Three commonly used extracts of coumarin compounds
freeCoumarinMost of them are of low polarity. Generally, they can be extracted with solvents with low polarity. The solvent is recovered. The residue is cooled or placed in the refrigerator, and crystals will precipitate. Sometimes the residue is too viscous and the crystals are not easy to precipitate. You can add a small amount of solvent, or concentrate it to a small volume and put it in the refrigerator for crystallization. After combining with sugars to synthesize glycosides, it has higher polarity. Often a medicinal material contains a variety of coumarin components, which can generally be extracted with one solvent according to the method of increasing polarity. Currently commonly used extraction methods are as follows:
1. Solvent method
According to the type and polarity of coumarin, petroleum ether, benzene, ethyl ether, ethyl acetate, acetone and methanol are generally extracted in sequence. Due to the high toxicity of benzene, it should be used as little as possible or not. Free coumarin generally has low polarity. After extraction and concentration with a low polarity solvent, it can be directly crystallized or mixed in the refrigerator. The polarity of coumarin increases after glycoside formation. Use this method to extract and separate Qin Peel and other plants
2. Acid-base method
The separation is carried out by using the characteristics that coumarin lactones can be opened to form salts in case of alkali and can be restored after adding acid. Usually, the ether extraction solution is first extracted to remove the acidic components in an aqueous solution of sodium bicarbonate; then it is hydrolyzed in an aqueous solution or an alcohol solution of dilute and cold sodium hydroxide or potassium hydroxide. Coumarin is soluble in water due to salt formation, and then the neutral components that are not hydrolyzed are extracted with ether. After the alkali solution is neutralized with acid, the lactone component of coumarin is extracted with ether. The acid obtained after the saponification of other esters remains in the aqueous solution. This method is a classic method of large-scale production. Although it will produce some side reactions, it is still used today.
3. Supercritical fluid extraction method
The new technology of supercritical fluid extraction has been widely used in the extraction of coumarins. Free coumarins with small polarity can be extracted directly, while glycosides can be extracted by adding polar solvents such as ethanol as a clip. The extraction experiment of osthole with supercritical fluid has achieved good results.
