1. Blois, M. S., Antioxidant determinations by the use of a stable free radical.Nature, 181, 1199–1200 (1958).
2. Chan, A. W. K. and Crow, W. D., Chemical constituents ofEriococcus confusus Maskell. I. The quinoid pigments.Aust. J. Chem., 19, 1701–1708 (1966).
3. Choi, J. S., Lee, J. H., Park, H. J., Kim, H. G., Young, H. S., and Mun, S. I., Screening for antioxidant activity of plants and marine algae and its active principles fromPrunus davidiana.Kor. J. Pharmacogn., 24(4), 299–303 (1993).
4. Cutler, R. C., Antioxidants, aging, and longevity, In “Free radicals in biology”, Pryor, W. A. (ed.), Academic Press, Orlando, Vol. 6, Chap. 11 (1984).
5. Danielsen, K., Aksnes, D. W. and Francis, G. W., NMR study of some anthraquinones from Rhubarb.Magn. Reson. Chem., 30, 359–363 (1992).