Shikonin derivatives from the roots of Onosma nigricaule (Boraginaceae)

Abstract

The genus Onosma (Boraginaceae) is represented by 87 species in Turkey [1]. The roots of some Onosma species are used for wound healing and burns [2,3] in Turkey. Onosma nigricaule is an endemic species for Turkey [1] and its roots are used for wound healing and burns in Erzurum Province. In this sudy, the roots of O. nigricaule (500g) were extracted with n-hexane:dichloromethane (1:1) (2L x 3) and then filtered. The filtrate was evaporated at 40°C. Three shikonin derivatives (deoxyshikonin (1), β,β-dimethylacryl shikonin (2), and acetyl shikonin (3)) were isolated from this extract by using several chromatographic methods. The structures of the pure compounds were elucidated by using 1H-NMR and 13C-NMR Spectroscopy, and ESI-MS.