Photostability of curcumine, demethoxycurcumin, and bisdemethoxycurcumin in rhizomes of Curcuma longa / 中草药

ABSTRACT

Objective: To study the photostability of curcumin (Cur), demethoxycurcumin (DMCur), and bisdemethoxycurcumin (BDMCur) in the rhizomes of Curcuma longa, and to investigate the photochemical conversion product of BDMCur. Methods: The stock solution of the extracts from the rhizomes of C. longa was kept in brown volumetric flasks. Then the absorbances of Cur, DMCur, and BDMCur were determined by HPLC analysis, and the solutions were placed in the daylight or daylight/dark conditions for 0, 1, 2, 4, 6, and 8 h. The photochemical conversion products of BCMCur were detected by LC-MS analysis. Results: Both Cur and DMCur were stable in the daylight and daylight/dark conditions. BDMCur was liable to photochemical reaction in the daylight condition. Conclusion: Both Cur and DMCur have good photostabilities, but BDMCur is not stable in daylight condition. As a result, the sample solution of the rhizomes of C. longa should be conserved in dark.