Quality Evaluation of Turmeric Dietary Supplements in the United States Market Using a Quantification and UHPLC-HRMS Metabolite Ratio Approach

Turmeric is one of the most popular herbal botanicals used in the food and dietary supplement (DS) industries. As a DS, it faces labeling inconsistency and authenticity issues due to economic motivation. This research evaluated the labeling claim accuracy and chemical profile of commercial turmeric dietary supplemental products. Ten turmeric DSs from the US market along with one reference standard and two rhizome powders were analyzed using ultrahigh-performance liquid chromatography–high-resolution mass spectrometry. Except 2 samples not given clear label facts, only 3 out of the 10 samples analyzed met the labeling expectation of curcuminoid amounts based on the sum of curcumin (CUR), demethoxycurcumin (DMC), and bisdemethoxycurcumin (BMC) quantities. In addition, 13 known curcuminoids and volatile compounds were selected to represent the "natural" metabolite profile of turmeric, and the metabolite profiles of the commercial products were evaluated. Considering the addition of synthetic ingredients will break the "natural profile" ratio of turmeric, the ratios of curcuminoids/turmerones and ratios of CUR/DMC/BMC were selected as the quality markers after evaluating the metabolite profiles of turmeric rhizome samples and DSs. The natural turmeric (voucher sample and raw rhizome samples) has a ratio of less than 20% while some of the DS samples have ratios higher than 50% for turmerones/curcuminoids, and the curcumin ratio to curcuminoids is about 60 to 65% for the natural turmeric while some of the DS samples are well over 80%. The results suggest both the ratio of curcuminoids/turmerones and the ratio of CUR/DMC/BMC may be used as indicators for the quality markers of turmeric DSs.