Abstract: Response surface methodology was employed to optimize the extraction of alkaloid salt from lotus leaf based on one-factor-at-a-time experiments. The influences of extraction temperature, extraction time, solid-to-liquid ratio and phosphoric acid concentration on the extraction of alkaloid salt were studied. The results indicated the optimum conditions for alkaloid salt extraction were obtained as follows: temperature 92.7 ℃, extraction time 2.28 h, solid-to-liquid ratio 1:24.4(g/mL), and 0.27% (V/V) phosphoric acid as the extraction solvent. Under these conditions, and the experimental yield of alkaloid salt was 5.313 mg/g, which was in good agreement with the predicted yield of 5.372 mg/g with a relative error of 1.11%.

Key words: alkaloid salt, extraction yield, response surface analysis