In the present study, the effects of process variables on alkaloids extraction were investigated first,
and the optimization of process variables was employed in accordance with box-behnken design (BBD) for maximal extraction of alkaloids from rhizome coptidis using response surface methodology. The effect of varied extraction time (1-8 h), solvent to sample ratio (20-60 mL/g) and acid concentration (0-1.0%) on alkaloids extraction were investigated. Best levels of variables were selected and set as central points in box-behnken design (BBD) for optimization.
    The optimal conditions for extraction of alkaloids from rhizome coptidis were phosphoric acid of 0.34%, extraction time of 5.002 h and solvent to sample ratio of 51.45 mL/g. Verification experiments were carried out and total alkaloid content of 207.1 mg BCE/g, berberine content of 72.48 mg BCE/g, and palmatine content of 15.77 mg PCE/g were obtained at the above mentioned predicted optimal conditions, which agreed well to the estimated maximal responses, suggesting that the RSM was successfully applied to the optimization of extraction of alkaloids from rhizome coptidis with low concentration phosphric acid solution