Research: SIU and colleagues, De

Listed in Issue 34


SIU and colleagues, Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong studied how melatonin and vitamin E antioxidants protect cells from the damaging effects of free radicals.



The authors compared the effect of melatonin and vitamin E against lipid peroxidation (LOP) in rat retinal homogenates, in order to characterise the antioxidative efficacy of melatonin in the retina, a tissue highly sensitive to oxidative damage. Malondialdehyde (MDA) was used to provide an index of cell damage in vitro.


Levels of lipid peroxidation products were significantly reduced in a dose-response manner by all concentrations of vitamin E and melatonin, in concentrations of both 2.0 or 4.0 mM, significantly reduced LOP. Vitamin E treatment always yielded a lower level of LPO products than did the same concentration of melatonin. The concentrations of each agent required to inhibit 50% of the lipid damage (IC50) were 0.69 mM and 4.98 mM for vitamin E and melatonin, respectively.


Both vitamin E and melatonin protect the retina against LPO in a dose-dependent manner. Although the IC50 value for melatonin is approximately 7.2 times higher than that of vitamin E, the pharmacological and physiological role of melatonin in the treatment and/or prevention of retinal diseases in vivo merits further investigation.


Siu AW et al. The efficacy of vitamin E and melatonin as antioxidants against lipid peroxidation in rat retinal homogenates. J Pineal Res 24(4): 239-44. May 1998.

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