EPR-spin trapping kinetic studies of superoxide radicals produced by pmotosensitized hypocrellin A, a photodynamic therapeutic agent

Kinetics of superoxide radicals generation by a photodynamic therapeutic agent, Hypocrellin A has been studied by EPR-spin trapping technique. The rate constant (k(g)) for superoxide radicals generation by Hypocrellin A was found to be 5.0 x 10^-3 s^-1. The first-order rate constant (k₁) and the half-life time (t_0.5) for DMPO-O₂^- decay were 2.86 x 10^-3 s^-1 and 242.3 s, respectively. It appears that oxyradicals, generated during the photodynamic process, may be associated with the treatment of various skin diseases by photodynamic therapy of Hypocrellin A.