NMR based quantitation of cycloartane triterpenes in black cohosh extracts

The cycloartane triterpene content in the roots/rhizomes (RR) and aerial parts (PX) of Actaea racemosa (AR), A. podocarpa (AP), and A. cordifolia (AC) have been investigated by quantitative ¹H NMR (qHNMR). Thereby, it was demonstrated that qHNMR represents a powerful methodology for the analysis of crude plant extracts as it does not rely on the rarely available identical reference triterpenes. Specifically, the presence of the characteristic C-19 cyclopropane (exo/endo) hydrogen signals made it possible to quantify the less common/not ubiquitously present group of cycloartane triterpenes, directly in extracts. As an example, ARPX and ARRR were shown to contain, 3.8-20.8% ± 8.2% and 7.2-19.3% ± 4.0% of cycloartane triterpenes, respectively. The cycloartane concentration in ACPX and ACRR was 7.5-8.7% ± 0.8% and 13.9-28.5% ± 7.3%, respectively, based on the weight of the extract. AP was shown to contain notably lower amounts of the cycloartane triterpenes as compared to AR and AC in the roots/rhizomes. The content for APPX and APRR was only 2.1-3.3% ± 0.7% and 1.1-4.0% ± 1.5%, respectively. In addition, an example is presented for the identification of specific cycloartanes as marker compounds for AR within crude extracts based on the same qHNMR spectra and 2D NMR methods.