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Hypocrellin A (HA), a perylenequinone derivative, is an efficient phototherapeutic agent. When HA is incorporated into small unilamellar liposomes of egg phosphatidylcholine, it generates 1O2 as demonstrated by 9,10-diphenylanthracene (9,10-DPA) photobleaching and detection of nitroxide radicals with ESR. The 1O2 quantum yield measured is 0.80±0.02. On irradiation of oxygen-saturated solution of HA-liposomes, hydroxyl radical OH is detected using DMPO as the ESR spin trapping agent. Hydroxyl radical is derived from superoxide radical anion O2-. The electron transfer reaction is also studied in deaerated solution. The results suggest that the photodynamic action of HA in lipid membranes proceeds via both Type I and Type II reactions.
Hypocrellin A (HA), a perylenequinone derivative, is an efficient phototherapeutic agent. When HA is incorporated into small unilamellar liposomes of egg phosphatidylcholine, it generates 1O2 as demonstrated by 9,10-diphenylanthracene (9,10-DPA) photobleaching and detection of nitroxide radicals with ESR. The 1O2 quantum yield measured is 0.80 ± 0.02. On irradiation of oxygen-saturated solution of HA-liposomes, hydroxyl radical OH is detected using DMPO as the ESR spin trapping agent. Hydroxyl radical is derived from superoxide radical anion O2 The electron transfer reaction is also studied in deaerated solution. The results suggest that the photodynamic action of HA in lipid membranes went via both Type I and Type II reactions.