The hydrolysis reaction of saponins
1. Precipitation reaction
(1) with metal saltsreagentIn the precipitation reaction, the aqueous solution or dilute alcohol solution of saponins can precipitate with some metal salts such as lead salts, barium salts, copper salts, etc. The aqueous solution of acidic saponins is precipitated by adding ammonium sulfate, lead acetate or other neutral salts. The aqueous solution of neutral saponins needs to add basic salts such as basic lead acetate or hydroxide oxidation to generate precipitation. This property can be used for the extraction and separation of saponins.
(2) With the precipitation reaction of cholesterol, the aqueous solution of steroidal saponins can be precipitated with cholesterol to form molecular complexes that are insoluble in water. The generated molecular complexes can be refluxed in ether and decomposed. Cholesterol is soluble in ether, while saponins are insoluble. According to this, steroidal saponins can be separated from the extract. Triterpenoid saponins andcholesterolComplexes can also be formed, but they are very unstable. Steroidal saponins and triterpenoid saponins can be isolated by using this property.
2. Hydrolysis reaction
(1) Acid hydrolysis
Mild acid hydrolysis: dilute acid (0.02---0.05ml/L of hydrochloric acid or sulfuric acid) in an aqueous alcohol solution can be refluxed for a short time to hydrolyze the glycoside bonds of deoxysugar, because the glycoside bonds of 2-hydroxy sugars are not easy to break under this condition.
Violent acid hydrolysis: To break the glycoside bond of the 2-hydroxy sugar contained in saponins, it is necessary to hydrolyze under severe conditions, usually with 24ml/L hydrochloric acid or sulfuric acid, and sometimes heat and pressure. Due to the severe hydrolysis conditions, the generated saponins often undergo changes such as water, cyclization, double bond shift, substituent shift, and configuration transformation, so that they are not true saponins, but artificial suborganisms. To obtain native saponins, enzymatic hydrolysis or Smith degradation can be used.
(2) Enzymatic hydrolysis, the hydrolysis of enzymes has a certain specificity, and different enzymes act on glycoside bonds of different properties. Amyrosidase existing in the leaves of Radix Zihua can only remove 1 molecule of Radix A and Bglucose, generating digitoxin and hydroxydigitoxin in turn.
Snail enzyme is a mixed enzyme, which can hydrolyze almost all glycoside bonds, and can gradually hydrolyze the sugars in the cardioside molecule until the aglycones are obtained. The enzymatic hydrolysis of digitalin and digitalin is different from that of indigoside. The former has acetyl groups on the glycosyl group, which has great resistance to enzymatic action and is slow to hydrolyze, while the latter hydrolyzes quickly. Different types of aglycones have different degrees of difficulty in being hydrolyzed. For example, type B cardioside is easier to be hydrolyzed than type A cardioside.
