Carnitine, A New Precursor in the Formation of the Plant Growth Regulator Mepiquat
Carnitine, A New Precursor in the Formation of the Plant Growth Regulator Mepiquat
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肉碱，植物生长调节剂缩节胺形成的新前体
DOI：
10.1021/acs.jafc.8b01084
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发表时间：
2018
影响因子：
6.1
通讯作者：
庄红
中科院分区：
文献类型：
--
作者：
袁媛;李雪楠;刘黄友;瞿亚婷;张婉彤;余慧琳;张姣姣;庄红
肉毒碱是植物生长调节剂N，N-二甲基哌啶鎓（mepiquat）形成过程中的有效甲基供体，包括哌啶酸的N-甲基化/脱羧反应，或美拉德途径后的甲基转移反应。使用HPLC-MS/MS在由（i）赖氨酸/果糖/肉毒碱、（ii）赖氨酸/葡萄糖/肉毒碱或（iii）哌啶酸（PipAc）/肉毒碱组成的不同二元或三元模型系统中监测甲哌喹和中间体化合物的形成（180-300 °C，长达180分钟）。在290 °C下孵育120 min后，甲哌喹的最高产率为2.4%（PipAc/肉毒碱模型系统）。在230 °C下180分钟后，在果糖和葡萄糖（美拉德）体系中记录到最高产率。全扫描模式用于监测相应中间体（哌啶和N-甲基哌啶，肉毒碱的脱甲基中间体）的形成。甲哌喹形成的新途径表明，这种热诱导化合物的低水平的出现可能在某些选定的烹饪食品中更为普遍。首次在烤牛肉中检出缩节胺，最高达82.5 μg/kg。如先前研究报告所述，预计这些量不会显著增加通过不同食品的总体暴露量。
Carnitine is demonstrated as an effective methyl donor in the formation of the plant growth regulatorN,N-dimethylpiperidinium (mepiquat), encompassing eitherN-methylation/decarboxylation of pipecolic acid, or Maillard pathways followed by transmethylation reactions. The formation of mepiquat and the intermediate compounds was monitored (180–300 °C, up to 180 min) using HPLC-MS/MS in different binary or ternary model systems composed of (i) lysine/fructose/carnitine, (ii) lysine/glucose/carnitine, or (iii) pipecolic acid (PipAc)/carnitine. The highest yield of mepiquat was 2.4% after 120 min incubation at 290 °C (PipAc/carnitine model system). The highest yield was recorded in fructose and glucose (Maillard) systems after 180 min at 230 °C. The full-scan mode was used to monitor the formation of the corresponding intermediates (piperidine andN-methylpiperidine, the demethylated intermediates of carnitine). The new pathways of mepiquat formation indicate that the occurrence of low levels of this thermally induced compound is potentially more widespread in some selected cooked foodstuffs. For the first time, mepiquat was detected in oven-cooked beef, reaching up to 82.5 μg/kg. These amounts are not expected to significantly contribute to the overall exposure via different foodstuffs, as reported in previous studies.