Characterization of the antiradical activity of betalains from Beta vulgaris L. roots

Betalains (betacyanins and betaxanthins), the main pigments of red beet (Beta vulgaris) roots, showed an antiradical effect when measured by the destruction of the 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS) free radical generated by the horse-radish peroxidase/hydrogen peroxide-mediated oxidation of ABTS. The antiradical activity of betacyanins was greater than that of the betaxanthins and increased with the pH of the reaction medium. The different antiradical properties shown by both types of betalain is discussed in light of the respective ease with which it is possible to withdraw one electron from their molecules and the stability of their corresponding radicals. © 1998 John Wiley & Sons, Ltd.