Methodology for Pigments

Curcumin

The turmeric rhizome contains a variety of pigments. It is used as a natural dye in food industries and in cosmetic and pharmaceutical products as an antimicrobial


Principle
The powder contains a large number of aromatic compounds; curcumin is the major compound responsible for the characteristic color. In pure form it is an orange yellow crystalline powder, soluble in alcohol and glacial acetic acid. Curcumin content is used as an index for the quality of the produce. The method to extract curcumin is very simple and is given below.





Principle

Curcumin is quantitatively extracted by refluxing the material in alcohol and is estimated spectrometrically at 425nm.


Materials
» Absolute Alcohol
» Stoppered Flask and Air-condenser


Procedure
1.
Dissolve 0.2-0.5g of weighed, moisture-free turmeric powder in 250mL of absolute ethanol.
2.
Reflux the contents in the flask fitted with an air condenser over a heating mantle for 3-5h, compensate alcohol loss if any due to evaporation by adding alcohol freshly into the flask.
3.
Cool and decant the extract into a volumetric flask and make up the volume.
4.
Dilute a suitable aliquot (1-2mL) to 10mL with absolute alcohol. Measure the intensity of yellow color at 425nm in a spectrophotometer.


Calculation
Work out the curcumin content using the formula
Curcumin content g/100g =

0.0025 x A425 x volume made up x dilution factor x 100
0.42 x weight of the sample (g) x 1000

since 0.42 absorbance at 425nm = 0.0025g curcumin.


Notes
Alcohol is inflammable. Use no direct flame.