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Open AccessArticle

LC-MS/MS-Based Profiling of Tryptophan-Related Metabolites in Healthy Plant Foods

1
Department of Agricultural and Environmental Sciences, Università degli Studi di Milano, 20133 Milan, Italy
2
Department of Health Sciences, Università degli Studi di Milano, 20142 Milan, Italy
3
Department of Food, Environmental and Nutritional Sciences, Università degli Studi di Milano, 20133 Milan, Italy
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Academic Editor: Paula B. Andrade
Molecules 2020, 25(2), 311; https://doi.org/10.3390/molecules25020311
Received: 1 December 2019 / Revised: 30 December 2019 / Accepted: 8 January 2020 / Published: 13 January 2020
Food plants contain hundreds of bioactive phytochemicals arising from different secondary metabolic pathways. Among these, the metabolic route of the amino acid Tryptophan yields a large number of plant natural products with chemically and pharmacologically diverse properties. We propose the identifier “indolome” to collect all metabolites in the Tryptophan pathway. In addition, Tryptophan-rich plant sources can be used as substrates for the fermentation by yeast strains to produce pharmacologically active metabolites, such as Melatonin. To pursue this technological development, we have developed a UHPLC-MS/MS method to monitor 14 Tryptophan, Tryptamine, amino-benzoic, and pyridine metabolites. In addition, different extraction procedures to improve the recovery of Tryptophan and its derivatives from the vegetal matrix were tested. We investigated soybeans, pumpkin seeds, sesame seeds, and spirulina because of their botanical diversity and documented healthy effects. Four different extractions with different solvents and temperatures were tested, and water extraction at room temperature was chosen as the most suitable procedure to extract the whole Tryptophan metabolites pattern (called by us “indolome”) in terms of ease, high efficiency, short time, low cost, and sustainability. In all plant matrices, Tryptophan was the most abundant indole compound, while the pattern of its metabolites was different in the diverse plants extracts. Overall, 5-OH Tryptamine and Kynurenine were the most abundant compounds, despite being 100–1000-fold lower than Tryptophan. Melatonin was undetected in all extracts, but sesame showed the presence of a Melatonin isomer. The results of this study highlight the variability in the occurrence of indole compounds among diverse food plants. The knowledge of Tryptophan metabolism in plants represents a relevant issue for human health and nutrition. View Full-Text
Keywords: Tryptophan; Tryptamine; indole compounds; matrix extraction; soya; Pumpkin; Sesame; Spirulina; nutraceuticals; functional foods; mass spectrometry Tryptophan; Tryptamine; indole compounds; matrix extraction; soya; Pumpkin; Sesame; Spirulina; nutraceuticals; functional foods; mass spectrometry
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MDPI and ACS Style

Vitalini, S.; Dei Cas, M.; Rubino, F.M.; Vigentini, I.; Foschino, R.; Iriti, M.; Paroni, R. LC-MS/MS-Based Profiling of Tryptophan-Related Metabolites in Healthy Plant Foods. Molecules 2020, 25, 311.

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