Melatonin and Phytomelatonin: Chemistry, Biosynthesis, Metabolism, Distribution and Bioactivity in Plants and Animals—An Overview

Abstract

Melatonin is a ubiquitous indolamine, largely investigated for its key role in the regulation of several physiological processes in both animals and plants. In the last century, it was reported that this molecule may be produced in high concentrations by several species belonging to the plant kingdom and stored in specialized tissues. In this review, the main information related to the chemistry of melatonin and its metabolism has been summarized. Furthermore, the biosynthetic pathway characteristics of animal and plant cells have been compared, and the main differences between the two systems highlighted. Additionally, in order to investigate the distribution of this indolamine in the plant kingdom, distribution cluster analysis was performed using a database composed by 47 previously published articles reporting the content of melatonin in different plant families, species and tissues. Finally, the potential pharmacological and biostimulant benefits derived from the administration of exogenous melatonin on animals or plants via the intake of dietary supplements or the application of biostimulant formulation have been largely discussed.

Protective Role of Melatonin and Its Metabolites in Skin Aging

“…The levels of melatonin are regulated by its rapid metabolism in the liver or directly at the site of its synthesis in peripheral organs [158]. In the classical hepatic metabolism, CYP450 enzymes (CYP1A1, CYP1A2, and CYP1B1) degrade circulating melatonin to 6-OH-melatonin [159,160].…”

Revisiting the role of melatonin in human melanocyte physiology: A skin context perspective

“…Since melatonin synthesis, metabolism, signal transduction (Figure 1), target genes, and mechanisms of action have been extensively reviewed elsewhere, 86,96–99 it suffices to summarize here some salient features. Melatonin is synthesized in a multistep process from tryptophan 99 in the pineal gland and numerous “nonclassical,” extrapineal tissues in the human body such as skin and HFs (see below), 63,73 also in intact, wild‐type rodent (including mice) skin 58 .…”

“…82,83 Furthermore, the entire biochemical machinery necessary for transforming L-tryptophan into melatonin is expressed in all main tissue compartments of human skin, by epidermal and HF keratinocytes and melanocytes, dermal fibroblasts, and even mast cells. 60,[83][84][85] Since melatonin synthesis, metabolism, signal transduction (Figure 1), target genes, and mechanisms of action have been extensively reviewed elsewhere, 86,[96][97][98][99] it suffices to summarize here some salient features. Melatonin is synthesized in a multistep process from tryptophan 99 in the pineal gland and numerous "nonclassical," extrapineal tissues in the human body such as skin and HFs (see below), 63,73 also in intact, wild-type rodent (including mice) skin.…”

The phytomelatonin receptor PMTR1 regulates seed development and germination by modulating abscisic acid homeostasis in Arabidopsis thaliana

“…Melatonin (N-acetyl-5-methoxytrytamine [MLT]) is a tryptophan-derived indolamine and it acts as a wellknown protective agent in both animals and plants. [1][2][3][4][5] One of the important functions of MLT is that it can protect cells from various oxidants, including reactive oxygen species (ROS) and reactive nitrogen species (RNS). 6,7 Recently, mounting evidence has shown that MLT not only acts as an antioxidant but also triggers substantial changes in gene expression involved in diverse physiological processes, reflecting a pleiotropic role of MLT in organisms.…”