Due to the complexity and variation of the chemical constituents in authentic black cohosh (Actaea racemosa) and its potential adulterant species, an accurate and feasible method for black cohosh authentication is not easy. A high-resolution accurate mass (HRAM) LC-MS fingerprinting method combined with chemometric approach was employed to discover new marker compounds. Seven hydroxycinnamic acid amide (HCAA) glycosides are proposed as potential marker compounds for differentiation of black cohosh from related species, including two Asian species (A. foetida, A. dahurica) and two American species (A. pachypoda, A. podocarpa). These markers were putatively identified by comparing their mass spectral fragmentation behavior with those of their authentic aglycone compounds and phytochemistry reports. Two isomers of feruloyl methyldopamine 4-O-hexoside ([M + H]+ 506) and one feruloyl tyramine 4-O-hexoside ([M + H]+ 476) contributed significantly to the separation of Asian species in principle component analysis (PCA) score plot. The efficacy of the models built on four reasonable combinations of these markers in differentiating black cohosh and its adulterants were evaluated and validated by partial least-square discriminant analysis (PLS-DA). Two models based on these reduced dataset achieved 100% accuracy based on the current sample collection, including the model that used only three feruloyl dopamine-O-hexoside isomers ([M + H]+ 492) and one feruloyl dopamine-O-dihexoside ([M + H-hexosyl]+ at m/z 492). Graphical abstract Hydroxycinnamic acid amide glycosides are proposed as potential marker compounds for authentication of black cohosh.
Keywords: Hydroxycinnamic acid amide glycoside; Hydroxycinnamic acid ester; Nitrogen-containing; PCA; PLS-DA; UHPLC-HRMS.