Studies on in vitro metabolism of shikonin

Shikonin is one of the active components isolated from the root of Arnebia euchrona (Royle) Johnst. It has been shown to possess significant antibacterial, antiinflammatory and antitumour activities and has been used clinically. In this paper, rat liver microsomes were incubated in vitro to study the metabolism of shikonin and a reverse-phase high performance liquid chromatography/photodiode array detector (DAD) method was used to separate and detect the metabolites. The effects of several factors on the metabolism were investigated and the metabolic system was optimized. The main metabolites were purified by RP-HPLC and their structures were determined by UV, 1H-NMR and MS. S-1 was dihydroxylated shikonin, S-2 was 2-OH shikonin and S-3 was 6-OH or 7-OH shikonin.