Quantification of natural products in herbal supplements: A combined NMR approach applied on goldenseal.

Authentication of natural products is of major relevance in the context of manufactured drugs or herbal supplements since such active products generate a lucrative market. The analytical method to identify and quantify valuable natural products is critical for quality control and product assignment of herbal supplements. In this framework, we propose to apply a recently developed quantitative 2D NMR approach called Q QUIPU (Quick QUantItative Perfected and pUre shifted) in combination with 1D 1H NMR capable to access the concentration of three major alkaloids, berberine, ß-hydrastine and canadine, in the root extract of goldenseal (Hydrastis canadensis), one of the 20 most popular herbal supplements used worldwide. We highlight the complementarity of 1D and 2D quantitative NMR to accurately assess the amount of alkaloids with different range of concentrations and stability within extracts. In particular, unstable natural products having non-overlapped signals like berberine could only be quantified by sensitive and fast 1D 1H, while overlapped signals of ß-hydrastine and low intense ones of canadine could only be quantified with the recent 2D Q QUIPU HSQC. Results obtained from this combined approach have led to a good accuracy (<10%) as compared with coupled UHPLC-MS/UV techniques. This quantitative NMR approach paves the way to numerous applications where the accurate quantification of targeted compounds in complex mixtures is required, for instance in agricultural, food and pharmaceuticals products.