Phytochemical and Morphological Evidences for Shikonin Production by Plant Cell Cultures of Onosma sericeum Willd

Shoot regeneration, callus growth, and biosynthesis of shikonin in callus cultures of Onosma sericeum were examined. Plant tissue culture was used as an alternative method for increasing the production of shikonin, a secondary metabolite. The isolated cultures were subjected to abiotic factors such as light, plant growth regulators, and nutritional factors. Identification was carried out by High-Performance Liquid Chromatography (HPLC) after 10th subculture. Nodal explants were incubated in Murashige and Skoog (MS) medium along with different combination of growth hormones. Shoot regeneration from calli were achieved on MS basal medium supplemented with 3 mg/l 6-benzylaminopurine (BAP) and 0.5 mg/l Naphthalene acetic acid (NAA) under light cycle. Shikonin was formed in dark culture. Calli grown on MS (ammonium ion-free) medium supplemented with 3 mg/l BAP and 0.5 mg/l NAA contained the maximum shikonin level (15.26 mu g/mg DW). Minimum shikonin content (9.85 mu g/mg DW) was observed in calli cultured on MS (ammonium ion-free) medium supplemented with 3 mg/l BAP and 0.5 mg/l indole-3-acetic acid (IAA). In establishing cell culture, the ammonium ion, and light cycle inhibited shikonin formation. This is the first report on the establishment of isolated cultures of O. sericeum for shikonin production and callus growth.