Deciphering the synthesis in Saccharomyces cerevisiae of the bioactives melatonin, serotonin, indoleacetic acid, hydroxytyrosol and tyrosol from glucose by using 13C labelling precursors and UHPLC-MS

Saccharomyces cerevisiae produces bioactive compounds such as melatonin (MEL), serotonin (SER), indoleacetic acid (IAA), hydroxytyrosol (HT), and tyrosol during alcoholic fermentation. Previous research shows that tryptophan and tyrosine are precursors. This study aimed to investigate whether S. cerevisiae can synthetize these bioactives from glucose. Using [U13C]-glucose as the fermentation substrate and UHPLC-MS for analysis, the research traced unequivocally the formation of these compounds. Results confirmed that MEL, SER, IAA, tyrosol, and HT are partly derived from glucose. Different 13C-labelled forms of HT, tyrosol, and tyrosine were identified which allows to propose a biosynthetic pathway leading to the formation of HT through reactions between intermediates from the pentose phosphate pathway, glycolysis, additionally to the Erlich pathway. The proposed pathway includes L-DOPA and catechol which were detected in their 13C-labelled forms. Understanding HT synthesis opens opportunities to enhance the bioactive potential of fermented beverages.