Il contributo dei batteri lattici per la presenza di melatonina nel vino rosso

La melatonina (MEL) e un\u2019indolammina implicata nella regolazione dei cicli circadiani e che ` possiede attivita antiossidante. La presenza di MEL ` e stata dimostrata nelle piante e negli alimenti con ` particolare attenzione agli alimenti e bevande fermentati, tra cui il vino. L\u2019uva e una fonte di MEL e nel ` vino l\u2019attivita metabolica del lievito svolge un ruolo cruciale per la produzione di MEL. ` E stato recentemente ` suggerito che anche i batteri lattici (LAB) posseggano tale abilita. In questo studio ` e stata indagata la sintesi ` di MEL da parte dei LAB in condizioni enologiche e di laboratorio. Sono stati analizzati 8 vini rossi prodotti su scala industriale in 4 cantine. Inoltre, 11 ceppi di LAB sono stati inoculati in terreno sintetico simil-vino. Dai risultati ottenuti e emerso che nei vini prodotti in due delle quattro cantine ` e stato osservato un aumento ` di MEL al termine della fermentazione malolattica. Tutti i ceppi oggetto dello studio hanno prodotto MEL in condizioni di laboratorio in quantita variabile a seconda del ceppo. I risultati mettono in evidenza per la ` prima volta che i LAB sono capaci di rilasciare MEL sia in condizioni di laboratorio che nel vino prodotto industrialmente.Melatonin (MEL) is an indolamine regulating the circadian rhythms and acting as antioxidant. The presence of MEL has been evidenced in plants and foods with particular attention to fermented foods and beverages, such as wine. Grape is a source of MEL and in wine the metabolic activity of yeast is crucial for MEL production. It has been recently suggested that the lactic acid bacteria (LAB) have also this ability. In this study, the LAB-mediated production of MEL was investigated in both oenological and laboratory conditions. For this purpose, 8 red wines produced in industrial scale in 4 wineries were analysed. Moreover, 11 LAB strains were inoculated in synthetic-wine, a synthetic medium. The results showed that the concentrations of MEL increased in the wines produced in two out of four wineries at the end of the malolactic fermentation. All the investigated strains produced MEL in laboratory conditions at different levels depending to the strain itself. Our results highlighted for the first time the LABs are able to synthetize MEL in both oenological and laboratory conditions

Assessment of tryptophan, tryptophan ethylester, and melatonin derivatives in red wine by SPE-HPLC-FL and SPE-HPLC-MS methods

Melatonin (MEL) is an indoleamine produced mainly by the pineal gland in vertebrates. It plays a significant role in the regulation of circadian rhythms, mitigation of sleeping disorders, and jet lag. This compound is synthetized from tryptophan (TRP) and it has been found in seeds, fruits, and fermented beverages, including wine. Wine is also a source of other tryptophan derivatives, the tryptophan ethylester (TEE) and MEL isomers (MISs), for which the biological properties need to be elucidated. An analytical method for the simultaneous quantification of TRP, TEE, and MEL was developed by a Solid Phase Extraction (SPE) of a preconcentration of wine followed by high performance liquid chromatography (HPLC) analysis either with fluorescence or mass spectrometer detectors. The analytical method showed a relative standard deviation (RSD) lower than 8%, except for TRP (RSD 10.5% in wine). The recovery was higher than 76%. The versatility of SPE preconcentrations allowed for the adequate preconcentration of wine sample as well as detection of low concentrations, an important aspect especially for MEL (detection limit 0.0023 \ub5g/L). The proposed method proved to be suitable for assessing the investigated compounds in some red wine samples, where 74.4-256.2 \ub5g/L and 0.038-0.063 \ub5g/L of TEE and MEL were detected, respectively. Five MISs were also found in wine samples in concentrations up to 1.97 \ub5g/L

Production of melatonin and other tryptophan derivatives by Oenococcus oeni under winery and laboratory scale

Malolactic fermentation (MLF) in Valtellina Superiore DOCG red wine was monitored in 4 cellars and the final products were analysed to determine the content of melatonin (MEL) and other tryptophan (TRP) derivatives, including tryptophan ethyl ester (TEE) and MEL isomers (MISs), and to isolate predominant O. oeni strains. MEL and TEE significantly increased in wines after MLF from two cellars out of four. Six strains were isolated during the MLF of red wines and under laboratory scale, in rich and synthetic wine cultural media, together with other four O. oeni strains able to trigger the MLF. Results showed that the presence of stressful growth factors, like ethanol and acid pH, has a pivotal role in triggering the release of TEE by oenococci. Indeed, all the strains became capable to produce also MEL and MISs, together with TEE. under harsh growth conditions, as in a synthetic wine medium. The production of these compounds was strain-dependent and a maximum amount of 0.0078\u202f\ub1\u202f0.0023 ngT/mL (UMB472) and 619.85\u202f\ub1\u202f196.16 ngT/mL (UMB436) of MEL and TEE was obtained, respectively. In particular, different MISs were detected under oenological and laboratory scale suggesting that other factors (i.e. technological and/or physico-chemical) could affect the synthesis of TRP derivatives