The effect of variations in pH and temperature on stability of melatonin in aqueous solution

Melatonin (N-acetyl-5-methoxytryptamine) has a diverse range of functions, including the control of neuroendocrine events. A number of studies have sh own that melatonin may be of potential benefit for the treatment of insomni a, as well as neurodegenerative disorders. At present, there are numerous d osage forms of melatonin, with the oral route of administration being most popular. Presently, there is little information on the stability of melaton in over a pH range. With the changes in pH in the gastro-intestinal tract, as well as in different experimental conditions, information on the stabili ty of melatonin would be important. We used a high-performance liquid chrom atography method to determine the stability of melatonin solutions over a p H range (1.2-12) at room temperature and at 37 degreesC over a period of 21 days. The results show that no melatonin degradation occurred in the first 2 days. From days 3 to 21, there was a gradual decline in melatonin at all pHs, with the decline not exceeding 30%. No decline in melatonin levels oc curred in the first 2 days at 37 degreesC. From days 3 to 21, melatonin lev els declined gradually, with the decline not exceeding 29%.