Ben‐Hur, E., New York Blood Center, 310 E. 67th Street, New York, New York, 10021, United States
Rosenthal, I., Department of Food Science, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan, 50250, Israel
Graziani, Y.G., Department of Life Science, Ben Gurion University, Beer Sheva, Israel

Abstract— Photohemolysis of erythrocytes in the presence of aluminum phthalocyanine tetrasulfonate as a sensitizer is inhibited by quercetin. D2O (98.5%) stimulated photohemolysis regardless of quercetin presence, suggesting the participation of singlet oxygen in the process. Since it has been shown that this flavonoid reacts with singlet oxygen, the protective effect might be attributed, at least partially, to its competitive reaction with singlet oxygen. At the molecular level, the alterations of membrane proteins that escort the process of photohemolysis, such as cross‐linking of spectrin monomers and of other membrane proteins, were selectively inhibited by quercetin. This effect was qualitatively similar to that induced by NaF, suggesting that quercetin may, like NaF, also inhibit type I photooxidations, which contribute to hemolysis. The lipophilicity of quercetin seems to be an essential factor in the inhibition process; rutin, a water‐soluble 3‐rutinoside of quercetin, had only a negligible protective effect on photohemolysis. Copyright © 1993, Wiley Blackwell. All rights reserved