Melatonin (N-acetyl-5-methoxytryptamine) is an indolic compound derived from tryptophan. Usually identified as a neurotransmitter or animal hormone, this compound was detected in plants in 1995. Interest in knowing the melatonin content of plants and its possible role therein is growing, as indicated by the increasing number of related publications. Melatonin is present in all plant species studied, with large variations in its level depending on the plant organ or tissue. It seems to be more abundant in aromatic plants and in leaves than in seeds. Regarding its physiological function in plants, melatonin shows auxin activity and is an excellent antioxidant, regulating the growth of roots, shoots, and explants, activating seed germination and rhizogenesis (lateral- and adventitious-roots), and delaying induced leaf senescence. Its ability to strengthen plants subjected to abiotic stress such as drought, cold, heat, salinity, chemical pollutants, herbicides, and UV radiation makes melatonin an interesting candidate for use as a natural biostimulating substance for treating field crops. 1. Introduction Melatonin is a molecule endowed with a multitude of functions, particularly in mammals. This indoleamine is a hormone that acts in many physiological aspects, influencing mood, sleep, body temperature, the retina, and sexual behavior, among others. Most of these aspects are regulated through or in conjunction with the circadian clock present in animals [1–7]. In addition, melatonin is involved in numerous cellular actions as an antioxidant, acting as an excellent in vitro and in vivo free radical scavenger [8–15]. Chemically, melatonin (N-acetyl-5-methoxytryptamine) is an indolic compound derived from serotonin (5-hydroxytryptamine) (Figure 1). Both biogenic amines are synthesized from the amino acid tryptophan in a well-characterized biosynthetic pathway in animals and with some particular characteristics in plants. In plants, the auxin, indolyl-3-acetic acid (IAA), bears some resemblance to melatonin since both are indole compounds and have a common biosynthetic pathway through the compound tryptamine in the tryptophan-dependent IAA biosynthetic pathway (Figure 1). Figure 1: Molecular structure of melatonin and its related compounds in the biosynthesis pathway: tryptophan, serotonin, and tryptamine. This last compound is a precursor of the auxin indolyl-3-acetic acid, IAA. 2. Discovery of Melatonin in Plants The presence of melatonin was described for the first time in the bovine pineal gland by Lerner and coworkers [16]. The isolated substance was able
References
[1]
P. M. Fuller, J. J. Gooley, and C. B. Saper, “Neurobiology of the sleep-wake cycle: sleep architecture, circadian regulation, and regulatory feedback,” Journal of Biological Rhythms, vol. 21, no. 6, pp. 482–493, 2006.
[2]
J. E. Jan, R. J. Reiter, M. B. Wasdell, and M. Bax, “The role of the thalamus in sleep, pineal melatonin production, and circadian rhythm sleep disorders,” Journal of Pineal Research, vol. 46, no. 1, pp. 1–7, 2009.
[3]
E. Maronde and J. H. Stehle, “The mammalian pineal gland: known facts, unknown facets,” Trends in Endocrinology & Metabolism, vol. 18, no. 4, pp. 142–149, 2007.
[4]
R. Hardeland, “Melatonin in aging and disease—multiple consequences of reduced secretion, options and limits of treatment,” Aging and Disease, vol. 3, no. 2, pp. 194–225, 2012.
[5]
R. J. Reiter, “Melatonin: clinical relevance,” Best Practice & Research: Clinical Endocrinology & Metabolism, vol. 17, no. 2, pp. 273–285, 2003.
[6]
M. A. Zmijewski, T. W. Sweatman, and A. T. Slominski, “The melatonin-producing system is fully functional in retinal pigment epithelium (ARPE-19),” Molecular and Cellular Endocrinology, vol. 307, no. 1-2, pp. 211–216, 2009.
[7]
A. Slominski, D. J. Tobin, M. A. Zmijewski, J. Wortsman, and R. Paus, “Melatonin in the skin: synthesis, metabolism and functions,” Trends in Endocrinology & Metabolism, vol. 19, no. 1, pp. 17–24, 2008.
[8]
D.-X. Tan, R. Hardeland, L. C. Manchester et al., “The changing biological roles of melatonin during evolution: from an antioxidant to signals of darkness, sexual selection and fitness,” Biological Reviews, vol. 85, no. 3, pp. 607–623, 2010.
