Purity Determination of Three Curcuminoids Found in Ten Commercially Available Turmeric Dietary Supplements Using a Reverse Phase HPLC Method

Abstract

The main active component present in turmeric is curcumin and is subsequently responsible for some of its therapeuticeffects. Turmeric, however, contains two other active molecules, namely demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC). Collectively, these three molecules are known as curcuminoids. Commercially available dietary supplements vary in these components. In this study the curcuminoids were analyzed using a reverse phase ion-pairing HPLC method. UV detection was used to detect the three curcuminoids at a single wavelength of 430 nm. The validation of the method was carried to ICH guidelines. Good repeatability of the method was achieved at concentrations of curcumin, DMC and BDMC equivalent to 136, 148 and 162 μM, respectively, with R.S.D. values of 2.25, 1.93 and 1.64%, respectively. Similarly, good reproducibility and linearity of the method was obtained for curcumin, DMC and BDMC. On completion of the validation, 10 commercially available turmeric dietary supplements were analyzed for their curcuminoid content. Results showed two of the turmeric dietary supplements to contain near pure curcumin. The other supplements tested contained significant amounts of DMC and BDMC. Similarly, there was a significant increase in curcuminoid content between supplements that contained turmeric extract and those that contained raw turmeric. Interestingly, supplements containing turmeric extract contained a significantly higher proportion of curcumin compared to DMC and BDMC, reflected in the ratio of curcumin: DMC: BDMC.