ABSTRACT
To optimize the concentrate process of alkaloid from Leonurus japonicus by nanofiltration-ultrafiltration coupling technology with response surface methodology. The experiment showed that after ultrafiltration pre-treatment, the total protein removal rate was 94.38% in aqueous extract from L. japonicus, and the nanofiltration technology had obvious advantages over the conventional concentrate process. The optimal concentrate conditions were as follows：molecular weight cut-off 450, pH 3.07, concentration of stachydrine hydrochloride 80.15 mg•L⁻¹, and concentration of the total alkaloid 285.73 mg•L⁻¹. The cut-off rate was 93.37% and 95.85% respectively for stachydrine hydrochloride and the total alkaloid under the optimum conditions, with a relative error of 0.79% and 1.16% respectively. The combination of Box-Behnken design and response surface analysis can well optimize the concentrate process of L. japonicus by nanofiltration, and the results provide the basis for nanofiltration concentrate for heat-sensitive traditional Chinese medicine.