High levels of melatonin generated during the brewing process

Engineering a GPCR-based yeast biosensor for a highly sensitive melatonin detection from fermented beverages

Melatonin is a multifunctional molecule with diverse biological roles that holds great value as a health-promoting bioactive molecule in any food product and yeast's ability to produce it has been extensively demonstrated in the last decade. However, its quantification presents costly analytical challenges due to the usual low concentrations found as the result of yeast metabolism. This study addresses these analytical challenges by optimizing a yeast biosensor based on G protein-coupled receptors (GPCR) for melatonin detection and quantitation. Strategic genetic modifications were employed to significantly enhance its sensitivity and fluorescent signal output, making it suitable for detection of yeast-produced melatonin. The optimized biosensor demonstrated significantly improved sensitivity and fluorescence, enabling the screening of 101 yeast strains and the detection of melatonin in various wine samples. This biosensor's efficacy in quantifying melatonin in yeast growth media underscores its utility in exploring melatonin production dynamics and potential applications in functional food development. This study provides a new analytical approach that allows a rapid and cost-effective melatonin analysis to reach deeper insights into the bioactivity of melatonin in fermented products and its implications for human health. These findings highlight the broader potential of biosensor technology in streamlining analytical processes in fermentation science.

The melatonin contained in beer can provide health benefits, due to its antioxidant, anti-inflammatory and immunomodulatory properties

Beer is a fermented beverage with a low alcohol content originating from cereal fermentation (barley or wheat). It forms part of the diet for many people. It contains melatonin (N-acetyl-5-methoxytryptamine). Melatonin is a molecule with a wide range of antioxidant, oncostatic, immunomodulatory, and cytoprotective properties. The aim of this work was to review the data supporting the idea that a moderate consumption of beer, because of its melatonin content, is particularly useful in healthy diets and in other physiological situations (such as pregnancy, menopause, and old age). Data source: a) The MEDLINE /PubMed search was conducted from 1975 to April 2022, and b) Our own experience and published studies on melatonin, the immune system, and beer. We provide a review of research on the mechanisms of melatonin generation in beer, its concentrations, and its possible effects on health. The melatonin contained in beer, as part of a healthy diet and in some special physiological situations, could act as a protective factor and improve the quality of life of those who drink it in moderation. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Role of the PAA1 Gene on Melatonin Biosynthesis in Saccharomyces cerevisiae: A Search of New Arylalkylamine N-Acetyltransferases

Recently, the presence of melatonin in fermented beverages has been correlated with yeast metabolism during alcoholic fermentation. Melatonin, originally considered a unique product of the pineal gland of vertebrates, has been also identified in a wide range of invertebrates, plants, bacteria, and fungi in the last two decades. These findings bring the challenge of studying the function of melatonin in yeasts and the mechanisms underlying its synthesis. However, the necessary information to improve the selection and production of this interesting molecule in fermented beverages is to disclose the genes involved in the metabolic pathway. So far, only one gene has been proposed as involved in melatonin production in Saccharomyces cerevisiae, PAA1, a polyamine acetyltransferase, a homolog of the vertebrate's aralkylamine N-acetyltransferase (AANAT). In this study, we assessed the in vivo function of PAA1 by evaluating the bioconversion of the different possible substrates, such as 5-methoxytryptamine, tryptamine, and serotonin, using different protein expression platforms. Moreover, we expanded the search for new N-acetyltransferase candidates by combining a global transcriptome analysis and the use of powerful bioinformatic tools to predict similar domains to AANAT in S. cerevisiae. The AANAT activity of the candidate genes was validated by their overexpression in E. coli because, curiously, this system evidenced higher differences than the overexpression in their own host S. cerevisiae. Our results confirm that PAA1 possesses the ability to acetylate different aralkylamines, but AANAT activity does not seem to be the main acetylation activity. Moreover, we also prove that Paa1p is not the only enzyme with this AANAT activity. Our search of new genes detected HPA2 as a new arylalkylamine N-acetyltransferase in S. cerevisiae. This is the first report that clearly proves the involvement of this enzyme in AANAT activity.

