Correlation between antiradical activity and stability of betanine from Beta vulgaris L roots under different pH, temperature and light conditions

When the antiradical activity and stability of betanine were studied at pH values of 3.5 and 8.5 and temperatures of 25, 50 and 75 degreesC, the results showed that the antiradical activity was greater at acidic pH and lower at higher temperatures, At basic pH the activity of betanine correlated well with its stability at the three temperatures assayed, suggesting that the degradation products, betalamic acid (BA) and cycle DOPA 5-O-beta -D-glucoside (CDG), did net contribute to this activity under the experimental conditions used. However, at acidic pH the degradation product, CDC;, did seem to contribute to the antiradical activity. Furthermore, at pH 3.5, betanine stability was so great that light conditions had no effect on the antiradical activity. At basic pH, too, light had no effect on betanine activity owing to the high instability of the pigment. (C) 2001 Society of Chemical Industry.