and Melatonin Protect Against H202-Induced
in Rat Brain Homogenates by Tina J. P Frederiksen, Gitte Pless, Joaquin J. Garcia
& Russel J. Reiter
brain is particularly susceptible to free radical damage, and
it is therefore important to find agents that protect against
this process. The chief secretory product of the pineal gland,
melatonin, is a well known antioxidant. Pinoline is a recently
discovered compound with structural similarity to melatonin.
In the search for a new neuroprotective agent, the antioxidant
capacity of pinoline is compared to that of melatonin. Lipid
peroxidation was induced by adding H202
to rat brain homogenates. The degree of lipid peroxidation was
assessed by estimating the levels of thiobarbituric acid reactive
substances, malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA).
The antioxidant capacity of pinoline and melatonin was measured
as percent inhibition of lipid peroxidation in rat brain homogenates
after the addition of H202.
Both pinoline and melatonin were found to inhibit lipid peroxidation
in a dose-dependent manner. Under these in vitro conditions,
pinoline was found to be 7 times more effective than melatonin
in reducing MDA + 4-HDA levels, with an IC50
= 0.1 mM for pinoline and an IC50 = 0.7
mM for melatonin.