In a 250 mL three-necked flask, 60 mL of deionized water was added followed by 10 g of hydrated saponinamine. Under stirring conditions, the pH of the reaction system was adjusted to 1.5-3.5 by slow dropwise addition of 6 M hydrochloric acid solution. the reaction mixture was stirred continuously for 30 minutes. Appropriate amount of activated carbon was added and stirring was continued for 10 min before the activated carbon was removed by thermal filtration. The filtrate was concentrated to 1/3 of the original volume in a rotary evaporator. appropriate amount of isopropanol was added to the concentrate and cooled to 0-5 °C in an ice water bath to precipitate crystals. The crystalline solid was collected by filtration and washed with a small amount of cold isopropanol. The resulting solid was pre-dried in an oven at 30°C for 2 days and subsequently transferred to a glass desiccator fitted with silica gel desiccant and further dried at room temperature. Finally, the product was placed in a vacuum oven and dried under vacuum at 20 °C and 0.08 MPa for 6 h. 8.3 g of white to light yellow crystalline powder was obtained. Product identification: (1) About 10 mg of the product was dissolved in 5 mL of water and divided into two test tubes. Add 1 drop of bismuth potassium iodide solution to the first test tube and an orange-red precipitate was observed; add 1 drop of potassium iodide solution to the second test tube and a brown precipitate was observed. (2) About 10 mg of the product was dissolved in 5 mL of water, and 2 drops of ferric chloride solution and 1 drop of potassium ferricyanide test solution were added sequentially, and the solution appeared blue.
