Pure betalains and betalain-containing extracts have demonstrated a strong antioxidant activity. The activity determined is higher than that detected for other well-known compounds such as ascorbic acid, catechin, and Trolox. Glucosylation in betacyanins has been demonstrated to reduce the activity of pigments due to the blockage of one of the hydroxyl groups. However, the presence of these groups is not necessary to express the antioxidant activity, in contrast to other known antioxidants. Thus, an “intrinsic activity” exists in all betalains studied, which can be enhanced by the presence of hydroxyl groups.