The effects of supercritical carbondioxide extraction was investigated to compare previously validated extraction methods on total alkannin yield with Alkanna tinctoria collected form Antalya, Turkey. A two-step process was used; extraction of alkannin derivatives with supercritical CO(2) followed by alkaline hydrolysis of alkannin derivatives. A Box-Behnken exprerimental design was used to evaluate the effect of three variables, pressure (50-350 bar), temperature (30-80 degrees C) and CO(2) flow (5-20 g min(-1)) at 1:30 ratio of alkanna root:CO(2) amount. Response surface analysis revealed that the data were adequately fitted to a second-order polynomial model with R(2) 0.9665 and the most effective variable was pressure (P <= 0.05). Optimum conditions were determined as 80 degrees C, 175 bar, 5 g min-1 CO(2) flow yielding the highest total alkannins (1.47%) which was higher than conventional hexane extraction (1.24%) providing a solvent-free alternative for industrial production. (C) 2011 Elsevier B.V. All rights reserved.