Epoxidation of some natural furocoumarins and furochromones using gamma-ray.

Epoxidation of imperatorin (1a) with m-chloroperbenzoic acid (mcpba) under the irradiation of gamma-ray gave a mixture of epoxide 3a and dioxofuran 4a. Whereas, alloimperatorin (1b) under the same condition obtained the epoxide 3b as a sole product. On the other hand, it was successfully epoxidized xanthotoxin (1c) with mcpba under the same condition as above. In addition, visnagin (2a) was epoxidized to give a mixture of epoxides 5a, 6a. While, khellin (2b) gave the epoxide 5b, no other products were observed.

Photosynthesis of furocoumarin- and furochromone-types potential intercalative alkylating and oxidizing agents of DNA through photooxidations using gamma-ray.

The photooxygenation of imperatorin (1a) under gamma-ray irradiation afforded the hydroperoxides 2a and 3a. Similarly, the photooxygenation of alloimperatorin (1b) gave the hydroperoxide (2b). Visnagin (1c) was also photooxygenated to give the hydroperoxide (2c) as sole product. On the other hand, the photooxygenation of khellin (1d) gave the endoperoxide (2d) as a sole product. The epoxidation of imperatorin (1a) using hydrogen peroxide under gamma-ray irradiation afforded the epoxide 5a. Similarly visnagin (1c) and khellin (1d) were epoxidized to give the epoxides 5c and 5d.

Photolysis and membrane lipid peroxidation of human erythrocytes by m-chloroperbenzoic acid.

The aim of the present work was to investigate the biological hazard of photooxidation products of m-chloroperbenzoic acid (mCPBA), as a novel photo-sensitizer, on lysis and membrane lipid peroxidation of human red blood cells (RBC). The photohemolysis activity of mCPBA oxidative products was concentration- and exposure time-dependent. Ten minutes photoexposure time and 100 micromol/L of mCPBA concentration were optimum to study the effect of generated superoxide (O2.-) and hydroxyl (.OH) radicals on RBC. The hemolytic effect of mCPBA was highly significantly inhibited by formate (as an .OH radical scavenger) compared with the partial inhibition effect of SOD-like Cu(II) complex (as O2.- radical Scavenger). The MDA value (an end product of membrane lipid peroxidation of RBC) induced by mCPBA was highly significantly decreased by formate. The generation of O2.- radicals by mCPBA was also confirmed by the partial hemolytic effect of phenazine methosulfate (PMS., O2.- radical generation). The data suggest the molecular mechanism of the oxygen radical species (O2.- and .OH through the photosensitization reaction of mCPBA and explain that hydroxyl radicals (.OH) play an active role in the photohemolysis process and peroxidation of membrane lipids of human erythrocytes.