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Introduction Pentacyclic triterpenoids (PCTs) are secondary plant metabolites. They are of exceptional interest as biologically active substances and raw materials for a wide range of medications. Thus, the development of a methodology for rapid screening of PCTs in plant biomass is an important task. Objective The goal of this work was to develop an approach for simultaneous screening and semi‐quantitative determination of PCTs in plant tissues by liquid chromatography–tandem mass spectrometry with a precursor ion scan (PrecIS). Materials and methods Pressurised liquid extraction (PLE) with methanol was used for the isolation of PCTs from plant biomass. Screening and semi‐quantitative determination of PCTs in the obtained extracts were carried out by reversed phase high‐performance liquid chromatography–tandem mass spectrometry in a PrecIS mode. Results The product ion at m/z 95 with collision energy of 40 V was used as a diagnostic ion to identify PCTs by the PrecIS mode. In plant materials, 26 PCTs and their derivatives, such as PCTs esters and glycosides, were detected and identified. Calculation of the relative response factor for nine available PCTs showed that using a betulin calibration curve allows us to estimate the semi‐quantitative content of PCTs and their derivatives in plant PLE extracts. Conclusion The developed approach can be applied for simultaneous untargeted screening and semi‐quantitative determination of PCTs and their derivatives in various plants at sub‐parts per million levels.

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Understanding the chemical structure of lignin in the plant phloem contributes to the systematics of lignins of various biological origins, as well as the development of plant biomass valorization. In this study, the structure of the lignin from birch phloem has been characterized using the combination of three analytical techniques, including 2D NMR, Py-GC/MS, and APPI-Orbitrap-HRMS. Due to the specifics of the phloem chemical composition, two lignin preparations were analyzed: a sample obtained as dioxane lignin (DL) by the Pepper’s method and DL obtained after preliminary alkaline hydrolysis of the phloem. The obtained results demonstrated that birch phloem lignin possesses a guaiacyl–syringyl (G-S) nature with a unit ratio of (S/G) 0.7–0.9 and a higher degree of condensation compared to xylem lignin. It was indicated that its macromolecules are constructed from β-aryl ethers followed by phenylcoumaran and resinol structures as well as terminal groups in the form of cinnamic aldehyde and dihydroconiferyl alcohol. The presence of fatty acids and flavonoids removed during alkaline treatment was established. Tandem mass spectrometry made it possible to demonstrate that the polyphenolic components are impurities and are not incorporated into the structure of lignin macromolecules. An important component of phloem lignin is lignin–carbohydrate complexes incorporating xylopyranose moieties.