Difference Between Melanin and Melatonin

The key difference between melanin and melatonin is that melanin is one of the major pigments found in human skin, hair and eye, while melatonin is a hormone produced by the pineal gland and plays a role in somnolence and in the regulation of the sleep-wake cycle.

Melanin and melatonin are two chemically related substances, but with many different characteristic features. Their origin, function, chemical composition and location in the human body vary widely. Hence, this article attempts to discuss the difference between melanin and melatonin.

CONTENTS

1. Overview and Key Difference
2. What is Melanin 
3. What is Melatonin
4. Similarities Between Melanin and Melatonin
5. Side by Side Comparison – Melanin vs Melatonin in Tabular Form
6. Summary

What is Melanin?

Melanin is one of the major pigments found in human skin, which determines the skin colour. Its production occurs in melanocytes located in the skin, eye, ear, hair, and central nervous system of the human body. In addition to providing colour, melanin fulfils some other functions as well. Of those, the most important function is the protection of skin from solar UV radiation, which causes skin cancer in humans. Also, melanin shields the cell’s nuclei; thus, preventing DNA damage due to radiation. In addition, melanin has a role in hearing as well.

Besides, human melanin basically contains two polymers: eumelanin and pheomelanin. Eumelanin is dark brown/black coloured and its production occurs in eumelanosomes. Pheomelanin is red/yellow coloured and its production occurs in pheomelanosomes. Usually, the final colour of an individual’s skin depends on the type and amount of melanin produced and the shape, size, and, distribution of the melanosomes in the skin.

What is Melatonin?

Melatonin is a hormone produced mainly from the cells in the gastrointestinal tract, retina, and pineal gland. Melatonin is responsible for maintaining sleep-wake cycles, biological rhythms, and the modulation and inhibition of melanin synthesis. In addition, melatonin can repair damaged cells by stress and disease, and stop the secretion of MSH and ACTH hormones. Most importantly, melatonin is an antioxidant. It can destroy microorganisms by acting as a disease-fighting hormone.

Melatonin is one of the most complex molecules in the brain, liver, intestines, blood, and muscles. Melatonin originates from tryptophan, and catecholamines stimulate the synthesis and secretion of melatonin.

What are the Similarities Between Melanin and Melatonin?

• Melatonin and melanin are two substances present in living organisms.
• Amino acids produce both these substances.

What is the Difference Between Melanin and Melatonin?

The key difference between melanin and melatonin is that melanin is a pigment produced by tyrosine while melatonin is a hormone produced by tryptophan. Melanin provides skin colour and involves in photoprotection and hearing. On the other hand, melatonin has a major role in the modulation of the synthesis of melanin, maintaining the sleep-wake cycle and biological rhythms in the body. So, this is also a significant difference between melanin and melatonin.

Moreover, a further difference between melanin and melatonin is their synthesis. Melanin synthesis occurs in melanosomes found in melanocytes while melatonin synthesis occurs in the cells of the gastrointestinal tract, retina, and pineal gland. In addition, melanin is present in skin, eye, ear, hair, and central nervous system while melatonin is present in brain, liver, intestines, blood and muscles.

Summary – Melanin vs Melatonin

In brief, melanin and melatonin are two chemicals present in our body. Melanin is a pigment while melatonin is a hormone while amino acids are the precursor of both these molecules. Furthermore, melanin is a polymer while melatonin is not a polymer. Melanin is responsible for providing skin colour, photoprotection, and involves in hearing. On the other hand, melatonin is responsible for modulation of the synthesis of melanin, maintaining the sleep-wake cycle and biological rhythms in the body. Thus, this summarizes the difference between melanin and melatonin.

Reference:

1. “Melanin.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
2. “Melatonin.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.

Image Courtesy:

1. “Melanin” By ClickChemist – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Melatonin-structure” By phenida@PHENTANYL – Own work (Public Domain) via Commons Wikimedia