A chemometric approach to the quality control of turmeric (Curcuma longa) by high performance liquid chromatography

Curcuminoids, are the principal natural yellow pigments found in the turmeric rhizomes (Curcuma longa L. Zingiberaceae). Among them, curcumin (C), demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC) represent the main chemical components responsible for the bioactivity [1]. The presence of a simple and precise method based on the curcuminoids content that can be used for the quality control of turmeric has not been developed. Therefore, in this study, we developed a method for the analysis of turmeric samples collected from Algeria (AC) and Egypt (EC) using HPLC technique. The methanol extracts of 30 samples were analyzed in triplicates on an RP-18 column using methanol: acetic acid: acetonitrile as a mobile phase and a photo diode array detector. The curcuminoids were characterized by co-chromatography and their relative peak areas were calculated. Different pattern recognition procedures, including principal component (PCA) and hierarchical cluster (HCA) analyses were applied using the matrix built on the relative peak areas of 90 chromatograms. The score plot of total curcuminoids showed that the samples were discriminated according to the different percentage of total curcuminoids and that the main discriminating marker was DMC. Interestingly, the samples were subsequently segregated according to their geographical location, where the total curcuminoids in the Egyptian samples ranged between 92 – 96%, whereas the Algerian samples ranged between 58 and 97%. In HCA, the resulting dendogram classified the samples into two main clusters, based on the location confirming the results of PCA. This study demonstrates that the combination of fingerprints and PCA may serve as an efficient and simple method for the quality control of tumeric rhizomes.

Fig. 1: PCA score plot of relative peak areas of total curcuminoids

References:

[1] Jayaprakasha GK, Jagan Mohan Rao L, Sakariah KK. Improved HPLC method for the determination of curcumin, demethoxycurcumin, and bisdemethoxycurcumin. J Agric Food Chem 2002; 50: 3668 – 3672