸铵的水溶液）和 B（0.1% 甲酸的乙腈溶液）进行梯度洗脱/甲醇，9/1，v/v)。对于两种分析物，该方法在 1–2000 ng/mL 范围内呈线性。应用经验证的方法研究USM及其N-氧化物代谢物在大鼠体内的药代动力学行为和性别差异。USM 1 mg/kg 静脉给药后，雄性大鼠 USM 和 UNO 的 AUC0-t 值分别为 363 ± 65 和 172 ± 32 ng/mL*h，而雄性大鼠分别为 744 ± 122 和 30.7 ± 7.4 ng/mL *h 在女性中，分别。雄性大鼠中 USM 的清除率显着高于雌性（2.77 ± 0.50 vs 1.35 ± 0.19 L/h/kg，p < 0.05）。雄性大鼠口服 USM 10 mg/kg 后，USM 和 UNO 的 AUC0-t 值分别为 1960 ± 208 和 1637 ± 246 ng/mL*h，而 USM 和 UNO 的 AUC0-t 值分别为 6073 ± 488 和 300 ± 62 ng/mL *h 在女性中，分别。USM在雌性大鼠中的口服生物利用度（81.7%）远高于雄性大鼠（54.0%）。总之，在 USM 的药代动力学、N-氧化物代谢和口服生物利用度方面观察到基于性别的差异。分别为 6073 ± 488 和 300 ± 62 ng/mL*h，女性分别为。USM在雌性大鼠中的口服生物利用度（81.7%）远高于雄性大鼠（54.0%）。总之，在 USM 的药代动力学、N-氧化物代谢和口服生物利用度方面观察到基于性别的差异。分别为 6073 ± 488 和 300 ± 62 ng/mL*h，女性分别为。USM在雌性大鼠中的口服生物利用度（81.7%）远高于雄性大鼠（54.0%）。总之，在 USM 的药代动力学、N-氧化物代谢和口服生物利用度方面观察到基于性别的差异。