Abstract

The roots of Arnebia euchroma contain naphthoquinone red pigments, which have been used as colorant in food, cosmetics and as a dye for textile industries. Besides, these have medicinal and pharmaceutical properties too. Cell suspension culture serves as an alternative for secondary metabolite production. In this study, various growth factors such as inoculum build up process, phosphate source and in situ extraction methods were investigated on naphthoquinone pigment yield in A. euchroma cell suspension cultures. Effect of direct (solid to liquid) and in-direct (liquid to liquid) inoculum build up process was clearly evident, as direct inoculum registered 19.53% higher pigment yield than in-direct. Increased pigment yield was recorded in media having potassium phosphate sources (KH₂PO₄ and K₂HPO₄) rather than sodium (NaH₂PO₄) or ammonium (NH₄)H₂PO₄. In situ extraction resulted in significantly higher yield of naphthoquinone derivatives (637.15 mg L^-1) than control (369.38 mg L^-1), along with higher volumetric and specific productivities. The density of liquid paraffin also influenced the in situ extraction. HPLC chromatograms showed acetylshikonin as the major naphthoquinone derivative in the quantified fraction. The results of present investigation revealed that optimized growth factors have significantly enhanced the yield (up to 72%) of naphthoquinone pigments.

Key words: Boraginaceae, cell culture, inoculums, paraffin, pigment, shikonin.

Abbreviation

BAP, 6-Benzylaminopurine; IBA, indole-3-butyric acid; PHW, liquid paraffin heavy weight; PLW, liquid paraffin light weight; DI, direct inoculum; IDI, in-direct inoculums.