Photohemolysis Sensitized by the Furocoumarin Derivative Alloimperatorin and its Hydroperoxide Photooxidation Product

The dark and photosensitized effects of alloimperatorin methyl ether 1 (hereafter simply alloimperatorin) and its photooxygenation product alloimperatorin hydroperoxide 2 were investigated on human erythrocytes. The results reveal that the furocoumarin 1 photosensitizes efficiently the hemolysis of erythrocytes. The rate of photohemolysis increases on raising the temperature of the postirradiated incubation from 4°C to 37°C. Thermal activation of the photohemolysis and inhibition by 2,6-di-tert-butyl-p-cresol (BHT) suggest that the furocoumarin 1 photosensitizes lipid peroxidation, increasing permeability in the erythrocyte membrane. The hydroperoxide 2 induces dark and photosensitized hemolysis more efficiently than the furocoumarin 1. The rate of hemolysis induced by 2 increases with the incubation temperature and decreases in the presence of tert-butanol and BHT. The hydroperoxide 2 photosensitizes the formation of lipid peroxidation products as shown by the reaction with thiobarbituric acid. This process is diminished by BHT. Our data imply that the photohemolysis sensitized by the furocoumarin 1 is caused by the in situ-formed photooxygenation product 2. Such hydroperoxides are potent hemolytic agents in the dark and especially on photosensitization.