Chemistry and antioxidative activity of hot water extract of Japanese radish (daikon).

The comparison of antioxidative activity between the hot water extract and ambient water extract of Japanese radish (daikon) was carried out. The activity of the hot water extract was higher than that of the ambient water extract. One of the antioxidants was isolated as L-tryptophan that should no change in its amount that was determined between the hot water extract and ambient water extract. Moreover, tryptophan changed to 5-hydroxy tryptophan in the rat liver microsome model. This phenomenon may show that tryptophan is changed to another antioxidant in the body.