[9]
D.-X. Tan, L.-D. Chen, B. Poeggeler, L. C. Manchester, and R. J. Reiter, “Melatonin: a potent, endogenous hydroxyl radical scavenger,” Journal of Endocrinology, vol. 1, no. 4, pp. 57–60, 1993.
[10]
B. Poeggeler, R. J. Reiter, D.-X. Tan, L.-D. Chen, and L. C. Manchester, “Melatonin, hydroxyl radical-mediated oxidative damage, and aging: a hypothesis,” Journal of Pineal Research, vol. 14, no. 4, pp. 151–168, 1993.
[11]
R. J. Reiter, B. Poeggeler, D.-X. Tan, L.-D. Chen, L. C. Manchester, and J. M. Guerrero, “Antioxidant capacity of melatonin: a novel action not requiring a receptor,” Neuroendocrinology Letters, vol. 15, no. 1-2, pp. 103–116, 1993.
[12]
A. Galano, D.-X. Tan, and R. J. Reiter, “Melatonin as a natural ally against oxidative stress: a physicochemical examination,” Journal of Pineal Research, vol. 51, no. 1, pp. 1–16, 2011.
[13]
E. Gitto, D.-X. Tan, R. J. Reiter et al., “Individual and synergistic antioxidative actions of melatonin: studies with vitamin E, vitamin C, glutathione and desferrrioxamine (desferoxamine) in rat liver homogenates,” Journal of Pharmacy and Pharmacology, vol. 53, no. 10, pp. 1393–1401, 2001.
[14]
J. C. Mayo, D.-X. Tan, R. M. Sainz, M. Natarajan, S. López-Burillo, and R. J. Reiter, “Protection against oxidative protein damage induced by metal-catalyzed reaction or alkylperoxyl radicals: comparative effects of melatonin and other antioxidants,” Biochimica et Biophysica Acta, vol. 1620, no. 1–3, pp. 139–150, 2003.
[15]
R. J. Reiter, D.-X. Tan, L. C. Manchester, and W. Qi, “Biochemical reactivity of melatonin with reactive oxygen and nitrogen species: a review of the evidence,” Cell Biochemistry and Biophysics, vol. 34, no. 2, pp. 237–256, 2001.
[16]
A. B. Lerner, J. D. Case, Y. Takahashi, T. H. Lee, and W. Mori, “Isolation of melatonin, the pineal gland factor that lightens melanocytes,” Journal of the American Chemical Society, vol. 80, no. 10, pp. 2587–2592, 1958.
[17]
A. B. Lerner, J. D. Case, and R. V. Heinzelman, “Structure of melatonin,” Journal of the American Chemical Society, vol. 81, no. 22, pp. 6084–6085, 1959.
[18]
H. Weissbach, B. G. Redfield, and J. Axelrod, “Biosynthesis of melatonin: enzymic conversion of serotonin to N-acetylserotonin,” Biochimica et Biophysica Acta, vol. 43, pp. 352–353, 1960.
[19]
J. Axelrod and H. Weissbach, “Enzymatic O-methylation of N-acetylserotonin to melatonin,” Science, vol. 131, no. 3409, p. 1312, 1960.
[20]
A. B. Lerner, J. D. Case, W. Mori, and M. R. Wright, “Melatonin in peripheral nerve,” Nature, vol. 183, no. 4678, p. 1821, 1959.
[21]
J. K. Lauber, J. E. Boyd, and J. Axelrod, “Enzymatic synthesis of melatonin in avian pineal body: extraretinal response to light,” Science, vol. 161, no. 840, pp. 489–490, 1968.
[22]
P. C. Baker, W. B. Quay, and J. Axelrod, “Development of hydroxyindole-O-methyl transferase activity in eye and brain of the amphibian, Xenopus laevis,” Life Sciences, vol. 4, no. 20, pp. 1981–1987, 1965.
[23]
J. C. Fenwick, “Demonstration and effect of melatonin in fish,” General and Comparative Endocrinology, vol. 14, no. 1, pp. 86–97, 1970.
[24]
B. Vivien-Roels, P. Pévet, O. Beck, and M. Fevre-Montange, “Identification of melatonin in the compound eyes of an insect, the locust (Locusta migratoria), by radioimmunoassay and gas chromatography-mass spectrometry,” Neuroscience Letters, vol. 49, no. 1-2, pp. 153–157, 1984.
