Optimization of the Extraction of Total Alkaloids From Lotus Leaves by Acidic Ethanol and Its Purification by Macroporous Resins

ABSTRACT This acidic ethanol extraction method was adopted to extract total alkaloids from lotus leaves. Single‐factor experiments combined with response surface methodology (RSM) were employed to optimite extraction conditions. The optimal extraction parameters were determined as follows: 55 °C, 77% ethanol, 0.66% hydrochloric acid, under which the extraction yield of total alkaloids reached 4.14%. D101 macroporous resin was selected for the purification of crude alkaloid extracts. The resin exhibited an adsorption capacity of 8.60 mg/g and a desorption rate of 43.39%. The optimized purification conditions were as follows: 4 mg/mL sample solution, 50% ethanol eluent, 1.5 BV/h flow rate, 30 mL loading/100 mL elution volume. After purification, total alkaloid purity reached 89.31 ± 1.33%. Adsorption obeyed pseudo‐second‐order kinetics and Temkin isotherm, being spontaneous and endothermic. This provides improved methods for isolating bioactive alkaloids from lotus leaf.