Optimization of ethanol–water extraction of lignans from flaxseed

The optimal conditions for the extraction of lignans from flaxseed were determined. A second-order regression for rotation-orthogonal composite design was used to investigate the effects of three independent variables, namely ethanol concentration (%), extraction temperature (°C), and extraction time (h) on the response, the acquired ratio of lignans. The independent variables were coded at five levels and their actual values selected on the basis of results of single-factor experiment. The second-order regression for rotation-orthogonal composite design consisted of 23 experimental points and 9 replications at the central point. Data were analyzed using MATLAB software. The results indicated that acquired ratio of lignans might be beyond 8% at a probability of 95% in the range of ethanol concentration: 56.6–83.4%, extraction time: 26.7–27.9 h, extraction temperature: 38.7–40.1 °C. And the optimal extraction conditions were ethanol concentration of 70%, extraction time of 28 h and extraction temperature of 40 °C according to the analysis of response surface. In this condition, the experimental acquired ratio of lignans was 8.975% (w/w; lignans/defatted flaxseed powder), which is close to the predicted value (9.316%).