[25]
B. Vivien-Roels and P. Pévet, “Melatonin: presence and formation in invertebrates,” Experientia, vol. 49, no. 8, pp. 642–647, 1993.
[26]
M. Morita, F. Hall, J. B. Best, and W. Gern, “Photoperiodic modulation of cephalic melatonin in planarians,” Journal of Experimental Zoology, vol. 241, no. 3, pp. 383–388, 1987.
[27]
J. Callebert, J. Jaunay, and J. Jallon, “Control of Drosophilla biorhythms,” in Advances in Pineal Research, vol. 5, pp. 81–84, John Libbey, London, UK, 1991.
[28]
I. Balzer, I. R. Espínola, and B. Fuentes-Pardo, “Daily variations of immunoreactive melatonin in the visual system of crayfish,” Biology of the Cell, vol. 89, no. 8, pp. 539–543, 1997.
[29]
D. Abran, M. Anctil, and M. A. Ali, “Melatonin activity rhythms in eyes and cerebral ganglia of Aplysia californica,” General and Comparative Endocrinology, vol. 96, no. 2, pp. 215–222, 1994.
[30]
D. van Tassel and S. O'Neill, “Melatonin: identification of a potential dark signal in plants,” in Plant Physiology, vol. 102, supplement 1, article 659, 1993.
[31]
D. van Tassel, N. Roberts, and S. O'Neill, “Melatonin from higher plants: isolation and identification of N-acetyl-5-methoxytryptamine,” Plant Physiology, vol. 108, supplement 2, article 101, 1995.
[32]
R. Dubbels, R. J. Reiter, E. Klenke et al., “Melatonin in edible plants identified by radioimmunoassay and by high performance liquid chromatography-mass spectrometry,” Journal of Pineal Research, vol. 18, no. 1, pp. 28–31, 1995.
[33]
A. Hattori, H. Migitaka, M. Iigo et al., “Identification of melatonin in plants and its effects on plasma melatonin levels and binding to melatonin receptors in vertebrates,” Biochemistry and Molecular Biology International, vol. 35, no. 3, pp. 627–634, 1995.
[34]
J. Kolar, I. Machackova, H. Illnerova, E. Prinsen, W. van Dongen, and H. van Onckelen, “Melatonin in higher plant determined by radioimmunoassay and liquid chromatography-mass spectrometry,” Biological Rhythm Research, vol. 26, pp. 406–409, 1995.
[35]
R. J. Reiter, D.-X. Tan, S. Burkhardt, and L. C. Manchester, “Melatonin in plants,” Nutrition Reviews, vol. 59, no. 9, pp. 286–290, 2001.
[36]
J. Kolá？ and I. Machá？ková, “Melatonin in higher plants: occurrence and possible functions,” Journal of Pineal Research, vol. 39, no. 4, pp. 333–341, 2005.
[37]
C. Pape and K. Lüning, “Quantification of melatonin in phototrophic organisms,” Journal of Pineal Research, vol. 41, no. 2, pp. 157–165, 2006.
[38]
J. Cao, S. J. Murch, R. O'Brien, and P. K. Saxena, “Rapid method for accurate analysis of melatonin, serotonin and auxin in plant samples using liquid chromatography-tandem mass spectrometry,” Journal of Chromatography A, vol. 1134, no. 1-2, pp. 333–337, 2006.
[39]
R. Hardeland, S. Pandi-Perumal, and B. Poeggeler, “Melatonin in plants: focus on a vertebrate night hormone with cytoprotective properties.,” Functional Plant Science & Biotechnology, vol. 1, no. 1, pp. 32–45, 2007.
[40]
R. J. Reiter, L. C. Manchester, and D.-X. Tan, “Melatonin in walnuts: influence on levels of melatonin and total antioxidant capacity of blood,” Nutrition, vol. 21, no. 9, pp. 920–924, 2005.
[41]
S. Burkhardt, D.-X. Tan, L. C. Manchester, R. Hardeland, and R. J. Reiter, “Detection and quantification of the antioxidant melatonin in Montmorency and Balaton tart cherries (Prunus cerasus),” Journal of Agricultural and Food Chemistry, vol. 49, no. 10, pp. 4898–4902, 2001.
