Analytical tools for elucidating the biological role of melatonin in plants by LC‐MS/MS

Abstract

Melatonin (MT) presence in higher plants was recently discovered and the knowledge of its function in vivo is limited. Several studies have recently shown the occurrence of MT and related compounds in grapes and wines. The analysis of MT in plants and foods represents a highly challenging task due to its wide concentration range, the difficulty in the selection of the extraction solvents because of its amphipathic nature, and the fact that it reacts quickly with other matrix components. Thus, sample processing factors; preparation/cleanup procedures; and chromatographic/detection parameters, such as HILIC and reverse phase (C(8) and C(18)) chromatographic modes, ESI, and atmospheric pressure chemical ionization (APCI) in both negative and positive modes were evaluated. Taken together, we have demonstrated that optimal conditions were quite different for each of the matrices under study. A sonication-mediated extraction step was necessary for grape skin (100% v/v methanol) and plant tissues (50% v/v methanol), while wine and must required a SPE preconcentration step. HILIC-(+) APCI ionization was better for MT standards, while C(8) -(+) APCI was the best choice for grape skin and C(18) -(+ESI) was suitable for wine. On the other hand, C(8) -(+)ESI was the most appropriate for vegetal tissues of Arabidopsis thaliana. Proposed methods were validated and the LODs were in the low picogram levels range. The optimized approaches were applied to the determination of MT and its isomer in different vegetal/food samples; levels found within the range: 4.9-440 ng/g.

Solid phase extraction/cyclodextrin-modified micellar electrokinetic chromatography for the analysis of melatonin and related indole compounds in plants

“…4 shows an electropherogram of the assayed samples. The obtained values are shown in Table 4 and are in agreement with previous works [23,[39][40][41]. Indole compounds were detected and quantified, indicating the valuable potential application of the present method for food and vegetal analysis.…”

“…In this case, different detectors such as fluorescence (FI) [14][15][16][17], electrochemical (ECD) [18,19], and UV [20][21][22] have been used. With the development of MS interface technology, high performance liquid chromatography coupled to mass spectrometry (HPLC-MS) has increased in popularity and has proved to be a powerful tool for complex sample analysis [2,3,[23][24][25].…”

MALDI-MSI: a fast and reliable method for direct melatonin quantification in biological fluids

“…Although this is a usual approach, a thorough method validation was necessary to be performed. The obtained data not only have presented satisfactory results in all the analyzed parameters but have also indicated that MALDI-MSI is a sensitive methodology, with lower limit of detection when compared to classical techniques, such as LC-MS/MS and RIA (Rowe and Kennaway 2002;Gomez et al 2013;Voultsios et al 1997). …”

Screen-printed electrodes modified with carbon nanotubes or graphene for simultaneous determination of melatonin and serotonin

“…Since then, it has been found in more than 140 different plant species and foods [5][6][7][8][9][10][11][12][13]. Furthermore, healthy subjects synthesize melatonin not only in the pineal gland [14], but also in a wide range of other organs.…”