Isolation of Curcumin: Curcumin or curcuminoids compounds are obtained from dried rhizomes of Curcuma longa belonging to the family Zingiberaceae. These compounds are diarylheptanoid compounds. Curcuminoids constitute about 50 to 60 percent of the mixture of three main curcuminoids named Curcumin, desmethoxycurcumin, and bisdemethoxycurcumin. Commercial Curcumin contains 97 percent pure product when it is isolated from Curcuma rhizomes.
The powdered drug of turmeric is extracted with alcohol in the Soxhlet apparatus. The obtained alcoholic extract is concentrated under reduced pressure and dried.
The other method was also used for the extraction of Curcumin from Curcuma. In this method, the powdered drug is extracted with hexane followed by acetone. The obtained acetone extract is concentrated and dried. This process will yield Curcumin. The most efficient method for Curcumin isolation is to extract the drug with hot ethanol. Then concentrate the filtrate and treat the concentrate with superior grade kerosene, a solid mass will separate. The separated mass will treat with petroleum ether and recrystallized from alcohol which will yield orange-red needle crystals.
Melting point: Curcumin 183°C, Desmethoxycurcumin 168°C and Bisdesmethoxycurcumin 224°C.
Thin-layer chromatography of Curcumin
1 mg of Curcumin is dissolved in 1 ml methanol and applied spots of silica gel G plates. Then elute the silica gel G plates in the solvent system chloroform-ethanol-glacial acetic acid in a ratio of 94:5:1. The eluted plate should be dried and visualized under 366nm light. Curcumin shows a bright yellow fluorescent spot at Rf value 0.79. The Rf value for desmethoxycurcumin is 0.60 and bisdesmethoxycurcumin is 0.43.
Identification Test of Curcumin
- The powdered drug turmeric is treated with acetic anhydride and concentrated sulphuric acid (a few drops) develops the violet colour of the solution. When this solution is observed under UV light shows intense red fluorescence which indicates the presence of Curcumin.
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