[42]
M. B. Arnao and J. Hernández-Ruiz, “Assessment of different sample processing procedures applied to the determination of melatonin in plants,” Phytochemical Analysis, vol. 20, no. 1, pp. 14–18, 2009.
[43]
M. B. Arnao and J. Hernández-Ruiz, “The physiological function of melatonin in plants,” Plant Signaling & Behavior, vol. 1, no. 3, pp. 89–95, 2006.
[44]
J. Hernández-Ruiz and M. B. Arnao, “Distribution of melatonin in different zones of lupin and barley plants at different ages in the presence and absence of light,” Journal of Agricultural and Food Chemistry, vol. 56, no. 22, pp. 10567–10573, 2008.
[45]
S. D. Paredes, A. Korkmaz, L. C. Manchester, D.-X. Tan, and R. J. Reiter, “Phytomelatonin: a review,” Journal of Experimental Botany, vol. 60, no. 1, pp. 57–69, 2009.
[46]
D.-X. Tan, R. Hardeland, L. C. Manchester et al., “Functional roles of melatonin in plants, and perspectives in nutritional and agricultural science,” Journal of Experimental Botany, vol. 63, no. 2, pp. 577–597, 2012.
[47]
X. Huang and G. Mazza, “Application of LC and LC-MS to the analysis of melatonin and serotonin in edible plants,” Critical Reviews in Food Science and Nutrition, vol. 51, no. 4, pp. 269–284, 2011.
[48]
M. C. Garcia-Parrilla, E. Cantos, and A. M. Troncoso, “Analysis of melatonin in foods,” Journal of Food Composition and Analysis, vol. 22, no. 3, pp. 177–183, 2009.
[49]
F. Gómez, I. G. Hernández, L. D. Martinez, M. F. Silva, and S. Cerutti, “Analytical tools for elucidating the biological role of melatonin in plants by LC-MS/MS,” Electrophoresis, vol. 34, no. 12, pp. 1749–1756, 2013.
[50]
D. L. van Tassel and S. D. O'Neill, “Putative regulatory molecules in plants: evaluating melatonin,” Journal of Pineal Research, vol. 31, no. 1, pp. 1–7, 2001.
[51]
R. Reiter, D.-X. Tan, L. Manchester et al., “Melatonin in edible plants (phytomelatonin): identification, concentrations, bioavailability and proposed functions,” World Review of Nutrition and Dietetics, vol. 97, pp. 211–230, 2007.
[52]
D. L. van Tassel, N. Roberts, A. Lewy, and S. D. O'Neill, “Melatonin in plant organs,” Journal of Pineal Research, vol. 31, no. 1, pp. 8–15, 2001.
[53]
G. Chen, Y. Huo, D.-X. Tan, Z. Liang, W. Zhang, and Y. Zhang, “Melatonin in Chinese medicinal herbs,” Life Sciences, vol. 73, no. 1, pp. 19–26, 2003.
[54]
J. Hernández-Ruiz, A. Cano, and M. B. Arnao, “Melatonin: a growth-stimulating compound present in lupin tissues,” Planta, vol. 220, no. 1, pp. 140–144, 2004.
[55]
M. B. Arnao, A. Cano, and M. Acosta, “Methods to measure the antioxidant activity in plant material. A comparative discussion,” Free Radical Research, vol. 31, pp. S89–S96, 1999.
[56]
M. B. Arnao, “Some methodological problems in the determination of antioxidant activity using chromogen radicals: a practical case,” Trends in Food Science & Technology, vol. 11, no. 11, pp. 419–421, 2000.
[57]
M. B. Arnao, A. Cano, and M. Acosta, “The hydrophilic and lipophilic contribution to total antioxidant activity,” Food Chemistry, vol. 73, no. 2, pp. 239–244, 2001.
[58]
A. Cano, M. Acosta, and M. B. Arnao, “Determination of antioxidant activity: an adaptation for measurement by HPLC,” in Encyclopedia of Chromatography, J. Cazes, Ed., pp. 1–6, Marcel Dekker Press, New York, NY, USA, 2002.
[59]
M. B. Arnao and J. Hernández-Ruiz, “Recommendations for determining antioxidant activity to study redox status and plant stress,” Plant Stress, vol. 1, pp. 32–36, 2007.
