Aims: 

Antioxidants, both endogenous and dietary are involved in mechanisms to ensure cellular heath. We chose 3 established antioxidants, ascorbic acid, glutathione, melatonin to compare their protective effects in a DNA damage test by Comet assay.

Methods: 

The target cells were human lymphocytes incubated with hydrogen peroxide to induce a baseline DNA injury.

Results: 

We found that antioxidant property was dependent on the dose of the chemical used. At high concentrations, both dietary ascorbic acid and glutathione alone produced considerable DNA damage to the cells. This pro-oxidant effect was minimal when cells were treated with melatonin, a natural hormone released from the pineal gland.

Conclusion: 

The importance of dose-response relationships is highlighted when investigating any beneficial antioxidant effects in vitro. Also, the concentration of antioxidant used in bench assays ought to be matched with prescribed dose for dietary supplementation, assuming that absorption is adequate. Melatonin secretion is unique in that it peaks during sleep. A cellular protective effect for this nocturnal hormone could reflect its role in repair and regeneration during the period of daily rest. Melatonin may be a natural antioxidant produced by the brain.