Determination of melatonin in wine and plant extracts by capillary electrochromatography with immobilized carboxylic multi‐walled carbon nanotubes as stationary phase

Abstract

The finding of melatonin, the often called "hormone of darkness" in plants opens an interesting perspective associated to the plethora of health benefits related to the moderate consumption of red wine. In this study, the implementation of a new method for the determination of melatonin in complex food matrices by CEC with immobilized carboxylic multi-walled carbon nanotubes as stationary phase is demonstrated. The results indicated high electrochromatographic resolution, good capillary efficiencies and improved sensitivity respect to those obtained with conventional capillaries. In addition, it was demonstrated highly reproducible results between runs, days and columns. The LOD for melatonin was 0.01 ng/mL. The method was successfully applied to the determination of melatonin in red and white wine, grape skin and plant extracts of Salvia officinalis L.

Dietary Sources and Bioactivities of Melatonin

“…The popular alcoholic drinks like beer [42,54] and wine [55,56], were tested for melatonin, with 0.09 ± 0.01 ng/mL in beer [42] and up to 129.5 ± 3.5 ng/mL in wine [42,54]. Besides the melatonin originated from the main ingredients, it was also considered to be synthesized during the fermentation process due to the yeast growth [54,57].…”

Recent applications of carbon-based nanomaterials in analytical chemistry: Critical review

“…Furthermore, the results were comparable to those obtained with single-wall CNT immobilized onto the capillary and showed significant improvements in resolution. Moreover, Stege et al [130] implemented a method for the determination of melatonin in complex food matrices by capillary electrochromatography with immobilized carboxylic multi-walled CNT as a stationary phase. The results showed high electrochromatographic resolution, good capillary efficiencies, and improved sensitivity with respect to those obtained with conventional capillaries.…”

Concentrations and profiles of melatonin and serotonin in fruits and vegetables during ripening: A mini-review

“…These melatonin levels are from ten to twenty fold higher than serotonin concentrations in the same fruit (a reversal of the common literature trends), and between five to almost eight orders of magnitude (0.005-4.0 ng·g -1 ) higher than grape skin concentrations reported by Iriti et al [23] in a survey of eight V. vinifera cultivars (Barbera, Croatina, Cabernet Sauvignon, Cabernet Franc, Marzemino, Nebbiolo, Sangiovese, and Merlot) and by Stege et al [24] in their examination of three V. vinifera cultivars (Malbec, Cabernet Sauvignon, and Chardonnay). The melatonin concentrations reported by Murch et al [22] also exceed by up to several orders of magnitude what appear to be the previous highest melatonin concentrations in plants and plant foods [11,12,14,25] reported for various medicinal herbs (<8,000 ng·g -1 ).…”

“…[10,26] We also expect melatonin to concentrate in the skin and seeds of grapes. Thus, with levels of melatonin in various seed types all <200 ng·g -1 , [27] good agreement by different research groups on grape skin melatonin contents near or below 1 ng·g -1 , [23,24] and finished wine concentrations of up to 0.5 ng·mL -1 , [24,28] whole grape concentrations of 100,000 to 200,000 ng·g -1 as reported by Murch et al do not seem reasonable. [22] Furthermore, the authors claim the highest melatonin concentrations were found at the early stage of veraison, yet a statistical reanalysis of their data shows there is no significant difference in mean concentrations between the four stages of development (p>0.45 by one-way ANOVA).…”