[The antiinflammatory activity of shikonin and its inhibitory effect on leukotriene B4 biosynthesis]

Shikonin is one of the active components isolated from the dry root of Arnebia euchroma (Royle) Johnst (AERJ). It has been shown to have anti inflammatory activity on formaldehyde induced paw swelling in rats. Preparations of AERJ has been used clinically in curing phlebitis and vascular purpura. In the present study, sc administered shikonin was shown to have significant inhibitory effects on ear edema induced by croton oil in mice and paw swelling induced by yeast in rats. In order to investigate the influence of shikonin on biosynthesis of LTB4 and 5-HETE, an in vitro leukocyte incubation system was adopted. The results showed that shikonin has fairly strong inhibitory effects on LTB4 and 5-HETE biosynthesis. Its effects and concentrations fit a positive relationship within the range of 10(-7)-10(-4) mol.L-1. The equations of inhibition (Y) versus concentration (X, LogC) obtained by linear regression were Y = 166 + 18.7X (r = 0.9319) for LTB4 and Y = 173 + 18.7X (r = 0.9856) for 5-HETE. The IC50 were 6.2 x 10(-7) and 2.6 x 10(-7) mol.L-1, respectively. The results also indicate that natural shikonin derivatives have similar inhibitory effects on LTB4 biosynthesis. These results suggest that inhibition of LTB4 and 5-HETE may play a major role in the mechanism of anti inflammatory effects of shikonin.