Fig. 4.

HPLC analysis for the shikonin production of the hairy roots in ¹/₂B5 and M9 liquid nutrient media. a, b Physical appearance of ethanol-extracted samples from hairy roots and spent liquid medium. c Chromatogram of standard shikonins (1 shikonin; 2 AS, acetylshikonin; 3 IBS, isobutylshikonin; 4 DAS, β, β’-dimethylacrylshikonin; 5 IVS, isovalerylshikonin). d–f Chromatogram of different shikonins from transformed hairy root extracts. g–i Chromatogram of different shikonins from liquid medium extracts. 7 HIVS, β-hydroxyisovalerylshikonin (inferential); 8 propionylshikonin and deoxyshikonin (inferential); 6 and 9 unknown compounds