History of Melatonin Discovery

 

Melatonin was first extracted and discovered from the pineal gland of cow by the dermatologist Aron B Lerner at the Yale University of School of Medicine. This purified product was chemically identified as N-acetyl-5-methoxy-tryptamine and is termed as Melatonin. One of the characteristic of the chemical is that it is mainly secreted during darkness and hence it is also known as hormone of darkness1. In the subsequent years melatonin has also been identified in many plants and a wide variety of animals. Presence of melatonin in a wide variety of bacteria gives an emphasis that this chemical is an ancient molecule that has been retained throughout the evolutionary process of all organisms. Primitive bacteria like cyanobacteria and α-proteobacteria are thought to be engulfed by the prokaryotes and they evolved into chloroplasts and mitochondria so that all the unicellular and multicellular organelles produce this indolamine into their organelles. With the evolutionary process the melatonin spread among all the organisms and are processed by evolution with vivid functions and actions.  Initial functions of the melatonin were to detoxify free radicals but with the evolutionary changes it adapts the functions related to stress reducer and having anti-inflammatory effects. The biosynthetic enzymes for melatonin have been found in several genes of many species. For the multiple functions of the melatonin in organisms they had developed several mechanisms to generate the biosynthesis process.

            Molecular oxygen level began to rise in the earth’s atmospheric layer due to persistent release of oxygen by the photosynthetic bacteria persisting in the earth’s atmosphere billions of years ago. The rise of oxygen level in the earth’s atmosphere is used by different bacteria for several metabolism purposes. Reactive oxygen species are generated during aerobic metabolism when oxygen accepts leaked electron from the electron transport chain. These ROS are very toxic in nature for the cells and the organelles and to neutralize this melatonin has been evolved as a free radical scavenger and as an anti-oxidant. Melatonin reacts with wide verities of ROS to produce 3-hydroxymelatonin and other metabolites and these metabolites have the capacity to act as free radical scavengers and also have the capacity to neutralize toxic effects of ROS. The chemical structure of the melatonin remains unchanged despite long evolutionary process. Despite having the preliminary scavenging function of free radicals of the melatonin, evolutionary changes brought the face of new dimension and showed variable effects of the molecule in maintaining the circadian rhythm. Good amount of melatonin were consumed by the primitive plants and animals for the detoxification process during day time. In complex organisms it has been seen that for several functional effects a signaling molecule was adopted during the dark phase and hence melatonin cycle system was adopted as signaling system for carrying out several detoxification process because these complex organisms has no longer been able to respond the melatonin effects in the photoperiod2.

            Multicellular animals opted the phenomenon of producing more melatonin during the night time thereby ensuring day-light phenomenon. This results in the development of pineal gland which is responsible for the secretion of melatonin and enhancing day light circle. Photosensitive relation between the eye and pineal gland is clearly understood by carrying out many researches in the understanding of neural connectivity and anatomy thus ensuing the mechanism by which melatonin is secreted by the pineal gland and many neurotransmitters and chemicals also responds in this current phenomenon is known after gravious study and research. In mammals the functional activity of the melatonin reflects the hormonal activity and property and it can be ascertained by the fact that melatonin is responsible for maintaining the reproductive activity, maintaining the physiology of sleep, anti aging property, immunoresponsive effects and cellular metabolism2.

Sources:-

1.Melatonin: Fifty Years of Scientific Journey from the Discovery in Bovine Pineal Gland to Delineation of Functions in Human, Indrajit Chowdhury, Anamika Sengupta and Saumen Kumar Maitra, https://www.researchgate.net/publication/23650746_Melatonin_Fifty_Years_of_Scientific_Journey_from_the_Discovery_in_Bovine_Pineal_Gland_to_Delineation_of_Functions_in_Human

2. Melatonin synthesis and function: Evolutionary history in animals and plants, Dake Zaho, Yang yu, Yong shen, Qin Liu, Zhiwei Zhao, Ramaswamy Sharma, Russel J Reiter, https://www.researchgate.net/publication/332852118_Melatonin_Synthesis_and_Function_Evolutionary_History_in_Animals_and_Plants

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