Metabolomics and chemometrics applied to the chemotaxonomy of the genus Aldama (Asteraceae) and classification according to geographical origin

The American genus Viguiera Kunth (Heliantheae: Asteraceae) was established in 1918 by Blake, and in 2011 the South American species were transferred to Aldama La Llave based on molecular analyses. However, the current taxonomic status of the Brazilian species requires revision. Classical phytochemical methods have been used for chemotaxonomic studies of Aldama [1 – 4], but modern methods were never applied. Thus, the aim of this work was to use untargeted metabolomics and chemometrics as a tool for the chemotaxonomic study of Brazilian Aldama, and for a classification according to their geographic origin. For metabolomics analysis, dried and powdered leaves of 25 species and three varieties were macerated (EtOH-H2O 7:3, 25 oC, 24h) and analyzed by UHPLC-HRFTMS. The LC-MS data (negative and positive modes) was processed, and chemometric analysis was based on Hierarchical Cluster Analysis (HCA) and Orthogonal-PLS (OPLS). Initially, the LC-MS data from the 28 Aldama was combined with data from other 50 Asteraceae species (different genera) and then analyzed by HCA. As a result, all Aldama were grouped in only one cluster, thus showing a robust chemical profile. Subsequently, six infrageneric groups of Blake's taxonomic classification were used as dependent variable to classify the Aldama species by OPLS. Some key secondary metabolites were found responsible for the discrimination of the species. Moreover, taxonomic classification of three new species could be suggested on the basis of their chemical profiles. Finally, the species were classified according to their geographical origin by OPLS. In summary, our metabolomic approach was applied successfully in chemotaxonomy and classification of geographical origin of Aldama.

Acknowledgements: CAPES, FAPESP (grants # 2010/51454 – 3 and 2012/10249 – 3) and CNPq.

Keywords: Aldama, Asteraceae, metabolomics, chemometrics, chemotaxonomy, geographical origin

References:

[1] Da Costa FB, Vichnewski W, Herz W. Constituents of Viguiera aspillioides and V. robusta. Biochem Syst Ecol 1996; 24: 585 – 587.

[2] Da Costa FB, Schorr K, Arakawa NS, Schilling EE, Spring O. Infraspecific variation in the chemistry of glandular trichomes of two Brazilian Viguiera species (Heliantheae; Asteraceae). J Braz Chem Soc 2001; 12: 403 – 407.

[3] Spring O, Zipper R, Conrad J, Vogler B, Da Costa FB. Sesquiterpene lactones from glandular trichomes of Viguiera radula (Heliantheae; Asteraceae). Phytochemistry 2003; 62: 1185 – 1189.

[4] Ambrosio SR, Schorr K, Da Costa FB. Terpenoids of Viguiera arenaria (Asteraceae). Biochem Syst Ecol 2004; 32: 221 – 224.