The potential role of yeasts in the mitigation of health issues related to beer consumption

Food consumption of healthier products has become an essential trend in the food sector. This is also the case in beer, a biochemical process of transformation performed by yeast cells. More and more studies proclaim the need to reduce ethanol content in alcoholic drinks, certainly the most important health issue of beer consumption. In this review we gather key health issues related to beer consumption and the last advances regarding the use of yeast to attenuate those health problems. Furthermore, we have included the latest findings about the general positive impact of yeast in health as a consequence of its ability to biotransform polyphenolic compounds present in the wort, producing healthy compounds as hydroxytyrosol or melatonin, and its ability to perform as a probiotic driver. Besides, a group of population with chronic diseases as diabetes or celiac disease could take advantage of low carbohydrate or gluten-free beers, respectively. The role of yeast in beer production has been traditionally associated to its fermentative power. But here we have found a change in this dogma in the last years toward yeasts being a main driver to enhance healthy aspects of beer. The key findings are discussed and possible future directions are proposed.

Impact of Non-Saccharomyces Wine Yeast Strains on Improving Healthy Characteristics and the Sensory Profile of Beer in Sequential Fermentation

The use of non-Saccharomyces yeasts in brewing is a useful tool for developing new products to meet the growing consumer demand for innovative products. Non-Saccharomyces yeasts can be used both in single and in mixed fermentations with Saccharomyces cerevisiae, as they are able to improve the sensory profile of beers, and they can be used to obtain functional beers (with a low ethanol content and melatonin production). The aim of this study was to evaluate this capacity in eight non-Saccharomyces strains isolated from Madrid agriculture. For this purpose, single fermentations were carried out with non-Saccharomyces strains and sequential fermentations with non-Saccharomyces and the commercial strain SafAle S-04. The Wickerhamomyces anomalus strain CLI 1028 was selected in pure culture for brewing beer with a low ethanol content (1.25% (v/v)) for its fruity and phenolic flavours and the absence of wort flavours. The best-evaluated strains in sequential fermentation were CLI 3 (Hanseniaspora vineae) and CLI 457 (Metschnikowia pulcherrima), due to their fruity notes as well as their superior bitterness, body, and balance. Volatile compounds and melatonin production were analysed by GC and HPLC, respectively. The beers were sensory-analysed by a trained panel. The results of the study show the potential of non-Saccharomyces strains in the production of low-alcohol beers, and as a flavour enhancement in sequential fermentation.

Function, Mechanism, and Application of Plant Melatonin: An Update with a Focus on the Cereal Crop, Barley (Hordeum vulgare L.)

Melatonin is a multiple-function molecule that was first identified in animals and later in plants. Plant melatonin regulates versatile processes involved in plant growth and development, including seed germination, root architecture, flowering time, leaf senescence, fruit ripening, and biomass production. Published reviews on plant melatonin have been focused on two model plants: (1) Arabidopsis and (2) rice, in which the natural melatonin contents are quite low. Efforts to integrate the function and the mechanism of plant melatonin and to determine how plant melatonin benefits human health are also lacking. Barley is a unique cereal crop used for food, feed, and malt. In this study, a bioinformatics analysis to identify the genes required for barley melatonin biosynthesis was first performed, after which the effects of exogenous melatonin on barley growth and development were reviewed. Three integrated mechanisms of melatonin on plant cells were found: (1) serving as an antioxidant, (2) modulating plant hormone crosstalk, and (3) signaling through a putative plant melatonin receptor. Reliable approaches for characterizing the function of barley melatonin biosynthetic genes and to modulate the melatonin contents in barley grains are discussed. The present paper should be helpful for the improvement of barley production under hostile environments and for the reduction of pesticide and fungicide usage in barley cultivation. This study is also beneficial for the enhancement of the nutritional values and healthcare functions of barley in the food industry.

Wine Saccharomyces Yeasts for Beer Fermentation

Multiple studies in recent years have shown the potential of Saccharomyces wild yeasts to produce craft beers with new flavour profiles and other desirable properties. Yeasts isolated from food (wine, bread, kombucha…) have shown potential promise for application in brewing. The aim of this study is to evaluate the ability of 141 Saccharomyces yeast strains isolated from the Madrilenian agriculture (from grapes, must, wine, vineyard, and cellars) to produce a novel ale beer. Fermentation activity of the strains was compared against the commercial strain Saccharomyces cerevisiae Safale S-04. In addition to the other aspects such as melatonin production, thirty-three volatile compounds belonging to higher alcohols, esters, aldehydes/cetones, acids, lactones and phenolic groups, were analysed by GC for selection of the strains. Ten strains were finally chosen, among which the most relevant was the strain G 520 showing a higher production of esters, higher alcohols and acids compared with S-04. The apparent attenuation for this strain was lower than commercial strain, which translates into more residual sugars. Furthermore, G 520 was more capable of producing significantly higher amounts of melatonin studied by HPLC, as well as showing a higher antioxidant capacity. Consumer study showed that G 520 strain could be used to produce a potential beer that has a place in the current market.