[60]
A. Cano, O. Alcaraz, and M. B. Arnao, “Free radical-scavenging activity of indolic compounds in aqueous and ethanolic media,” Analytical and Bioanalytical Chemistry, vol. 376, no. 1, pp. 33–37, 2003.
[61]
S. J. Murch, S. KrishnaRaj, and P. K. Saxena, “Tryptophan is a precursor for melatonin and serotonin biosynthesis in in vitro regenerated St. John's wort (Hypericum perforatum L. cv. Anthos) plants,” Plant Cell Reports, vol. 19, no. 7, pp. 698–704, 2000.
[62]
S. J. Murch and P. K. Saxena, “Melatonin: a potential regulator of plant growth and development?” In Vitro Cellular & Developmental Biology—Plant, vol. 38, no. 6, pp. 531–536, 2002.
[63]
I. Balzer and R. Hardeland, “Metatonin in algae and higher plants. Possible new roles as a phytohormone and antioxidant,” Botanica Acta, vol. 109, no. 3, pp. 180–183, 1996.
[64]
J. Hernández-Ruiz, A. Cano, and M. B. Arnao, “Melatonin acts as a growth-stimulating compound in some monocot species,” Journal of Pineal Research, vol. 39, no. 2, pp. 137–142, 2005.
[65]
J. Hernández-Ruiz and M. B. Arnao, “Melatonin stimulates the expansion of etiolated lupin cotyledons,” Plant Growth Regulation, vol. 55, no. 1, pp. 29–34, 2008.
[66]
Q. Chen, W.-B. Qi, R. J. Reiter, W. Wei, and B.-M. Wang, “Exogenously applied melatonin stimulates root growth and raises endogenous indoleacetic acid in roots of etiolated seedlings of Brassica juncea,” Journal of Plant Physiology, vol. 166, no. 3, pp. 324–328, 2009.
[67]
M. M. Posmyk, H. Kuran, K. Marciniak, and K. M. Janas, “Presowing seed treatment with melatonin protects red cabbage seedlings against toxic copper ion concentrations,” Journal of Pineal Research, vol. 45, no. 1, pp. 24–31, 2008.
[68]
M. B. Arnao and J. Hernández-Ruiz, “Melatonin promotes adventitious- and lateral root regeneration in etiolated hypocotyls of Lupinus albus L.,” Journal of Pineal Research, vol. 42, no. 2, pp. 147–152, 2007.
[69]
N. Zhang, B. Zhao, H. J. Zhang et al., “Melatonin promotes water-stress tolerance, lateral root formation, and seed germination in cucumber (Cucumis sativus L.),” Journal of Pineal Research, vol. 54, no. 1, pp. 15–23, 2013.
[70]
S. Park and K. Back, “Melatonin promotes seminal root elongation and root growth in transgenic rice after germination,” Journal of Pineal Research, vol. 53, no. 4, pp. 385–389, 2012.
[71]
V. N. Sarropoulou, I. N. Therios, and K. N. Dimassi-Theriou, “Melatonin promotes adventitious root regeneration in in vitro shoot tip explants of the commercial sweet cherry rootstocks CAB-6P (Prunus cerasus L.), Gisela 6 (P. cerasu canescens), and MxM 60 (P. aviu . mahaleb),” Journal of Pineal Research, vol. 52, no. 1, pp. 38–46, 2012.
[72]
R. Pelagio-Flores, E. Mu？oz-Parra, R. Ortiz-Castro, and J. López-Bucio, “Melatonin regulates Arabidopsis root system architecture likely acting independently of auxin signaling,” Journal of Pineal Research, vol. 53, no. 3, pp. 279–288, 2012.
[73]
F. Koyama, T. Carvalho, E. Alves et al., “The structurally related auxin and melatonin tryptophan-derivatives and their roles in Arabidopsis thaliana and in the human malaria parasite Plasmodium falciparum,” Journal of Eukaryotic Microbiology, vol. 60, no. 6, pp. 646–651, 2013.
[74]
M. B. Arnao and J. Hernández-Ruiz, “Protective effect of melatonin against chlorophyll degradation during the senescence of barley leaves,” Journal of Pineal Research, vol. 46, no. 1, pp. 58–63, 2009.
