ANALYSIS OF NAPHTHAQUINONE PIGMENTS IN SOME CHINESE MEDICINAL "ZICAO" ,ARNEBIA EUCHROMA

Six naphthaquinone pigments have been isolated from the root of Arnebia euchroma. They were identified as deoxyshikonin (Ⅰ), β, β-dimethylacrylalkannin (Ⅱ), acetylshikonin (Ⅲ), β-acetoxyisovalerylalkannin (Ⅳ), shikonin (Ⅴ) and β-hydroxyisovalerylalkannin (Ⅵ) based on spectral data (MS, IR, ¹HNMR), Compounds Ⅳ and Ⅵ were found for the first time from this plant.Five kinds of more widely used "Zicao", viz. Lithospermum erythrorhizon, Arnebia euehroma, A. guttata, Onosrma paniculatum and O. hookeri, were analysed by means of a quantitative HPTLC scanning method and found that the total contents of naphthaquinone pigments varied in accordance with species and localities of the species analysed, which ranged 0.39～1.80% in L. erythrorhizon, 2.13～6.73% in A. euehroma and 0.13～0.81% in A. guttata, O. paniculatum and O.hookeri. The result appeared to be parallel with the traditional criterion of qualification and evaluation.The present study revealed that all the above mentioned "Zicao" contained β, β-dimethylaerylalkannin and acetylshikonin as the main constituents and consequently they are phylogenetically closely related.