Plant-derived melatonin from food: a gift of nature

In recent years, people have become increasingly interested in bioactive ingredients from plants, especially antioxidant molecules such as melatonin, which are beneficial to human health. The purpose of this article is to provide new information on plant-derived foods with a high content of melatonin. We comprehensively summarize the content of melatonin in plant-derived foods and discuss the factors that influence melatonin levels to provide new ideas on enhancement. Additionally, we describe the biosynthetic pathway of melatonin and identify its major functions. Medicinal herbs are often rich in melatonin while many vegetables and fruits exhibit somewhat lower levels with wide variations among species. The genetic traits of plants, the phenological stage of the cultivar, the photoperiod, the level of stress to which the plants are exposed at the time of harvest, exposure to agrochemicals and determination methods are the main factors affecting the melatonin content. To date, standardization of uniform sampling times and the use of suitable pretreatments as well as determination methods have not been achieved. The results of the studies reviewed highlight the potentially important role of plant melatonin in influencing the progression of human diseases. Based on the health promotional aspects of melatonin, consuming foods containing higher concentrations of tryptophan and melatonin is suggested.

Naturally occurring melatonin: Sources and possible ways of its biosynthesis

According to recent reports, the global market for melatonin is worth 700 million USD in 2018 and would reach 2,790 million USD by 2025, growing at a CAGR of 18.9% during 2019 to 2025. Having regard to the prevalence of sleep and circadian rhythm disorders and a clear tendency to increase the demand for melatonin, and the current lack of alternative green and cost-efficient technologies of its synthesis, the supply of this remedy will not be enough to guarantee melatonin supply and affordability on a global scale. The emergence of naturally occurring melatonin and its isomers in fermented foods has opened an exciting new research area; there are still, however, some obscure points in the efficient microbiological biosynthesis of melatonin. This review summarizes the research progress and recent evidence related to melatonin and its isomers in various foodstuffs. Additionally, one possible way to synthesize melatonin is also discussed. The evidence pointed out that the presence of melatonin and its isomers is not exclusive for grapes and grape-derived products, because it can be also found in sweet and sour cherries. However, different species of both Saccharomyces and non-Saccharomyces yeasts could be used to obtain melatonin and melatonin isomers in the process of alcoholic fermentation biotechnologically. The availability of L-tryptophan has been a key factor in determining the concentration of indolic compounds produced, and the utilization of probiotic lactic acid bacteria could help in the formation of melatonin isomers during malolactic fermentation. These approaches are environmentally friendly alternatives with a safer profile than conventional ones and could represent the future for sustainable industrial-scale melatonin production.

Occurrence of melatonin and indolic compounds derived from l-tryptophan yeast metabolism in fermented wort and commercial beers

Melatonin and serotonin are bioactive compounds present in foods and beverages and related to neuroprotection and anti-angiogenesis, among other activities. They have been described in wines and the role of yeast in their formation is clear. Thus, this study evaluates the content of these bioactives and other related indolic compounds in beer. For this purpose, commercial beers were analyzed by a validated UHPLC-HRMS method and sample treatment optimized due to the low concentrations expected. Moreover, a wort was fermented with different commercial beer yeast (Abbaye, Diamond, SafAle, SafLager) in order to monitor the formation of these bioactives during the elaboration process. Results show that indolic compounds such as N-acetylserotonin and 3-indoleacetic acid are produced during the alcoholic fermentation of wort. Moreover, the occurrence of four indolic compounds (5-hydroxytryptophan, N-acetylserotonin, 3-indoleacetic acid, l-tryptophan ethyl ester) in commercial beers is reported for the first time.

Effect of Several Nutrients and Environmental Conditions on Intracellular Melatonin Synthesis in Saccharomyces cerevisiae

Melatonin is a bioactive compound that is present in fermented beverages and has been described to be synthesized by yeast during alcoholic fermentation. The aim of this study was to assess the capacity of intracellular and extracellular melatonin production by different Saccharomyces strains from diverse food origin and to study the effects of different fermentation parameters, such as sugar and nitrogen concentration, temperature or initial population, on melatonin production using a synthetic grape must medium. Melatonin from fermentation samples was analyzed by liquid chromatography mass spectrometry. Intracellular melatonin synthesis profile did not present differences between yeast strains. However, extracellular melatonin production depended on the yeast origin. Thus, we suggest that melatonin production and secretion during the different yeast growth phases follows a species-specific pattern. Other parameters that affected the fermentation process such as sugar content and low temperature had an impact on intracellular melatonin production profile, as well as the melatonin content within the cell. This study reports the effect of several conditions on the melatonin synthesis profile, highlighting its possible role as a signal molecule.

