Analytical strategies to determine the labelling accuracy and economically-motivated adulteration of natural dietary supplements in the marketplace: Turmeric case study

Turmeric has faced authenticity issues as instances of economic-adulterations to reduce the cost. We used carbon-14 and HPLC analyses as complementary methods to verify all-natural label claims of commercial dietary supplements containing turmeric ingredients. A high percentage of curcumin-to-curcuminoids value was used as an indicator to imply the presence of synthetic curcumin. However, using the HPLC method alone did not provide direct evidence of curcuminoids' natural origin, whereas using only the carbon-14 method cannot test for po-tency label claims and determine which constituent(s) contain C-14 radiocarbon. By analyzing results from both methods, a significant correlation between the percentage of curcumin-to-curcuminoids and % biobased carbon (Pearson's r =-0.875, p < 0.001) indicated that synthetic curcumin was greatly attributed to determined synthetic ingredients. Only four out of the 14 samples analyzed supported authentic label claims. This orthogonal testing strategy showed its potential for the quality control of turmeric products.

Automated summary

Turmeric has authenticity issues due to economic adulterations to reduce costs. Using carbon-14 and HPLC analyses as complementary methods, a significant correlation between the percentage of curcumin-to-curcuminoids and % biobased carbon was found, indicating synthetic curcumin greatly attributed to determined synthetic ingredients. Only four out of 14 samples supported authentic label claims, showing the potential of this testing strategy for quality control of turmeric products.