High resolution ultra high pressure liquid chromatography~time-of-flight mass spectrometry dereplication strategy for the metabolite profiling of Brazilian Lippia species

Plants belonging to the <i>Lippia</i> genus have been widely used in ethnobotany throughout South and Central America and in tropical Africa as foods, medicines, sweeteners and in beverage flavouring. Various taxonomic problems involving some genera from Verbenaceae, including <i>Lippia</i>, have been reported. In this study, the metabolite profiling of fifteen extracts of various organs of six <i>Lippia</i> species was performed and compared using UHPLC–PDA-TOF-MS. Fourteen phenolic compounds that were previously isolated from <i>L. salviaefolia</i> Cham. and <i>L. lupulina</i> Cham. were used as references. The annotation of the remaining LC peaks was based on concomitant online high mass accuracy measurements and subsequent molecular formula assignments following these different steps: (i) elimination of non-coherent putative molecular formulae by heuristic filtering, (ii) verification of the occurrence of remaining molecular formulae in databases, (iii) cross search with reported compounds in the <i>Lippia</i> genus, (iv) match with reported UV spectra, (v) estimation of the chromatographic retention behaviour based on the log <i>P</i> parameter of reference compounds. This strategy is generic and time-saving, avoids isolation/purification procedures, enables an efficient LC peak annotation of most of the studied compounds and is well adapted for plant chemotaxonomic studies. Within this study, the interconversion of four flavanone glucoside isomers was additionally highlighted by analytical HPLC isolation and immediate analysis using fast UHPLC gradients. Dereplication results and hierarchical data analysis demonstrated that <i>L. salviaefolia, L. balansae, L. velutina</i> and <i>L. sidoides</i> displayed significant chemical similarities, while the compositions of <i>L. lasiocalicyna</i> and <i>L. lupulina</i> differed substantially.