Microorganisms: Producers of Melatonin in Fermented Foods and Beverages

Melatonin has recently been detected in fermented beverages and foods, in which microorganism metabolism is highly important. The existing literature knowledge discusses the direction for future studies in this review. Evidence shows that many species of microorganisms could synthesize melatonin. However, the actual concentrations of melatonin in fermented foods and beverages range from picograms per milliliter to nanograms per milliliter. Different types of microorganisms, different raw materials, different culture environments, the presence or absence of precursors, high or low alcohol content, and different detection methods are all possible reasons for the huge difference of melatonin levels. Thus far, there have been relatively few studies on the melatonin synthesis pathway microorganisms. Thus, referring to the synthetic pathway of plants and animals, the putative melatonin biosynthesis pathway of microorganisms is presented. It will be significant to discuss whether all species of microorganisms have the capacity to synthesize melatonin and what the biological functions of melatonin are in microorganisms. Melatonin plays a lot of important roles in microorganisms, particularly in enhancing the tolerance of environment stress. Also, the loss of melatonin concentration in commercially available fermented foods and beverages is a ubiquitous trend, and how to solve this problem is a new field to be further explored.

Development of a Phytomelatonin-Rich Extract from Cultured Plants with Excellent Biochemical and Functional Properties as an Alternative to Synthetic Melatonin

Melatonin is a pleiotropic molecule with multiple and various functions. In recent years, there has been a considerable increase in the consumption of melatonin supplements for reasons other than those related with sleep (as an antioxidant, for anti-aging, and as a hunger regulator). Although the chemical synthesis of melatonin has recently been improved, several unwanted by-products of the chemical reactions involved occur as contaminants. Phytomelatonin, melatonin of plant origin, was discovered in several plants in 1995, and the possibility of using raw plant material as a source to obtain dietary supplements rich in phytomelatonin instead of synthetic melatonin, with its corresponding chemical by-products was raised. This work characterizes the phytomelatonin-rich extract obtained from selected plant material and determines the contents in phytomelatonin, phenols, flavonoids, and carotenoids. Additionally, the antioxidant activity was measured. Finally, a melatonin-specific bioassay in fish was carried out to demonstrate the excellent biological properties of the natural phytomelatonin-rich extract obtained.

Melatonin and glycolytic protein interactions are related to yeast fermentative capacity

Melatonin is an indole amine that interacts with some proteins in mammals, such as calreticulin, calmodulin or sirtuins. In yeast, melatonin is synthetized and interacts with glycolytic proteins during alcoholic fermentation in Saccharomyces cerevisiae. Due to its importance as an antioxidant molecule in both Saccharomyces and non-Saccharomyces yeasts, the aim of this study was to determine the intracellular and extracellular synthesis profiles of melatonin in four non-Saccharomyces strains (Torulaspora delbrueckii, Hanseniaspora uvarum, Starmeralla bacillaris and Metschnikowia pulcherrima) and to confirm whether glycolytic enzymes can also interact with this molecule in non-conventional yeast cells. Melatonin from fermentation samples was analyzed by liquid chromatography mass spectrometry, and proteins bound to melatonin were immunopurified by melatonin-IgG-Dynabeads. Melatonin was produced in a similar pattern in all non-Saccharomyces yeast, with M. pulcherrima and S. bacillaris being the highest producers. However, melatonin only bound to proteins in two non-conventional yeasts, S. bacillaris and T. delbrueckii, which specifically had higher fermentative capacities. Sequence analysis showed that most proteins shared high levels of homology with glycolytic enzymes, but an RNA-binding protein, the elongation alpha factor, which is related to mitochondria, was also identified. This study reports for the first time the interaction of melatonin with proteins inside non-Saccharomyces yeast cells. These results reinforce the possible role of melatonin as a signal molecule, likely related to fermentation metabolism and provide a new perspective for understanding its role in yeast.

