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       Curcumin is the curcuminoid extracted from the dried rhizomes of Curcuma longa L. (C. domestica Valeton) (Family Zingiberaceae).
       It contains not less than 95.0 per cent w/w of C₂₁H₂₀O₆.

Description Orange-yellow needles.

Solubility Practically insoluble in water and soluble in alkalis.

Packaging and storage Curcumin shall be kept in well-closed containers, protected from light and stored at a temperature of –20°.

Identification The infrared absorption spectrum corresponds to the spectrum obtained from Curcumin RS (Fig. 1).

Melting temperature 179° to 183° (Appendix 4.3).

Assay Carry out the determination as described in the “Liquid Chromatography” (Appendix 3.5). (Note Filter Standard preparations (a), (b), Assay preparation and Mobile phases through a membrane having a 0.22-μm porosity or finer before subjecting into the chromatograph.)
       Standard stock preparation (a) A solution containing 400 μg of Curcumin RS per mL in acetonitrile.
       Standard stock preparation (b) A solution containing 400 μg of Curcuminoids RS per mL in acetonitrile.
       Standard preparation (a) Prepare a solution containing 40 μg of curcumin per mL by quantitatively diluting Standard stock preparation (a) with Mobile phase.
       Standard preparation (b) Prepare a solution containing 40 μg of Curcuminoids per mL by quantitatively diluting Standard stock preparation (b) with Mobile phase.
       Assay preparation Weigh accurately a suitable quantity of Curcumin, dissolve in and dilute with acetonitrile to obtain a solution containing 400 μg per mL of curcumin. Dilute this solution quantitatively with Mobile phase to have a solution of a known concentration of about 40 μg per mL of curcumin.
       Mobile Phase A 0.1 per cent v/v solution of formic acid and acetonitrile for chromatography (60:40).
       Chromatographic system
       DETECTOR Ultraviolet light (420 nm)
       COLUMN A stainless steel column (10 cm × 2.1 mm), packed with octadecylsilane chemically bonded to porous silica or ceramic microparticles (1.7 μm) (Waters-Acquity® or equivalent is suitable).
       COLUMN TEMPERATURE 40°
       FLOW RATE 0.5 mL per minute
       System suitability
       SAMPLE Standard preparation (a) and Standard preparation (b).
       SUITABILITY REQUIREMENTS The chromatogram of the standard preparation (b) is concordant with the reference chromatogram (Fig. 2). The approximate relative retention times of curcumin, desmethoxycurcumin and bisdesmethoxycurcumin are 1.00, 0.87 and 0.76 respectively, with reference to the curcumin peak.
       Column efficiency Not less than 5000 theoretical plates for the curcumin peak in the chromatogram of the standard preparation (a).
       Symmetry factor Not more than 1.5 for the curcumin peak in the chromatogram of the standard preparation (a).
       Resolution Not less than 2 between the curcumin and desmethoxycurcumin peaks in the chromatogram of the standard preparation (b).
       Relative standard deviation Not more than 2.0 per cent for curcumin in the chromatogram of the standard preparation (a).
       Procedure Separately inject equal volumes (about 2 μL) of Standard preparation (a) and Assay preparation into the chromatograph, record the chromatograms and measure the responses for the major peaks.
       Calculation Calculate the content of C₂₁H₂₀O₆ in the portion of the Curcumin taken, using the declared content of C₂₁H₂₀O₆ in Curcumin RS.