Comparative metabolomics of two Centaurium species displaying variable flower coloration phenotypes

Abstract

Species of the genus Centaurium (family Gentianaceae), well-known medicinal plants, threatened in the nature, are a rich source of bioactive compounds that are of great interest for the pharmaceutical and biotech industry. While the phytochemical characterization was investigated in detail in roots and leaves, nobody has so far tackled the question about the specialized metabolites composition in the centaury flowers. In this work, using untargeted metabolomics approach, we examined phytochemical differences in flowers of two centaury species, Centaurium pulchellum (Sw.) Druce and Centaurium tenuiflorum (Hoffmanns. & Link) Fritsch, both displaying variability in flowers coloration, which grades from white to pink. UHPLC-Orbitrap MS characterization of methanol extracts in a negative ionization mode resulted in the detection of 82 compounds in total. The identified compounds represented six structurally distinct groups: phenolic acid aglycones and glycosides; iridoid glycosides and derivatives; flavonoid glycosides and aglycones; xantone glucosides and aglycones; hydorxycinnamic acid amides and other compounds. All compounds found were identified by exact mass search of their deprotonated molecule [M – H]–, MS2, MS3 and MS4 fragmentation behavior, as well as by comparison with the available literature. Flavonoid and xantone glycosides and aglycones are the main classes of metabolites identified, and their content was strongly associated with the coloration of the flowers. However, a clear insight into the molecular mechanism underlying the centaury flower coloration is still lacking. Herein, the ultimate goal of our research is to comparatevely profile the changes in metabolome and transcriptome between pink and white centaury flowers in order to pinpoint key compounds and genes controlling the flower color formation.