NMR-based analytical methods for quantifying boswellic acids in extracts employed for producing food supplements: comparison of 13C-qNMR and 1H-NMR/PLS-R methods

The content of boswellic acids (BAs) in Boswellia serrata extracts employed for producing food supplements is often overestimated due to the use of conventional non-selective quantification methods. Here, the applicability of NMR spectroscopy for the quality control of B. serrata extracts was evaluated by employing different strategies: C-13-quantitative NMR (qNMR) and H-1-NMR coupled with chemometrics. The C-13-qNMR demonstrated high precision and accuracy, but long-lasting acquisition times. C-13-qNMR quantitative results were used to build a PLS-R model on the H-1-NMR spectra to generate a faster analytical method. The R-2 and the RMSE in prediction were 0.925 and 5.878 respectively, indicating good model performances, which can be improved by increasing the number of extracts. Moreover, the identification of 3 extracts out of 33 without any trace of BAs underlined the importance of proper controls of the starting material to produce BA-based food supplements.