キラルカラムを用いたshikonin類の分析と、硬紫根、軟紫根におけるshikonin類の光学異性体比の特徴を利用した(R)-shikonin及び(S)-shikoninの効率的生産

概要

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"Koshikon" (the roots of Lithospermum erythrorhizon) and "Nanshikon" (the roots of Arnebia euchroma) have been used as natural dye and medicine. Interestingly, shikonins, the components of those species, exist as mixture of enantiomers. In this report, we isolated six shikonins from "Koshikon", and five shikonins from "Nanshikon", and determined the enantiomer ratios of them by chiral-HPLC analysis. From the "Koshikon", acetylshikonin and β-hydroxyisovalerylshikonin were obtained with the low R/S ratio (74/26 and 90/10), while isobutyrylshikonin, β,β-dimethylacrylshikonin, α-methyl-n-butyrylshikonin and isovalerylshikonin were obtained as almost pure R-form (>95%). On the other hand, the "Nanshikon" gave acetylshikonin with the low R/S ratio (34/64), and isobutyrylshikonin, β,β-dimethylacrylshikonin, α-methyl-n-butyrylshikonin and isovalerylshikonin as almost pure S-form (just about 100%). Generally, enantiopure shikonins have been obtained by hydrolysis of shikonin derivatives followed by several recrystallizations. We established an easy and efficient method for preparing enantiomerically pure (R)-shikonin and (S)-shikonin by removing low-enanntiopure acetylshikonin and β-hydroxyisovalerylshikonin from shikonins before the hydrolysis.
日本食品化学学会の論文
2014-04-25