respectively (Table 2), which indicated a good agreement between the experimental and predicted values of the flavonoids yield. These results also suggested that the extraction yield was primarily determined by the linear and quadratic terms. Eq. (6) also showed that the linear effect was positive and quadratic effect was negative, and the coefficients of interaction were insignificant. Furthermore, the predicted results, according to the model for flavonoids yield, were close to the observed experimental responses, indicating that the generated models adequately explained the data variation and significantly represented the actual relationships between the reaction parameters.