Neuroactive compounds in foods: Occurrence, mechanism and potential health effects

Neuroactive compounds are synthesized by certain plants and microorganisms by undertaking different tasks, especially as a stress response. Most common neuroactive compounds in foods are gamma-aminobutyric acid (GABA), serotonin, melatonin, kynurenine, kynurenic acid, dopamine, norepinephrine, histamine, tryptamine, tyramine and β-phenylethylamine. Fermented foods contain some of these compounds, which can affect human health and mood. Moreover, food processing such as roasting and malting alter amount and profile of neuroactive compounds in foods. In addition to plant-origin and microbially-formed neuroactive compounds in foods, these substances are also formed by gut microbiota, which is the most attractive subject to assess the interaction between gut microbiota and mental health. The discovery of microbiota-gut-brain axis calls for the investigation of the effects of diet on the formation of neuroactive compounds in the gut. Furthermore, probiotics and prebiotics are indispensable elements for the understanding of the food-mood relationship. The focus of this comprehensive review is to investigate the neuroactive compounds found naturally in foods or formed during fermentation. Their formation pathways in humans, plants and microorganisms, potential health effects, effects of diet on the formation of microbial metabolites including neuroactive compounds in the gut are discussed throughout this review. Furthermore, the importance of gut-brain axis, probiotics and prebiotics are discussed.

Deciphering the melatonin metabolism in Saccharomyces cerevisiae by the bioconversion of related metabolites

Melatonin (Mel), originally considered a neurohormone, has been detected in beverages and food-fermented products in which yeast metabolism is highly important. This indolamine is synthesized from serotonin, with L-tryptophan being the initial substrate of both. Regarding Mel metabolism, the biosynthetic pathway in mammals consists in four-step reactions. However, six genes are implicated in the synthesis of Mel in plants, which suggest the presence of many pathways. The aim of this study was to provide new empirical data on the production of Mel and other indole-related compounds in the yeast Saccharomyces cerevisiae (S. cerevisiae). To this end, we performed the addition of the pathway intermediates in S. cerevisiae cells in different growth stages (exponential and arrested cells) to follow the bioconversion and new indolic compound production from them. The different bioconverted indolic compounds tested (L-tryptophan, 5-hydroxytryptophan, tryptamine, serotonin, N-acetylserotonin, 5-methoxytryptamine, and Mel) were analyzed by UHPLC-MS/MS from the extra- and intracellular contents. Our results showed that serotonin, in yeast, was prevalently formed via tryptophan decarboxylation, followed by tryptamine hydroxylation as in plants. Mel production from serotonin can be achieved by either N-acetylation, followed by O-methylation or O-methylation, in turn followed by N-acetylation. Accordingly, the classic pathway of Mel synthesis in vertebrates does not seems prevalent in yeast.

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 µg/L). The proposed method proved to be suitable for assessing the investigated compounds in some red wine samples, where 74.4⁻256.2 µg/L and 0.038⁻0.063 µg/L of TEE and MEL were detected, respectively. Five MISs were also found in wine samples in concentrations up to 1.97 µg/L.

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

La melatonina (MEL) è un'indolammina implicata nella regolazione dei cicli circadiani e che possiede attività antiossidante. La presenza di MEL è stata dimostrata nelle piante e negli alimenti con particolare attenzione agli alimenti e bevande fermentati, tra cui il vino. L'uva è una fonte di MEL e nel vino l'attività metabolica del lievito svolge un ruolo cruciale per la produzione di MEL. È stato recentemente suggerito che anche i batteri lattici (LAB) posseggano tale abilità. In questo studio è 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 è emerso che nei vini prodotti in due delle quattro cantine è 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 quantità 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. The contribution of lactic bacteria on melatonin in red wine

Promising Antineoplastic Actions of Melatonin

Melatonin is an endogenous indoleamine with an incredible variety of properties and activities. In recent years, an increasing number of studies have investigated this indoleamine’s interaction with cancerous cells. In particular, it seems that melatonin not only has the ability to improve the efficacy of many drugs used in chemotherapy but also has a direct inhibitory action on neoplastic cells. Many publications underlined the ability of melatonin to suppress the proliferation of various cancer cells or to modulate the expression of membrane receptors on these cells, thereby reducing tumor aggressiveness to metastasize. In addition, while melatonin has antiapoptotic actions in normal cells, in many cancer cells it has proapoptotic effects; these dichotomous actions have gained the interest of researchers. The increasing focus on melatonin in the field of oncology and the growing number of studies on this topic require a deep understanding of what we already know about the antineoplastic actions of melatonin. This information would be of value for potential use of melatonin against neoplastic diseases.

