Supercritical carbon dioxide extraction was employed to extract flavonoids from Pueraria lobata. The optimal conditions for flavonoid extraction were determined by response surface methodology. Box-Behnken design was applied to evaluate the effects of three independent variables (pressure, temperature and co-solvent amount) on the flavonoid yield of P. lobata. Correlation analysis of the mathematical-regression model indicated that a quadratic polynomial model could be employed to optimise the supercritical carbon dioxide extraction of flavonoids. From response surface plots, pressure, temperature and co-solvent amount exhibited independent and interactive effects on the extraction of flavonoids. The optimal conditions to obtain the highest flavonoid yield of P. lobata were a pressure of 20.04MPa, a temperature of 50.24°C and a co-solvent amount of 181.24ml. Under these optimal conditions, the experimental values agreed with the predicted values, using analysis of variance, indicating a high goodness of fit of the model used and the success of response surface methodology for optimising supercritical carbon dioxide extraction of flavonoids from P. lobata.
Keywords: Flavonoid; Pueraria lobata; Response surface methodology; Supercritical fluid.
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