This 2020 review subject was melatonin:

“The emergence of naturally occurring melatonin and its isomers in fermented foods has opened an exciting new research area. Melatonin is a hormone, an indolamine that predominantly appears in plants, microorganisms, and mammals.

The precursor of this molecule is solely the amino acid L‐tryptophan. Melatonin ensures a circadian and seasonal signal to vertebrate organisms; it is synthesized through a cascade of enzymatic reactions producing melatonin from serotonin in its final phases. The synthesis of melatonin is observed in almost all organs.

One melatonin molecule has the capacity to scavenge up to 10 ROS versus the other antioxidants that scavenge 1 or even less ROS. Melatonin antioxidant properties are accomplished with the indole ring that stimulates enzyme production (i.e., superoxide dismutase (SOD), glutathione‐peroxidase (Gpx), and catalase (CAT)), which mitigate free radicals to less toxic substances.

In addition to antioxidant properties, it plays a fundamental role in the modulation of various physiological functions, including circadian rhythmicity, bone integrity, and functionalization of the human reproductive system.

The presence of melatonin and its isomers is not exclusive for grapes and grape‐derived products. Other fruits such as sweet and sour cherries and fermented juices of orange and pomegranate may be also of interest.”

https://onlinelibrary.wiley.com/doi/full/10.1111/1541-4337.12639 “Naturally occurring melatonin: Sources and possible ways of its biosynthesis”