Chemotaxonomy of Aster species from the Qinghai-Tibetan Plateau based on metabolomics

Introduction The genus Aster plants have been widely used for thousands of years in the Qinghai-Tibetan Plateau for the clearing of heat, detoxification, and the treatment of seasonal pandemic diseases. Although the presence of several flavonoid compounds in Aster has been reported by previous studies, the diversity of secondary metabolites within and among species is relatively unknown. Objective The metabolite profile of one Aster species was systematically compared with those of other taxa to find potential chemotaxonomic markers, delimit species, and assess chemodiversity. Method Samples of the above-ground parts of 11 Aster species were collected and their metabolites were analysed by ultra-high performance liquid chromatography with photodiode array detection and quadrupole time-of-flight tandem mass spectrometry. Unsupervised principal component analysis, supervised orthogonal partial least-squares discriminant analysis, heatmap analysis, and hierarchical cluster analysis were employed to analyse 95 representative samples from 11 Aster species and determine species-specific chemical markers based on a metabolomics database. Results Six phenolic acids and flavonoids were detected and quantified in all Aster species, suggesting that these compounds may be common constituents in the Aster genus. Metabolite analysis showed terpenoid compounds to be potential chemical markers for interspecies differentiation. Ent-kaurane-type diterpenoid glycosides were the main class of compounds in all Aster species except for A. farreri, which mainly contained oleanane-type pentacyclic triterpenoids. Diterpenoid glycosides were low-content chemotaxonomic markers and were detected for the first time in Aster species from the Qinghai-Tibetan Plateau. Conclusion Chemotaxonomy and metabolomics were used to support the phylogenic relationships of the Aster genus.