This research proposed and validated an LC-MSMS method for five reduction and hydroxylation metabolites of Mequindox (MEQ) as well as the precursor in holothurian samples. Specially, three hydroxylation metabolites (2-isoethanol-mequindox, M3, 2-isoethanol-1-desoxymequindox, M4 and 2-isoethanol-4-desoxymequindox, M5) are novel for analysis. Target compounds were extracted with methanol and ethyl acetate in turn without any complicated acidolysis, alkaline hydrolysis or enzymolysis steps. Samples were further purified with C18 solid-phase extraction cartridges for LC-MSMS analysis. Mean recoveries in spiked samples ranged from 81 to 107% with intra-day relative standard deviation (RSD) and inter-day RSD <11.2 and 9.9%, respectively. Limit of detection was determined based on signal-to-noise ratio ≥3 ranged from 0.16 to 2.11 μg kg−1 for each target. The validated protocol was successfully applied for commercial holothurian samples with a positive rate at 13.3%. And concentrations of hydroxylation metabolites were higher than reduction metabolites and precursor MEQ in positive samples.

中文翻译：

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通过超高效液相色谱-串联质谱法分析海参中毒喹乙醇的还原和羟基化代谢物

本研究提出并验证了一种 LC-MSMS 方法，用于测定海参样品中的五种甲基喹乙醇 (MEQ) 及其前体的还原和羟基化代谢物。特别地，三种羟基化代谢物（2-isoethanol-mequindox，M3，2-isoethanol-1-desoxymequindox，M4 和 2-isoethanol-4-desoxymequindox，M5）是新的分析。目标化合物依次用甲醇和乙酸乙酯萃取，没有任何复杂的酸解、碱解或酶解步骤。用 C18 固相萃取柱进一步纯化样品，用于 LC-MSMS 分析。加标样品的平均回收率为 81% 至 107%，日内相对标准偏差 (RSD) 和日间 RSD 分别小于 11.2 和 9.9%。检测限是根据信噪比 ≥ 3 确定的，范围从 0.16 到 2。每个目标 11 μg kg−1。经过验证的协议成功应用于商业海参样品，阳性率为 13.3%。并且羟基化代谢物的浓度高于阳性样品中的还原代谢物和前体MEQ。