NMR based quantitation of cycloartane triterpenes in black cohosh extracts

Abstract

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.