Wild watermelon can accumulate citrulline, a type of amino acid, which is effective in eliminating highly oxidative reactive oxygen named hydroxyl radical. It has been demonstrated that the antioxidative activity of wild watermelon juice, i.e. eliminating hydroxyl radical to suppress oxidation of salicylic acid, exceeds that of citrulline per se. This finding implies that wild watermelon contains a substance that has antioxidative activity other than citrulline and warrants further investigation to clarify the unidentified substances.
Reactive oxygen species designate a family of substances with high oxidative pottential. These compounds are naturally produced by the body through normal activities such as breathing, food ingestion, and exercise. Reactive oxygen species play important roles in various physiological processes such as immune defense against bacteria and specific signal transduction pathways. However, excess reactive oxygen species production may accelerate aging, cause fatigue, and may be a contributing factor in lifestyle-related diseases. Among reactive oxygen species, hydroxyl radicals have a particularly high oxidative potential.