Dietary Melatonin Supplementation Could Be a Promising Preventing/Therapeutic Approach for a Variety of Liver Diseases

In the therapeutic strategies, the role of diet is a well-established factor that can also have an important role in liver diseases. Melatonin, identified in animals, has many antioxidant properties and it was after discovered also in plants, named phytomelatonin. These substances have a positive effect during aging and in pathological conditions too. In particular, it is important to underline that the amount of melatonin produced by pineal gland in human decreases during lifetime and its reduction in blood could be related to pathological conditions in which mitochondria and oxidative stress play a pivotal role. Moreover, it has been indicated that melatonin/phytomelatonin containing foods may provide dietary melatonin, so their ingestion through balanced diets could be sufficient to confer health benefits. In this review, the classification of liver diseases and an overview of the most important aspects of melatonin/phytomelatonin, concerning the differences among their synthesis, their presence in foods and their role in health and diseases, are summarized. The findings suggest that melatonin/phytomelatonin supplementation with diet should be considered important in preventing different disease settings, in particular in liver. Currently, more studies are needed to strengthen the potential beneficial effects of melatonin/phytomelatonin in liver diseases and to better clarify the molecular mechanisms of action.

Melatonin: Protection against age-related cardiac pathology

Aging is a complex and progressive process that involves physiological and metabolic deterioration in every organ and system. Cardiovascular diseases are one of the most common causes of mortality and morbidity among elderly subjects worldwide. Most age-related cardiovascular disorders can be influenced by modifiable behaviours such as a healthy diet rich in fruit and vegetables, avoidance of smoking, increased physical activity and reduced stress. The role of diet in prevention of various disorders is a well-established factor, which has an even more important role in the geriatric population. Melatonin, an indoleamine with multiple actions including antioxidant properties, has been identified in a very large number of plant species, including edible plant products and medical herbs. Among products where melatonin has been identified include wine, olive oil, tomato, beer, and others. Interestingly, consumed melatonin in plant foods or melatonin supplementation may promote health benefits by virtue of its multiple properties and it may counteract pathological conditions also related to cardiovascular disorders, carcinogenesis, neurological diseases and aging. In the present review, we summarized melatonin effects against age-related cardiac alterations and abnormalities with a special focus on heart ischemia/reperfusion (IR) injury and myocardial infarction.

Dietary Sources and Bioactivities of Melatonin

Insomnia is a serious worldwide health threat, affecting nearly one third of the general population. Melatonin has been reported to improve sleep efficiency and it was found that eating melatonin-rich foods could assist sleep. During the last decades, melatonin has been widely identified and qualified in various foods from fungi to animals and plants. Eggs and fish are higher melatonin-containing food groups in animal foods, whereas in plant foods, nuts are with the highest content of melatonin. Some kinds of mushrooms, cereals and germinated legumes or seeds are also good dietary sources of melatonin. It has been proved that the melatonin concentration in human serum could significantly increase after the consumption of melatonin containing food. Furthermore, studies show that melatonin exhibits many bioactivities, such as antioxidant activity, anti-inflammatory characteristics, boosting immunity, anticancer activity, cardiovascular protection, anti-diabetic, anti-obese, neuroprotective and anti-aging activity. This review summaries the dietary sources and bioactivities of melatonin, with special attention paid to the mechanisms of action.

Are the proposed benefits of melatonin-rich foods too hard to swallow?

Melatonin has been proposed as a potent anti-oxidant, and its presence in many plants and foods has been suggested to be beneficial for health. Indeed, the concentrations of melatonin in blood and the melatonin metabolite 6 sulphatoxymelatonin in urine have been found to increase significantly after ingestion of melatonin-rich foods. In this review, the studies have been critically evaluated in light of the reported plant melatonin concentrations and our knowledge of pharmacokinetics of orally administered pure melatonin. In the case of studies involving measurement of plasma melatonin following ingestion of beer or fruits, the reported increase in melatonin is not consistent with the amount of melatonin ingested. Similarly, the amount of melatonin metabolite excreted following ingestion of melatonin-rich foods greatly exceeded the amount of melatonin ingested. It is concluded that studies reporting the appearance of melatonin in blood and its metabolites in urine following ingestion of melatonin-rich foods are flawed. While there may be health benefits for certain foods, it is difficult to accept that these are due to their low melatonin content.

