Melatonin: a hormone, a tissue factor, an autocoid, a paracoid, and an antioxidant vitamin

Authors

  • Dun-Xian Tan,

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA;
    2. Institute of Zoology and Anthropology, University of Göttingen, Göttingen, Germany
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  • Lucien C. Manchester,

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA;
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  • Rüdiger Hardeland,

    1. Institute of Zoology and Anthropology, University of Göttingen, Göttingen, Germany
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  • Silvia Lopez-Burillo,

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA;
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  • Juan C. Mayo,

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA;
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  • Rosa M. Sainz,

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA;
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  • Russel J. Reiter

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA;
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Address reprint requests to Russel J. Reiter, Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, Mail code 7762, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
E-mail: reiter@uthscsa.edu

Abstract

Abstract: Melatonin, a derivative of an essential amino acid, tryptophan, was first identified in bovine pineal tissue and subsequently it has been portrayed exclusively as a hormone. Recently accumulated evidence has challenged this concept. Melatonin is present in the earliest life forms and is found in all organisms including bacteria, algae, fungi, plants, insects, and vertebrates including humans. Several characteristics of melatonin distinguish it from a classic hormone such as its direct, non-receptor-mediated free radical scavenging activity. As melatonin is also ingested in foodstuffs such as vegetables, fruits, rice, wheat and herbal medicines, from the nutritional point of view, melatonin can also be classified as a vitamin. It seems likely that melatonin initially evolved as an antioxidant, becoming a vitamin in the food chain, and in multicellular organisms, where it is produced, it has acquired autocoid, paracoid and hormonal properties.

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