Flavonoids in Chinese Medicine Extraction
There are many kinds of flavonoids in traditional Chinese medicine, and their solubility varies greatly due to their different structures and states. Free glycosides are insoluble or insoluble in water, but soluble in watermethanolEthanol, ethyl acetate, ether and other organic solvents or dilute alkali solutions, some of which are planar molecules, such as flavonoids, flavonols, chalcone, etc., are closely arranged between molecules, with a large attractive force, and are difficult to dissolve in water; instead of planar molecules, such as dihydrogen derivatives, the intermolecular arrangement is looser, the attractive force is reduced, which is conducive to the entry of water molecules and is more soluble in water.
The more hydroxyl groups are introduced into flavonoids, the greater the solubility in water. After the hydroxyl groups are methylated or acetylated, the solubility in organic solvents is increased. After flavonoids are glycogenated, the solubility in organic solvents decreases, and correspondingly the solubility in water increases, and the longer the sugar chain, the greater the water solubility. In addition, the different binding positions of sugars also have a certain impact on the solubility of glycosides in water. Taking gossipetin as an example, the water solubility of 3-0-glucoside is greater than that of 7-0-glucoside.
Chinese medicine plantsHydrolytic enzymes that often contain hydrolyzed glycosides must be inactivated when extracting flavonoids. There are many ways to inactivate enzymes, such as extracting with boiling water or more than 70% ethanol, adding lime when extracting.
The extraction methods of flavonoids have developed rapidly in recent years, and many new ideas have been proposed, such as ultrafiltration, ultrasonic, and supercritical CO2 extraction.
