EVALUATION OF SUPEROXIDE ANION-RADICAL SCAVENGING ACTIVITY OF SHIKONIN BY ELECTRON-SPIN-RESONANCE

The scavenging activity of shikonin (SK) for superoxide anion radical (O-2(.-)) was evaluated by electron spin resonance (ESR) to clarify th e mechanism of the enhancing effect of SK on wound healing and its ant i-inflammatory effect. SK quenched O-2(.-) in a dose-dependent manner. Values for the O-2(.-) scavenging activity of SK were converted to va lues representing the equivalent activity of superoxide dismutase (SOD ) and were termed SOD-like activity values. SK exhibited potent O-2(.- ) quenching activity and its SOD-like activity was calculated to be ab out 920 U/mg. These results suggested that the O-2(.-) scavenging acti vity of SK played an important role in enhancing wound healing and in the anti-inflammatory effect of SK. No difference in O-2(.-) scavengin g activity was observed between SK and its optical isomer alkannin. SK was reduced to SK semiquinone radical by O-2(.-). The SK semiquinone radical may be responsible for the anti-tumor and anti-bacterial effec ts of SK. (C) 1998 Elsevier Science B.V. All rights reserved.