[75]
P. Wang, L. Yin, D. Liang, C. Li, F. Ma, and Z. Yue, “Delayed senescence of apple leaves by exogenous melatonin treatment: toward regulating the ascorbate-glutathione cycle,” Journal of Pineal Research, vol. 53, no. 1, pp. 11–20, 2012.
[76]
P. Wang, X. Sun, C. Li, Z. Wei, D. Liang, and F. Ma, “Long-term exogenous application of melatonin delays drought-induced leaf senescence in apple,” Journal of Pineal Research, vol. 54, no. 3, pp. 292–302, 2013.
[77]
V. Sarropoulou, K. Dimassi-Theriou, I. Therios, and M. Koukourikou-Petridou, “Melatonin enhances root regeneration, photosynthetic pigments, biomass, total carbohydrates and proline content in the cherry rootstock PHL-C (Prunus aviu runus cerasus),” Plant Physiology and Biochemistry, vol. 61, pp. 162–168, 2012.
[78]
D. Lazar, S. J. Murch, M. J. Beilby, and S. Al Khazaaly, “Exogenous melatonin affects photosynthesis in characeae Chara australis,” Plant Signaling & Behavior, vol. 8, no. 3, Article ID e23279, 2013.
[79]
R. J. Reiter, “The melatonin rhythm: both a clock and a calendar,” Experientia, vol. 49, no. 8, pp. 654–664, 1993.
[80]
J. Kolá？, I. Machá？ková, J. Eder et al., “Melatonin: occurrence and daily rhythm in Chenopodium rubrum,” Phytochemistry, vol. 44, no. 8, pp. 1407–1413, 1997.
[81]
K. Wolf, J. Kolá？, E. Witters, W. van Dongen, H. van Onckelen, and I. Machá？ková, “Daily profile of melatonin levels in Chenopodium rubrum L. depends on photoperiod,” Journal of Plant Physiology, vol. 158, no. 11, pp. 1491–1493, 2001.
[82]
D.-X. Tan, L. C. Manchester, P. di Mascio, G. R. Martinez, F. M. Prado, and R. J. Reiter, “Novel rhythms of N1-acetyl-N2-formyl-5- methoxykynuramine and its precursor melatonin in water hyacinth: importance for phytoremediation,” The FASEB Journal, vol. 21, no. 8, pp. 1724–1729, 2007.
[83]
H. E. Boccalandro, C. V. González, D. A. Wunderlin, and M. F. Silva, “Melatonin levels, determined by LC-ESI-MS/MS, fluctuate during the day/night cycle in Vitis vinifera cv Malbec: evidence of its antioxidant role in fruits,” Journal of Pineal Research, vol. 51, no. 2, pp. 226–232, 2011.
[84]
Y. Zhao, D.-X. Tan, Q. Lei et al., “Melatonin and its potential biological functions in the fruits of sweet cherry,” Journal of Pineal Research, vol. 55, no. 1, pp. 79–88, 2012.
[85]
O. Tal, A. Haim, O. Harel, and Y. Gerchman, “Melatonin as an antioxidant and its semi-lunar rhythm in green macroalga Ulva sp,” Journal of Experimental Botany, vol. 62, no. 6, pp. 1903–1910, 2011.
[86]
M. B. Arnao and J. Hernández-Ruiz, “Chemical stress by different agents affects the melatonin content of barley roots,” Journal of Pineal Research, vol. 46, no. 3, pp. 295–299, 2009.
[87]
M. B. Arnao and J. Hernández-Ruiz, “Growth conditions determine different melatonin levels in Lupinus albus L,” Journal of Pineal Research, vol. 55, no. 2, pp. 149–155, 2013.
[88]
D.-X. Tan, L. C. Manchester, P. Helton, and R. J. Reiter, “Phytoremediative capacity of plants enriched with melatonin,” Plant Signaling & Behavior, vol. 2, no. 6, pp. 514–516, 2007.
[89]
M. M. Posmyk, M. Ba？abusta, M. Wieczorek, E. Sliwinska, and K. M. Janas, “Melatonin applied to cucumber (Cucumis sativus L.) seeds improves germination during chilling stress,” Journal of Pineal Research, vol. 46, no. 2, pp. 214–223, 2009.
