ABSTRACT
Melatonin (5-methoxy-N-acetyltryptamine), a derivative of the amino acid tryptophan, was rst discovered by Lerner and his coworkers (Lerner et al., 1958) as an endogenous neurohormone secreted by the pineal gland. However, later ndings revealed that melatonin is also synthesized by other tissues such as retina (Dubocovich, 1983), Harderian gland (Buzzell et al., 1990; Djeridane and Touitou, 2001), bone marrow (Conti et al., 2000), platelets (Champier et al., 1997), gastrointestinal tract (Bubenik, 2002), skin (Slominski et al., 2005), and lymphocytes (Carrillo-Vico et al., 2004). In addition to these extrapineal sources, a recent study demonstrated the synthesis of melatonin in the immature rat brains from fetal day 18 to the rst week of postnatal life, without any inuence from pineal gland (Jimenez-Jorge et al., 2007). Melatonin gained importance when it was identied to function as a chronobiotic substance regulating the circadian rhythms (Redman et al., 1983; Armstrong et al., 1986). Melatonin is known to participate in a wide range of physiological functions (Pandi-Perumal et al., 2006), to act as an antioxidant (Reiter et al., 2003) and an immune regulator (Carrillo-Vico et al., 2013) and has also been used in treating sleep disorders (Cummings, 2012; Ferracioli-Oda et al., 2013). Furthermore, it has been documented to have anticonvulsant action (Champney et al., 1996), antiaging property (Poeggeler, 2005), and oncostatic effect (Srinivasan et al., 2008).
