Melatonin scavenges phenylglyoxylic ketyl radicals.
The antioxidant properties of melatonin were tested in this work by EPR technique. It was found that melatonin scavenges phenylglyoxylic ketyl radicals. Its effectiveness was 10-times lower than that of vitamin C. A new method of generation of phenylglyoxylic ketyl radicals by spontaneous decomposition of D,L-2,3-diphenyltartaric acid in propan-2-ol was used.
Melatonin and the Pineal Gland
&NA; The pineal gland is an enigma within the central nervous system that appears to exert tremendous control over the homeostatic mechanisms of the body. In the animal kingdom, the pineal gland and the hormone it produces, melatonin, regulate circadian rhythms, sleep‐wake cycles, thermal and immunologic systems, and reproductive capability. Human research has demonstrated that the pineal gland also plays a role in sleep disturbances, menstrual and reproductive irregularities, psychological and behavioral disorders, and may even serve as a tumor inhibitory gland. Although research is still in the early stages, it is apparent that the pineal gland and melatonin have widespread effects and optimal functioning of the pineal gland is essential to our well‐being.
Melatonin‐Induced Suppression of Human Lymphocyte Natural Killer Activity in Vitro
One of the important immune functions influenced by neuroendocrine factors is natural killer (NK) activity, which is directed against neoplastic and virus‐infected cells. The effects of melatonin (Mel) and N‐acetylserotonin (NAc‐5HT) on NK activity of human peripheral blood lymphocytes were investigated. Leukocytes of healthy human subjects were used in the experiment. NK activity was estimated by measurement of radioactive chromium (51Cr) release from human leukemia cells K 562 (target cells). The previous exposure of human lymphocytes (effector cells) to Mel in concentrations of 10−6 M and 10l0 M resulted in an inhibition of NK activity (P < 0.01) for all the examined effector‐target cell ratios (10:1; 20:1, 40:1). NK activity was also suppressed by Mel (108 M), but only if effector‐target ratio equal to 20:1 was used (P < 0.02), and by Mel (10−12 M) for effector‐target ratio equal to 40:1 (P < 0.05). In none of the examined concentrations did NAc‐5HT inhibit NK activity of human lymphocytes. On the basis of the data reported above, a direct suppressive effect of Mel (but not of NAc‐5HT) on NK activity of human peripheral blood lymphocytes can be assumed.