[90]
X.-Y. Lei, R.-Y. Zhu, G.-Y. Zhang, and Y.-R. Dai, “Attenuation of cold-induced apoptosis by exogenous melatonin in carrot suspension cells: the possible involvement of polyamines,” Journal of Pineal Research, vol. 36, no. 2, pp. 126–131, 2004.
[91]
Y. Zhao, L.-W. Qi, W.-M. Wang, P. K. Saxena, and C.-Z. Liu, “Melatonin improves the survival of cryopreserved callus of Rhodiola crenulata,” Journal of Pineal Research, vol. 50, no. 1, pp. 83–88, 2011.
[92]
K. Kang, K. Lee, S. Park, Y. S. Kim, and K. Back, “Enhanced production of melatonin by ectopic overexpression of human serotonin N-acetyltransferase plays a role in cold resistance in transgenic rice seedlings,” Journal of Pineal Research, vol. 49, no. 2, pp. 176–182, 2010.
[93]
S. Park, D.-E. Lee, H. Jang, Y. Byeon, Y.-S. Kim, and K. Back, “Melatonin-rich transgenic rice plants exhibit resistance to herbicide-induced oxidative stress,” Journal of Pineal Research, vol. 54, no. 3, pp. 258–263, 2013.
[94]
F. Afreen, S. M. A. Zobayed, and T. Kozai, “Melatonin in Glycyrrhiza uralensis: response of plant roots to spectral quality of light and UV-B radiation,” Journal of Pineal Research, vol. 41, no. 2, pp. 108–115, 2006.
[95]
M. B. Arnao and J. Hernández-Ruiz, “Growth conditions influence the melatonin content of tomato plants,” Food Chemistry, vol. 138, no. 2-3, pp. 1212–1214, 2013.
[96]
A. Conti, C. Tettamanti, M. Singaravel, C. Haldar, S. Pandi-Perumal, and G. Maestroni, “Melatonin: an ubiquitous and evolutionary hormone,” in Treatise on Pineal Gland and Melatonin, C. Haldar, M. Singaravel, and S. K. Maitra, Eds., pp. 105–143, Science Publishers, Enfield, UK, 2002.
[97]
M. M. Posmyk and K. M. Janas, “Melatonin in plants,” Acta Physiologiae Plantarum, vol. 31, no. 1, pp. 1–11, 2009.
[98]
K. M. Janas and M. M. Posmyk, “Melatonin, an underestimated natural substance with great potential for agricultural application,” Acta Physiologiae Plantarum, vol. 35, no. 12, pp. 3285–3292, 2013.
[99]
M. B. Arnao and J. Hernández-Ruiz, “Melatonin: synthesis from tryptophan and its role in higher plants,” in Amino Acids in Higher Plants, CAB Intern., J. DeMello, Ed., CAB International, Oxfordshire, UK, 2014.
[100]
L. C. Manchester, D.-X. Tan, R. J. Reiter, W. Park, K. Monis, and W. Qi, “High levels of melatonin in the seeds of edible plants: possible function in germ tissue protection,” Life Sciences, vol. 67, no. 25, pp. 3023–3029, 2000.
[101]
M. Sae-Teaw, J. Johns, N. P. Johns, and S. Subongkot, “Serum melatonin levels and antioxidant capacities after consumption of pineapple, orange, or banana by healthy male volunteers,” Journal of Pineal Research, vol. 55, no. 1, pp. 58–64, 2012.
[102]
P. Mena, á. Gil-Izquierdo, D. A. Moreno, N. Martí, and C. García-Viguera, “Assessment of the melatonin production in pomegranate wines,” LWT—Food Science and Technology, vol. 47, no. 1, pp. 13–18, 2012.
[103]
C. de la Puerta, M. P. Carrascosa-Salmoral, P. P. García-Luna et al., “Melatonin is a phytochemical in olive oil,” Food Chemistry, vol. 104, no. 2, pp. 609–612, 2007.
[104]
M. Stürtz, A. B. Cerezo, E. Cantos-Villar, and M. C. Garcia-Parrilla, “Determination of the melatonin content of different varieties of tomatoes (Lycopersicon esculentum) and strawberries (Fragaria ananassa),” Food Chemistry, vol. 127, no. 3, pp. 1329–1334, 2011.
