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Curcumin is a diarylheptanoid obtained from the dried and fresh rhizomes of Curcuma longa.
It is the principal curcuminoid of turmeric and exists in several tautomeric forms, including a 1,3 -diketo form and two equivalent enol forms.
The 1,3-diketo form is more stable in water, while the enol form is more stable in the solid phase and in organic solvents.
Curcumin exhibits potent anti-inflammatory properties, which are also quite protective against some form of cancer progression.
Isolation Curcumin Method I
25gm of powdered dried turmeric rhizome is taken in a large beaker and mixed with 1000ml of distilled n-hexane using a magnetic stirring rod.
The resultant suspension is stirred for 3 days, then filtered and placed in a porous bag or ―thimble of strong filter paper placed in the chamber of Soxhlet apparatus.
310ml of methanol is heated in a flask, and its vapours are condensed in a condenser.
The condensed extractor drips into the thimble containing powdered turmeric rhizome and extracts it.
When the liquid level in the chamber rises to the top of the siphon tube, the liquid contents flood into the flask.
This process is continuously carried out till a drop of solvent from the siphon tube does not leave a residue when evaporated.
After 3 days, the solvent is evaporated in a rotary apparatus and then dissolved in 100ml of toluene.
The solution obtained is poured into a separatory funnel, added with 100ml 0.2M NaOH, and shaken for a few minutes.
The aqueous phase is collected and acidified to pH 3 using 0.2M HCl. The brown extract turns yellow as it undergoes clarification.
The filtrate is extracted with diethyl ether (3×100 ml).
In the final extraction, the ether turns pale yellow coloured indicating the end of extraction.
The combined ethereal phases are washed with 30ml water and dried over MgSO4.
Ether is removed completely under vacuum to leave a yellow coloured solid crude curcuminoid, which is purified by thin layer chromatography.
Identification test of Curcumin:
On treating the powdered drug with sulphuric acid, a crimson colour appears.
On treating the aqueous solution of turmeric with boric acid, a reddish-brown colour appears which turns greenish-blue on adding alkali.
On treating the powdered drug with acetic anhydride and concentrated sulphuric acid, a violet colour appears. A red fluorescence appears when this test is observed under UV light.
TLC Analysis:
The extracted curcumin can be analysed with thin layer chromatography.
Glass plates (20×20) coated with silica gel are used as the stationary phase.
Sample is applied on these plates at definite distance using standard borosilicate capillary.
These spots are allowed to dry.
Mixture of chloroform:ethanol:glacial acetic acid (94:5:1) is used as the mobile phase in the development chamber and allowed to saturate .
The prepared glass is placed in the development chamber for curcumin separation.
The amount of curcumin is measured with the aid of calibration curve of standard curcumin
Powdered drug of turmeric is extracted with alcohol in Soxhlet apparatus.
The obtained alcoholic extract is concentrated under reduced pressure and dried.
The other method also used for extraction of Curcumin form 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 out.
The separated mass will treat with petroleum ether and recrystallised from alcohol which will yield orange red needle crystals.
Melting point: Curcumin 183°C,
Desmethoxycurcumin 168°C and
Bisdesmethoxycurcumin 224°C
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