Emergence of naturally occurring melatonin isomers and their proposed nomenclature

Abstract

: Melatonin was considered to be the sole member of this natural family. The emergence of naturally occurring melatonin isomers (MIs) has opened an exciting new research area. Currently, several MIs have been identified in wine, and these molecules are believed to be synthesized by either yeasts or bacteria. A tentative nomenclature for the MIs is proposed in this article. It will be important to explore whether all organisms have the capacity to synthesize MIs, especially under the conditions of environmental stress. These isomers probably share many of the biological functions of melatonin, but their activities seem to exceed those of melatonin. On basis of the limited available information, it seems that MIs differ in their biosynthetic pathways from melatonin. Especially in those compounds in which the aliphatic side chain is not attached to ring atom 3, the starting material may not be tryptophan. Also, the metabolic pathways of MIs remain unknown. This, therefore, is another promising area of research to explore. It is our hypothesis that MIs would increase the performance of yeasts and probiotic bacteria during the processes of fermentation. Therefore, yeasts producing elevated levels of these isomers might have a superior alcohol tolerance and be able to produce higher levels of alcohol. This can be tested by comparing existing yeast strains differing in alcohol tolerance. Selection for MIs may become a strategy for isolating more resistant yeast and Lactobacillus strains, which can be of interest for industrial alcohol production and quality improvements in bacterially fermented foods such as kimchi.

Melatonin, an underestimated natural substance with great potential for agricultural application

“…This process is described as the free radical scavenging cascade, which makes MEL highly effective, even at low concentrations, in protecting organisms from oxidative stress (Galano et al 2013). Evidence supports the conclusion that plants and plant products contain isomers of this indoleamine which may be also ROS scavengers (Tan et al 2012b;Vitalini et al 2013). MEL reduces oxidative damage of important molecules and its antioxidant activity may manifest itself in several ways: (i) direct free radical scavenging; (ii) elevating the antioxidant enzyme activity; (iii) protecting antioxidant enzymes from oxidative damage; (iv) increasing the efficiency of the mitochondrial transport chain and (v) reducing the generation of free radicals (Tan et al 2010).…”

Melatonin: Exceeding Expectations

“…Isomers of melatonin have been identified in plant products (19,65), and we have predicted they will eventually be found throughout the plant and animal kingdoms (60). Isomers are molecules with the identical molecular size as melatonin; they also possess the same methoxy residue and the aliphatic side chain as melatonin itself, but they are in different locations on the indole nucleus.…”

A new balancing act: The many roles of melatonin and serotonin in plant growth and development

“…Additionally, though much research has been done to investigate the presence and activity of MEL in plants, new analytical technologies have led to the identification of many possible isomers of MEL, which have not been studied in depth 45 compound in the protection of plants against stresses which were recently reviewed by several authors including refs 42,46,47 and include biotic stresses such as pathogen attack and diverse abiotic stresses including drought, freezing, osmotic, heat, heavy metal, UV and oxidative stresses; 5HT has some similar actions in some plant species 42,[47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] .…”