[105]
D. González-Gómez, M. Lozano, M. F. Fernández-León, M. C. Ayuso, M. J. Bernalte, and A. B. Rodríguez, “Detection and quantification of melatonin and serotonin in eight Sweet Cherry cultivars (Prunus avium L.),” European Food Research and Technology, vol. 229, no. 2, pp. 223–229, 2009.
[106]
A. Ramakrishna, P. Giridhar, K. U. Sankar, and G. A. Ravishankar, “Melatonin and serotonin profiles in beans of Coffea species,” Journal of Pineal Research, vol. 52, no. 4, pp. 470–476, 2012.
[107]
M. Okazaki and H. Ezura, “Profiling of melatonin in the model tomato (Solanum lycopersicum L.) cultivar Micro-Tom,” Journal of Pineal Research, vol. 46, no. 3, pp. 338–343, 2009.
[108]
X. Huang and G. Mazza, “Simultaneous analysis of serotonin, melatonin, piceid and resveratrol in fruits using liquid chromatography tandem mass spectrometry,” Journal of Chromatography A, vol. 1218, no. 25, pp. 3890–3899, 2011.
[109]
M. Iriti, M. Rossoni, and F. Faoro, “Melatonin content in grape: myth or panacea?” Journal of the Science of Food and Agriculture, vol. 86, no. 10, pp. 1432–1438, 2006.
[110]
P. W. Stege, L. L. Sombra, G. Messina, L. D. Martinez, and M. F. Silva, “Determination of melatonin in wine and plant extracts by capillary electrochromatography with immobilized carboxylic multi-walled carbon nanotubes as stationary phase,” Electrophoresis, vol. 31, no. 13, pp. 2242–2248, 2010.
[111]
S. Vitalini, C. Gardana, A. Zanzotto et al., “The presence of melatonin in grapevine (Vitis vinifera L.) berry tissues,” Journal of Pineal Research, vol. 51, no. 3, pp. 331–337, 2011.
[112]
M. I. Rodriguez-Naranjo, A. Gil-Izquierdo, A. M. Troncoso, E. Cantos, and M. C. Garcia-Parrilla, “Melatonin: a new bioactive compound in wine,” Journal of Food Composition and Analysis, vol. 24, no. 4-5, pp. 603–608, 2011.
[113]
R. Zohar, I. Izhaki, A. Koplovich, and R. Ben-Shlomo, “Phytomelatonin in the leaves and fruits of wild perennial plants,” Phytochemistry Letters, vol. 4, no. 3, pp. 222–226, 2011.
[114]
S. J. Murch, C. B. Simmons, and P. K. Saxena, “Melatonin in feverfew and other medicinal plants,” The Lancet, vol. 350, no. 9091, pp. 1598–1599, 1997.
[115]
F. Marioni, A. Bertoli, and L. Pistelli, “A straightforward procedure to biosynthesise melatonin using freshly chopped Achillea millefolium L. as reagent,” Phytochemistry Letters, vol. 1, no. 2, pp. 107–110, 2008.
[116]
S. J. Murch and P. K. Saxena, “A melatonin-rich germplasm line of St John's wort (Hypericum perforatum L.),” Journal of Pineal Research, vol. 41, no. 3, pp. 284–287, 2006.
[117]
P. Pothinuch and S. Tongchitpakdee, “Melatonin contents in mulberry (Morus spp.) leaves: effects of sample preparation, cultivar, leaf age and tea processing,” Food Chemistry, vol. 128, no. 2, pp. 415–419, 2011.
[118]
S. Park, T.-N. N. Le, Y. Byeon, Y. S. Kim, and K. Back, “Transient induction of melatonin biosynthesis in rice (Oryza sativa L.) during the reproductive stage,” Journal of Pineal Research, vol. 55, no. 1, pp. 40–45, 2013.
[119]
A. P. Simopoulos, D.-X. Tan, L. C. Manchester, and R. J. Reiter, “Purslane: a plant source of omega-3 fatty acids and melatonin,” Journal of Pineal Research, vol. 39, no. 3, pp. 331–332, 2005.
[120]
S. J. Murch, A. R. Alan, J. Cao, and P. K. Saxena, “Melatonin and serotonin in flowers and fruits of Datura metel L,” Journal of Pineal Research, vol. 47, no. 3, pp. 277–283, 2009.
