Hernández-Ruiz J, Arnao M B
Department of Plant Physiology, Faculty of Biology, University of Murcia, Murcia, Spain.
J Agric Food Chem. 2008 Nov 26;56(22):10567-73. doi: 10.1021/jf8022063.
In animals, melatonin (N-acetyl-5-methoxytryptamine) has several physiological roles, mostly related with circadian and seasonal rhythms. In 1995, it was detected in a variety of edible plants, and it is known that melatonin from plant foods is absorbed from the gastrointestinal tract and incorporated in the blood stream. This indoleamine also crosses the blood-brain barrier and the placenta, being incorporated at the subcellular level. The possibility of modulating blood melatonin levels in mammals and avians through the ingestion of plant foodstuffs seems to be an interesting prospect. However, data concerning the melatonin content of edible plants are scarce and have not been contrasted. Obtained with very different analytical techniques, in some cases inappropriate, the quantitative data show a high degree of variation. Possibly for the first time in plants, we have used liquid chromatography with time-of-flight/mass spectrometry to identify melatonin. This sophisticated technique, combined with the more commonly used liquid chromatography with fluorescence detection for melatonin quantification, has permitted us to describe the distribution of this compound in different organs and zones in plants. Also, changes in melatonin levels with age and the possible influence of a light/dark photoperiod or constant darkness on its levels are studied. The proposal, applied here to lupin (Lupinus albus L.) and barley (Hordeum vulgare L.), may also serve as a model for application to other plant foodstuffs.
在动物体内，褪黑素（N-乙酰-5-甲氧基色胺）具有多种生理作用，大多与昼夜节律和季节节律相关。1995年，人们在多种可食用植物中检测到了褪黑素，并且已知植物性食物中的褪黑素可从胃肠道吸收并进入血液循环。这种吲哚胺还能穿过血脑屏障和胎盘，并在亚细胞水平上被整合。通过摄入植物性食物来调节哺乳动物和鸟类血液中褪黑素水平的可能性似乎是一个有趣的研究方向。然而，关于可食用植物中褪黑素含量的数据很少，且尚未得到对比。由于采用了非常不同的分析技术，在某些情况下甚至并不合适，因此定量数据显示出高度的变异性。我们可能首次在植物中使用液相色谱-飞行时间/质谱联用技术来鉴定褪黑素。这项先进技术与更常用的用于褪黑素定量的液相色谱-荧光检测相结合，使我们能够描述这种化合物在植物不同器官和部位的分布情况。此外，还研究了褪黑素水平随植物年龄的变化以及光/暗光周期或持续黑暗对其水平的可能影响。这里应用于羽扇豆（白羽扇豆）和大麦的研究方法，也可作为应用于其他植物性食物的模型。
