Characteristics of the primary reaction of hypocrellin A photosensitization.

The primary reaction of photosensitization of Hypocrellin A (HA) has been studied by using techniques of ESR, spin-trapping and spin-counteraction. The experiments show that HA is able to generate not only 1O2, but also O-2, .OH and HA- which are observed for the first time. The conversion of generating active oxygen into generating nonoxygen free radical is confirmed as well. Based on the characteristics of the primary reaction which generates these active substances (transient products), it is proposed that the photosensitized damage for the biological system by HA is probably related to not only 1O2 itself, but also a multiple effect from 1O2 as well as O-2, .OH and HA- free radical.