Optimization of total alkannin yields of Alkanna tinctoria by using sub- and supercritical carbon dioxide extraction

Abstract

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 °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 °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.