Production of amarogentin in root cultures of Swertia chirata.

Conventional and Agrobacterium rhizogenes-transformed root cultures were studied with respect to growth and amarogentin content following cultivation in various growth media. The fastest growth rate was observed using Nitsch medium. The best amarogentin content was obtained after cultivation in root culture (RC) medium for which the slowest growth rate was noticed. Addition of sucrose at 6% and 9% (w/v), respectively, also resulted in better growth rates and increased total but unaltered relative amarogentin content compared to 3% (w/v) sucrose. No change in amarogentin content was observed upon addition of elicitors, putative precursors of amarogentin biosynthesis, and plant growth hormones with the exception of salicylic acid and chitosan: at 100 mM salicylic acid a reduction and at 25 mg/L chitosan an increase of amarogentin were observed at significant levels. The cultivation of S. chirata roots in a 2-L stirred-tank bioreactor was successful only with a stainless-steel mesh fitted inside the culture vessel for immobilization of the roots. A 15-fold enhancement of amarogentin content in the medium was achieved by a root permeabilisation treatment using Tween 20 at 1.3% (v/v) final concentration in the bioreactor.