A new approach to discriminate Rosmarinus officinalis L. plants with antioxidant activity, based on HPTLC fingerprint and targeted phenolic analysis combined with PCA

Abstract

A new combined “untargeted” and “targeted” metabolomics approach to investigate Rosmarinus officinalis L. plants was proposed by using the merging of high-performance thin-layer chromatography (HPTLC) assay and liquid chromatography mass spectrometry (LC–MS) with principal component analysis (PCA). Rapid fingerprints of Rosmarinus extracts were obtained and compared by using HPTLC technique; targeted compounds were identified and quantified by LC–MS/MS (MRM), while the antioxidant capacity of extracts was evaluated by methods based on the ability to scavenge radicals such as ABTS+* and DPPH*, since the metabolite expression is generally correlated with the biological activity. By HPTLC fingerprints, a rapid visual comparison of secondary metabolites in Rosmarinus samples from different places of collection was obtained and PCA was performed providing an overview of the capacity of the HPTLC variables to discriminate samples. HPTLC fingerprint assisted by PCA results a reliable untargeted approach for the discrimination and classification of different samples on the basis of their geographical area, from west to east of Sardinia. The ‘targeted’ approach was performed by developing LC–MS/MS (MRM) method allowing the identification and quantification of 12 compounds belonging to the family of flavonoids and phenolic acids. The combination of quantitative data with PCA allowed to discriminate La Maddalena Rosmarinus sample from others, in a correlated way with antioxidant activities results, showing values significantly higher. A positive Pearson correlation between antioxidant activity measured with DPPH and ABTS and total phenolic contents, finally confirmed that antioxidant activity depends on phenolic amounts.