Complete 1H and 13C NMR assignment and 31P NMR determination of pentacyclic triterpenic acids

In this study we report the complete and unambiguous 1H and 13C NMR assignment of betulinic, maslinic, oleanolic and ursolic acids by utilizing high-resolution multidimensional NMR spectroscopy. In addition, we developed a 31P NMR methodology for the qualitative and quantitative analysis of these triterpenic acids. The 31P NMR methodology was validated using standard solutions of model compounds and has excellent accuracy and repeatability. NMR spectroscopy was proved to be a powerful tool for the determination of these bioactive molecules and will be an important aid for scientists who will perform interaction studies with these compounds, as well as researchers who need to determine and quantify them at their native sources.