The roots of Onosma argentatum are used traditionally in Turkey for wound healing and bums. The n-hexane-dichloromethane extract of the roots, and four shikonin derivatives (deoxyshikonin, acetyl shikonin, 3-hydroxy-isovaleryl shikonin and 5,8-O-dimethyl acetyl shikonin) isolated from the n-hexane-dichloromethane extract were investigated for their ability to stimulate the growth of human amnion fibroblasts. A range of concentrations was studied and the extract found to stimulate the growth of human amnion fibroblasts in vitro at 0.1 mu g/mL whilst 5,8-O-dimethyl acetyl shikonin had the same effect at 0.05-5 mu g/mL, although cytotoxicity was observed at 50 mu g/mL for all samples. The extract and all the other isolated compounds showed cytotoxicity at 10 mu g/mL with the extract and 3-hydroxy-isovaleryl shikonin showing cytotoxicity at 5 mu g/mL. It is suggested that any wound healing effect of the roots of Onosma argentatum might be partly due to an additive effect of the shikonin derivatives present. (c) 2005 Elsevier Ireland Ltd. All rights reserved.