ABSTRACT
Melatonin is a ubiquitous natural substance that is widely distributed in nature, being found in both plants and animals [1-3]. Melatonin is probably one of the £rst biologically signi£cant compounds that appeared in living organisms. Although in all mammals including humans, melatonin is primarily synthesized in the pineal gland, its synthesis also occurs in other tissues, such as bone marrow, gut, gastrointestinal tract, lymphocytes, and in various parts of the eye in most mammals, i.e., the retina [4-6], the ciliary body [7], and the lachrymal gland [8].
