Possible role of radical intensity and oxidation potential for gallic acid-induced apoptosis

Gallic acid induced apoptotic cell death in human promyelocytic leukemia HL-60 cells. The effect of gallic acid was significantly reduced by blocking the free hydroxyl or carboxyl group with acetyl, methyl, ethyl, n-propyl or isoamyl group. This was paralleled with the decrease in the intensity of both gallate radical and oxidation potential. These data suggest the prooxidant action of gallic acid in the induction of apoptosis. On the other hand, the introduction of larger alkyl groups, such as lauryl or stearyl groups, to the carboxyl group of gallic acid, neither increased the radical intensity nor oxidation potential, but significantly increased its apoptosis-inducing activity. This suggests that the increase in the lipophilicity of the gallate molecule is an another factor which induces apoptosis by an as yet unidentified mechanism.