Overview[1]
Carnosic acid A is a rare water-soluble and highly biologically active substance that currently only exists in Sage.
Preparation method[1]
A method for preparing carnosic acid A by hydrolyzing and converting salvianolic acid B, which is characterized by including the following process steps:
A. Base-catalyzed hydrolysis
Take 500g of salvianolic acid B solid, slowly add a 3% alkali aqueous solution to adjust the pH to 12, heat in a 55°C water bath for 30 minutes, wait until salvianolic acid B is hydrolyzed into gancicarnoic acid A, and then use the volume fraction 5% hydrochloric acid aqueous solution adjusts the pH of the hydrolyzate to weak acidity; slowly adding alkali aqueous solution can make the alkali solution evenly distributed, and the alkali-catalyzed hydrolysis of the system will be more complete.
HPLC detection can determine the hydrolysis of salvianolic acid B into gancicarnosic acid. When the pH value of the alkali solution is below 12, the reaction rate is very slow. When the pH value of the alkali solution is above 13, the reaction speed is too fast, which may easily lead to excessive hydrolysis and the target product cannot be obtained. After the reaction is completed, a weak acid needs to be adjusted to terminate the reaction, otherwise the hydrolysis will continue. During hydrolysis, the target substance is in a salt-forming state and needs to be reduced by adjusting the acid. Because the acidity of the hydrolyzate is weak, it is necessary to strengthen the acid during reduction, but the sulfuric acid reaction is too violent, so hydrochloric acid is chosen.
B. Extraction and concentration
Extract the hydrolyzate obtained in step A with ethyl acetate until the product is complete, concentrate at 45°C and drain the ethyl acetate phase.
C. Hydrolyzate purification
First dissolve the extraction concentrate with 25% acetonitrile, then filter it with a thin layer of silica gel, and finally filter it with a microporous membrane with a pore size of 0.45 μm, and then separate it on a high-efficiency preparative liquid chromatography column. The column filler is C18 filler and the mobile phase It is an acetonitrile aqueous solution with a volume fraction of 25%, the detection wavelength is 286nm, and the UV detector is online for monitoring, and the chromatographic peak section of the target compound is collected to prepare the solution.
In step C, methanol can also be used for dissolution, but considering that the mobile phase of acetonitrile is used during preparation, dissolution with the mobile phase is preferred.
The particle size of preparative chromatography column packing is generally 10-40μm. If the particle size is too small, the requirements for equipment will be higher, and the separation effect will not be ideal if the particle size is too small. Generally, the larger the diameter, the greater the flow rate.
D. Ganxi carnosic acid A recovery
Concentrate the qualified product segment at 45°C until there is no acetonitrile, extract it with ethyl acetate until the product is complete, concentrate and dry it at 45°C, and blast dry it at 45°C to obtain 50.23g of Ganxi carnosic acid A solid, which is analyzed by liquid chromatography The tested purity is 98.5%.
The calculated product yield is (50.23/500) × 100% = 10.05%.
Main reference materials
[1] [Chinese invention, Chinese invention authorization] CN201611257646.3 A method of hydrolyzing and converting salvianolic acid B to prepare glycyrrhizic acid A
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