LC-UV-HRMS dereplication of secondary metabolites from Brazilian Vernonieae (Asteraceae) species supported through in-house database

Vernonieae species are known to biosynthesize sesquiterpene lactones and flavonoids as their main secondary metabolites. Dereplication strategies in natural products research have been widely explored, with benefits highlighted in the identification of secondary metabolites using databases. In this study, the chemical composition of Brazilian Vernonieae species was investigated, aiming to provide more details about the major chemical similarities and differences between subtribes of Vernonieae. An in-house database was built, comprising 651 metabolites previously reported in the literature for Vernonieae. One hundred and ten Vernonieae species, belonging to 10 different subtribes, were analyzed, employing UHPLC-UV-HRMS. The compounds were identified based on their ultraviolet spectra and molecular masses calculated from accurate mass measurements; and supported through the in-house database. Additionally, the fragmentation patterns in the mass spectra were used for structural elucidation and to confirm the peaks assignments. Forty-nine metabolites were identified by this approach including eight hydroxycinnamic acid derivatives, 24 flavonoids and 17 sesquiterpene lactones. Thus, Brazilian Vernonieae species were characterized by the presence of hydroxycinnamic acid derivatives, flavones, flavonols, flavone C-glycosides, flavonol O-glycosides and sesquiterpene lactones, mainly glaucolides, hirsutinolides and furanoheliangolides. Hydroxycinnamic acid derivatives were identified in all the investigated subtribes and a great diversity of flavonoids was found especially in Lepidaploinae, Lychnophorinae, Piptocarphinae and Vernoniinae species. Species of subtribes Lepidaploinae and Vernoniinae exhibited glaucolide-type and hirsutinolide-type sesquiterpene lactones, while Lychnophorinae species showed goyazensolide-type and eremantholide-type sesquiterpene lactones. Moreover, subtribes Centratherinae and Pipocarphinae were characterized by the presence of goyazensolides while a chrestanolide was exclusively identified in Chrestinae and Elephantopinae species. Based on their differential distribution in the analyzed subtribes, this study demonstrated the chemotaxonomic significance of sesquiterpene lactones within the tribe Vernonieae. (C) 2018 Elsevier Ltd. All rights reserved.