Commonly used curcumin extraction methods include: ethanol reflux method, percolation method, acid-base method, sodium salicylate method, enzymatic method, ultrasonic method, microwave extraction method and supercritical CO₂ method, etc.
When curcumin is usually extracted from raw materials such as turmeric, the obtained extract is a mixture of curcuminoids. In order to obtain a purer curcumin product, further purification is required. Methods for purifying curcumin generally include: organic solvent extraction, column chromatography (according to different stationary phases, it can be divided into: activated carbon column chromatography, activated clay column chromatography, silica gel column chromatography, polyamide adsorption method and macroporous resin method, etc.).
The solvent extraction method utilizes the fact that the substances to be extracted are in two mutually insoluble (or slightly soluble) solvents. Due to different solubilities or different distribution coefficients, the substances to be extracted move from one solvent to another. , after repeated extractions, until a large amount of active ingredients are extracted. The organic solvent extraction method is used to extract curcumin, which makes use of the different solubilities of certain organic solvents to curcumin, turmeric oil and other lipid substances and resinous impurities. By selecting the appropriate solvent extraction method, curcumin can be separated and purified.
Since curcumin, demethoxycurcumin, and bisdemethoxycurcumin have similar structures and properties, it is difficult to separate the three compounds. Generally, solvent extraction is first used to purify curcumin from the curcumin mixture, and then thin layer chromatography is used to separate the curcumin. Liquid chromatography and infrared spectroscopy are used to analyze and identify curcumin.