On the significance of an alternate pathway of melatonin synthesis via 5-methoxytryptamine: comparisons across species

Melatonin is a phylogenetically ancient molecule. It is ubiquitously present in almost all organisms from primitive photosynthetic bacteria to humans. Its original primary function is presumable to be that of an antioxidant with other functions of this molecule having been acquired during evolution. The synthetic pathway of melatonin in vertebrates has been extensively studied. It is common knowledge that serotonin is acetylated to form N-acetylserotonin by arylalkylamine N-acetyltransferase (AANAT) or arylamine N-acetyltransferase (SNAT or NAT) and N-acetylserotonin is, subsequently, methylated to melatonin by N-acetylserotonin O-methyltransferase (ASMT; also known as hydroxyindole-O-methyltransferase, HIOMT). This is referred to as a classic melatonin synthetic pathway. Based on new evidence, we feel that this classic melatonin pathway is not generally the prevailing route of melatonin production. An alternate pathway is known to exist, in which serotonin is first O-methylated to 5-methoxytryptamine (5-MT) and, thereafter, 5-MT is N-acetylated to melatonin. Here, we hypothesize that the alternate melatonin synthetic pathway may be more important in certain organisms and under certain conditions. Evidence strongly supports that this alternate pathway prevails in some plants, bacteria, and, perhaps, yeast and may also occur in animals.

CSF generation by pineal gland results in a robust melatonin circadian rhythm in the third ventricle as an unique light/dark signal

Pineal gland is an important organ for the regulation of the bio-clock in all vertebrate species. Its major secretory product is melatonin which is considered as the chemical expression of darkness due to its circadian peak exclusively at night. Pineal melatonin can be either released into the blood stream or directly enter into the CSF of the third ventricle via the pineal recess. We have hypothesized that rather than the peripheral circulatory melatonin circadian rhythm serving as the light/dark signal, it is the melatonin rhythm in CSF of the third ventricle that serves this purpose. This is due to the fact that melatonin circadian rhythm in the CSF is more robust in terms of its extremely high concentration and its precise on/off peaks. Thus, extrapineal-generated melatonin or diet-derived melatonin which enters blood would not interfere with the bio-clock function of vertebrates. In addition, based on the relationship of the pineal gland to the CSF and the vascular structure of this gland, we also hypothesize that pineal gland is an essential player for CSF production. We feel it participates in both the formation and reabsorption of CSF. The mechanisms associated with these processes are reviewed and discussed in this brief review.

Melatonin in Mediterranean diet, a new perspective

The health-promoting properties of the Mediterranean diet have been attributed, at least in part, to the chemical diversity of plant foods. Among phytochemicals, polyphenols represent the paradigm of the relationship between healthy foods and reduced risk of chronic-degenerative diseases, although, in the past few years, a new element has enriched this scenario. Melatonin, and possibly other indoleamines recently discovered in some relevant Mediterranean foods, may represent a new factor contributing to the elucidation of the protective effects of diets rich in plant products. Therefore, in synergy with polyphenols and other bioactive phytochemicals (e.g. carotenoids and glucosinolates), melatonin may contribute to maximizing the benefits of healthy dietary styles. This brief survey deals with the occurrence of melatonin in the Mediterranean diet, with an emphasis on grape products, and focuses on the biological significance of dietary melatonin, an emerging and exciting topic in the field of nutritional sciences.

Yeast contribution to melatonin, melatonin isomers and tryptophan ethyl ester during alcoholic fermentation of grape musts

Melatonin (MEL) has been found in some medicinal and food plants, including grapevine, a commodity of particular interest for the production of wine, a beverage of economic relevance. It has also been suggested that MEL in wine may, at least in part, contribute to the health-promoting properties attributed to this beverage and, possibly, to other traditional Mediterranean foodstuffs. After a preliminary screening of 9 yeast strains in laboratory medium, three selected strains (Saccharomyces cerevisiae EC1118, Torulaspora delbrueckii CBS1146(T) and Zygosaccharomyces bailii ATCC36947(T) ) were inoculated in experimental musts obtained from 2 white (Moscato and Chardonnay) and 2 red (Croatina and Merlot) grape varieties. The production of MEL, melatonin isomers (MIs) and tryptophan ethyl ester (TEE) was monitored during the alcoholic fermentation. The screening showed that the three investigated strains produced the highest concentrations of MEL and two MIs in optimal growth conditions. However, MEL and MIs were not produced in oenological conditions, but the three strains synthesized high concentrations of a new MI and TEE in musts.

