1、 Extraction of alkaloids

The extraction of alkaloids is closely related to the solubility of alkaloids. According to the technological process, it can be divided into solvent extraction method, distillation method and ion exchange method. According to the nature of alkaloids; Extraction of water-soluble and fat soluble alkaloids. According to the solvent used, it is divided into organic solvent extraction method, ethanol extraction method and acid water extraction method.

（1） Solvent extraction

A weakly polar organic solvent extraction

Common solvents include benzene, chloroform and dichloroethane. Because alkaloids often form salts with acids in plants, during extraction, the crude drug powder should be mixed or ground with less alkaline water (such as 10% ammonia, sodium carbonate, or lime aqueous solution) until it is wet, so that the alkaloids can be transformed into free state, and then soaked or percolated with an organic solvent equivalent to 10 times the crude drug amount. The alkaloids in the leaching solution should be diluted with acid water (such as 1% - 2% hydrochloric acid) Extract 3 to 5 times until the extract contains no alkaloids. Each time the amount of acid water is 1 / 10-2 / 5 of the amount of solvent. At this time, the alkaloid and acid form salt and dissolve in acid water. After the acid water is filtered, wash it with ether or chloroform for several times to remove some fat soluble impurities. Then add alkaline water for alkalization, extract the alkaline water with chloroform and other solvents for 3 ^ - 5 times,wash the extract with water for 1-2 times, dry it with anhydrous sodium carbonate or anhydrous sodium sulfate, and evaporate it to dry, Total alkaloids were obtained.

Emulsification often occurs when extracting with chloroform. For example, the acid water extract is alkalized with caustic soda, and the emulsification is more serious when extracting with chloroform. Therefore, violent shaking should be avoided during extraction. Especially during extraction, the emulsion layer is more likely to be produced when the concentration is higher, so only gently rotate the separating funnel during extraction, that is, layering. After 2-3 times of extraction, shake the separating funnel appropriately to make it completely extracted. If emulsification occurs, separate it separately first, and then continue to extract it. The separated emulsion layer can be broken by static, centrifugation or suction filtration.