More than just heat: ambient ionization mass spectrometry for determination of the species of origin of processed commercial products—application to psychoactive pepper supplements†
The application of direct analysis in real time high resolution mass spectrometry (DART-HRMS) to the determination of the originating species of the plants from which processed commercially available plant-based products are derived is described. As a proof of principle, the method was employed for determination of the provenance of psychoactive pepper species, namely Piper methysticum (aka kava) and P. betle (aka betel). In addition to being of agricultural importance, these species are also of relevance in a forensics context. DART-HRMS spectra showed that extractions, heat treatment and other steps associated with the manufacture of these products result in significant differences in the mass spectral fingerprints observed. Nevertheless, the presence of key species-specific biomarkers such as kavalactones and chalcones in P. methysticum, and a variety of terpenes in P. betle, were retained. Chemometric processing by principal component analysis using a selection of feature masses that represented both compounds common to each of the species, and others that distinguished them, showed that the two Piper spp. could be readily identified, regardless of the manufacturing process used to create the product, with a leave-one-out cross validation result of 100%. Furthermore, unsupervised statistical analysis processing by hierarchical clustering not only enabled P. methysticum and P. betle products to be distinguished from one another, but also permitted further discrimination that was based on the processing method used to produce them. Advantages of the method over commonly used conventional protocols include minimal methods development; the capability of analyzing material in its native form without resorting to solvent extraction, derivatization or other sample preparation steps; speed; and the ability to detect and definitively identify biomarkers characteristic of a species. The method has wide applicability and is particularly useful for analysis of products from plants whose genes have not been mapped, and which, as a consequence, cannot be subjected to DNA analysis to determine the originating plant species.