Abstract:

Microwave was applied to the extraction of total alkaloids from semen Strychni, the dry ripe seeds of Strychnos nuxvomica L. and the extraction process was optimized in this study. Firstly, single factor studies were conducted to investigate the effects of microwave power and irradiation time, ethanol concentration, liquid/solid ratio and pre-microwave irradiation soaking time on total alkaloids yield. Subsequently, central composition design and multiple nonlinear regression analysis were employed to establish a mathematical model describing total alkaloids yield as a function of the above extraction conditions. Finally, the pairwise interactive effects of these extraction conditions on total alkaloids yield were examined based on response surface and contour plots. The optimal extraction conditions were determined as follows: microwave power 240 W, extraction time 6.7 min, liquid/solid ratio 6:1, ethanol concentration 58.8%. An experimental strychnine yield of 18.97 mg/g and an experimental brucine yield of 9.46 mg/g were obtained under such conditions, which were substantially consistent with their respective theoretical counterparts.

Key words: Semen strychni, microwave-assisted extraction, total alkaloids, response surface methodology, response value