Tryptophan-ethylester, the false (unveiled) melatonin isomer in red wine

Among the food plants, the presence of melatonin in grapes (Vitis vinifera L.) deserves particular attention because of the production of wine, an alcoholic beverage of economic relevance and with putative healthy effects. Furthermore, melatonin isomers have been detected in wine too. Recently, one of these isomers has been identified as tryptophan-ethylester, a compound with the same molecular weight of melatonin. In this Commentary, we briefly comment the source(s) of tryptophan-ethylester in wine and the putative nutritional role(s).

'Melatonin isomer' in wine is not an isomer of the melatonin but tryptophan-ethylester

Melatonin is a neurohormone, chronobiotic, and antioxidant compound found in wine and deriving directly from grapes and/or synthesized by yeast during alcoholic fermentation. In addition, a melatonin isomer has been detected in different foods, wine among them. The special interest for melatonin isomer related to the fact that it was found in greater quantities than melatonin and probably shares some of its biological properties. Despite this, its chemical structure has not yet been defined; although some researchers hypothesize, it could be melatonin with the ethylacetamide group shifted into position N1. Thus, the aim of our study was to identify the structures of the melatonin isomer. For this purpose, melatonin and melatonin isomer in Syrah wine were separated chromatographically by a sub-2 μm particle column and detected by tandem mass spectrometry. The sample was then purified and concentrated by solid-phase extraction, hydrolyzed with alkali or esterase, and substrates and products quantified by UPLC-MS/MS. Moreover, melatonin, melatonin isomer, and their product ions were evaluated by high-resolution mass spectrometry. The amount of melatonin isomer and melatonin in the wine was 84 ± 4 and 3 ± 0 ng/mL, respectively. In the solutions, containing diluted alkali or esterase, melatonin isomer was hydrolyzed in about 8 min. Correspondingly, tryptophan was detected, and its amount increased and reached the maximum concentration in about 8 min. Melatonin concentration was not affected by diluted alkali or esterase. The fragmentation pattern of melatonin isomer was different from that of melatonin but comparable to that of tryptophan-ethylester. Finally, the so-called melatonin isomer identity was verified by cochromatography with authentic standard of tryptophan-ethylester.

Formation of melatonin and its isomer during bread dough fermentation and effect of baking

Melatonin is produced mainly by the pineal gland in vertebrates. Also, melatonin and its isomer are found in foods. Investigating the formation of melatonin and its isomer is of importance during bread dough fermentation and its degradation during baking since bread is widely consumed in high amounts. Formation of melatonin was not significant during dough fermentation. The melatonin isomer content of nonfermented dough was found to be 4.02 ng/g and increased up to 16.71 ng/g during fermentation. Lower amounts of isomer in crumb and crust than dough showed that the thermal process caused a remarkable degree of degradation in melatonin isomer. At the end of the 180 min fermentation Trp decreased by 58%. The results revealed for the first time the formation of a melatonin isomer in bread dough during yeast fermentation.

Alcoholic fermentation induces melatonin synthesis in orange juice

Melatonin (N-acetyl-5-methoxytryptamine) is a molecule implicated in multiple biological functions. Its level decreases with age, and the intake of foods rich in melatonin has been considered an exogenous source of this important agent. Orange is a natural source of melatonin. Melatonin synthesis occurs during alcoholic fermentation of grapes, malt and pomegranate. The amino acid tryptophan is the precursor of all 5-methoxytryptamines. Indeed, melatonin appears in a shorter time in wines when tryptophan is added before fermentation. The aim of the study was to measure melatonin content during alcoholic fermentation of orange juice and to evaluate the role of the precursor tryptophan. Identification and quantification of melatonin during the alcoholic fermentation of orange juice was carried out by UHPLC-QqQ-MS/MS. Melatonin significantly increased throughout fermentation from day 0 (3.15 ng/mL) until day 15 (21.80 ng/mL) reaching larger amounts with respect to other foods. Melatonin isomer was also analysed, but its content remained stable ranging from 11.59 to 14.18 ng/mL. The enhancement of melatonin occurred mainly in the soluble fraction. Tryptophan levels significantly dropped from 13.80 mg/L (day 0) up to 3.19 mg/L (day 15) during fermentation. Melatonin was inversely and significantly correlated with tryptophan (r = 0.907). Therefore, the enhancement in melatonin could be due to both the occurrence of tryptophan and the new synthesis by yeast. In summary, the enhancement of melatonin in novel fermented orange beverage would improve the health benefits of orange juice by increasing this bioactive compound.