A novel strategy for rapid screening of the complex triterpene saponin mixture present in the methanolic extract of blackberry leaves (Rubus cv. Loch Ness) by UHPLC/QTOF-MS.

Triterpene saponins are important chemical constituents in blackberry leaves and have significant antimicrobial activity, among other healthful properties. In this study, a new UHPLC-MS method was optimized with outstanding efficiency for a non-targeted metabolic approach and comprehensive analysis of bioactive compounds in blackberry leaves (Rubus cv. Loch Ness). With minimum sample treatment, phenols and triterpene saponins, among others, were separated according to their elution times. Once separated, the major triterpene saponins were classified by their aglycone moieties and their structures tentatively identified based on their accurate mass spectra in positive and negative ESI mode. By the use of UHPLC coupled to a TOF, a high-resolution and accuracy mass analyzer, reliable molecular formulas of the detected compounds were predicted, and along with the generated MS spectra in full scan mode, allowed the tentative identification and classification of the most abundant triterpene saponins presented the samples analyzed. A rapid and comprehensive strategy to study the complex saponin profile is presented. Unlike other LC-MS/MS methods, the proposed method requires just one mass analyzer, and to our knowledge, this is the first systematic study on triterpene saponins in blackberry leaves.