Distinction between Actaea racemosa and Its Adulterants Using Feruloyl Dopamine-O-Hexosides as Taxonomic Marker Compounds

Reviewed: Geng P, Harnly JM, Sun J, Zhang M, Chen P. Feruloyl dopamine-O-hexosides are efficient marker compounds as orthogonal validation for authentication of black cohosh (Actaea racemosa) – an UHPLC-HRAM-MS chemometrics study. Anal Bioanal Chem. 2017; 409(10):2591-2600.

Keywords: Actaea dahurica, Actaea foetida, Actaea pachypoda, Actaea podocarpa, Actaea racemosa, adulteration, black cohosh, feruloyl dopamine-O-hexosides, HPLC-MS

The issues regarding the identity of ingredients labeled to contain black cohosh (Actaea racemosa, Ranunculaceae) are well-known, and have been the discussed in a number of publications as part of the Botanical Adulterants Program.^1-3 The main concern is the sale of related Actaea species labeled as black cohosh in materials originating from Asia. Chemical analysis methods have mainly investigated the triterpene glycosides, the phenolic acids, and dihydrofurochromones as marker compounds to distinguish the species.

Ultra high-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-MS) fingerprints of 26 botanically authenticated reference materials (9 A. racemosa, 3 A. dahurica, 9 A. foetida, 2 A. pachypoda, and 3 A. podocarpa samples) and five commercial dietary supplements purchased from the internet in the United States were evaluated by principal component analysis (PCA). The PCA clearly separated black cohosh from the potential adulterants, yielding four distinct clusters (A. dahurica and A. foetida formed one cluster, while all the other species clustered separately). Nine chemical compounds were identified as being important for the separation into the clusters: the well-known phenolic acids cimicifugic acid A, B, E, and F, fukinolic acid, and four lesser known compounds with a feruloyl dopamine-O-hexoside or feruloyl tyramine-O-hexoside structure. The identity of the hexosides, and the location of the glycosylation could not be determined by mass spectrometry.

The nine chemical compounds were used to build a model which allows authenticating black cohosh and distinguishing it from its adulterants. All of the five commercial supplements were confirmed as black cohosh.

Comment: The use of the feruloyl dopamine-O-hexosides as markers to distinguish black cohosh from its adulterants is proposed as an additional test in support of other methods of authentication. It is not clear if the phenolic acids alone suffice to build a chemometric model that allows distinguishing the species. The investigation of additional markers may make it easier to verify the authenticity of commercial materials and is worth being considered in quality control laboratories as part of the identity determination. On the other hand, the equipment used in this study, in particular the high-resolution accurate mass spectrometer, is not often found in quality control laboratories of dietary supplement manufacturers. While positive ion mode mass spectrometry is ideal to detect low amounts of nitrogen-containing compounds, the ability to measure these markers using the more widely available HPLC-UV/Vis instruments should be investigated. However, this would require that reference standards to measure these compounds to be commercially available.