Improved isolation procedure for shikonin from the root of the Chinese medicinal plant Lithospermum erythrorhizon and its solubilization with cyclodextrins

•An improved isolation procedure for shikonin preparation from the dried root of Lithospermum erythrorhizon has been developed.•Shikonin could be solubilized with sulfobutylether-β-cyclodextrin.•The complex showed higher apoptotic activity than that of free shikonin against murine primary peritoneal macrophages.

In this study, we improved the method for the isolation and purification of the bioactive compound shikonin from the dried root of the traditional Chinese medicinal plant Lithospermum erythrorhizon without a tedious chromatographic separation. Furthermore, we also attempted the solubilization of shikonin in water with cyclodextrins (CDs) using a solid phase “high-speed vibration milling”. Among the various CDs, sulfobutylether-β-CD (SBEβ-CD) showed a highest solubilizing ability and 52.5% of shikonin was solubilized with equimolar amount of SBEβ-CD. In addition, the SBEβ-CD·shikonin complex showed higher apoptogenic activity than that of the same concentration of free shikonin against murine primary peritoneal macrophages. These results indicate that SBEβ-CD is a suitable excipient for clinical application of shikonin.