Abstract:

A three-level Box-Behnken design, combined with canonical and ridge analyses, was employed to optimize some process parameters for the ultrasound-assisted extraction of polysaccharides from Radix Glycyrrhiza, one of the most valued traditional Chinese medicines. The most critical factors affecting the extraction of polysaccharides from Radix Glycyrrhiza, were determined to be ultrasound power, length of extraction and extraction temperature. Using multiple regression analysis, the Box-Behnken experimental results were fitted into two quadratic polynomial models describing Radix Glycyrrhiza ploysacchride yield or purity as a function of the 3 above-mentioned factors, with determination coefficients of 98.98% and 91.67%, respectively. The canonical analysis of the established models revealed that three eigenvalues had different signs, indicating a saddle stationary surface. The optimal conditions for the extraction of polysaccharides from Radix Glycyrrhiza were determined using the ridge analysis to be: extraction time, 64.5 min; extraction temperature, 64.6 ℃; and ultrasound power 580 W. Under these conditions, the predicted and experimental values of Radix Glycyrrhiza ploysacchride yield were 9.62% and 9.56%, and those of Radix Glycyrrhiza ploysacchride purity were 71.36% and 65.65%, respectively. The Radix Glycyrrhiza ploysacchride yield given by conventional waterbath extraction for 1 h at 65 ℃ was only the first three of that given by optimized ultrasoundassisted extraction for 1 h at the same extraction temperature. According to infrared spectrometric analysis, the structure of Radix Glycyrrhiza polysaccharides obtained by the two methods were basically identical.

Key words: Radix Glycyrrhiza, polysaccharides, ultrasound-assisted extraction, response surface analysis, ridge analysis, infrared spectrometric