Screening and semi‐quantitative determination of pentacyclic triterpenoids in plants by liquid chromatography–tandem mass spectrometry in precursor ion scan mode

Abstract

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.

Supercritical Fluid Chromatography—Tandem Mass Spectrometry for Rapid Quantification of Pentacyclic Triterpenoids in Plant Extracts

“…The outer layer of birch bark is dominated by betulin, erythrodiol, uvaol, betulinic and oleanolic acids (3.6–250 mg·g −1 ). The content of the components is consistent with the literature data [ 27 , 28 ].…”

“…This demonstrates that the analysis time (7 min) is 2–3 times lower than those reported in the literature for reversed phase HPLC [ 27 ] or even SFC on polar sorbent [ 33 ] methods and is comparable to the value attained in our recent work using HPLC on a stationary phase with mixed retention mechanisms [ 28 ]. It is worth noting that SFC, unlike mixed mode HPLC, does not require complex and time-consuming method optimization procedures due to there being fewer parameters affecting the separation.…”

“…The reliability of the obtained LODs and LOQs was proved by the analysis of a model mixture of analytes with concentration close to the limit of quantitation ( Figure S2 ). The developed method demonstrated a high sensitivity comparable to that reported in previous works using HPLC-MS/MS (8.3–150 μg·L –1 ) [ 27 , 28 ], even exceeding it. The calibration dependences were linear (R 2 > 0.999) for all ten triterpenoids (from LOQ to the maximum used concentrations), spanning at least two orders of magnitude ( Table 2 ).…”

“…Mass spectrometry techniques, especially MALDI MS, have been successfully used for the rapid screening of triterpenoids in plant materials [ 24 ], while the quantitative analysis of PCTs requires chromatographic separation of analytes. High-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS) in multiple reaction monitoring (MRM) mode is widely used for PCT quantitative analysis [ 25 , 26 , 27 , 28 ]. The authors have found that it is preferable to use atmospheric pressure chemical ionization (APCI) with positive ion mode, whereas using electrospray ionization (ESI) causes a decrease in PCT ionization efficiency due to the low polarity of the analytes (except triterpenic acids in negative ion mode).…”

“…It requires gradient elution and long analysis time when using reversed stationary phases which, however, do not provide a good chromatographic resolution between similar compounds with the same monoisotopic mass in some critical pairs of PCTs, such as erythrodiol/uvaol, β-amyrin/α-amyrin, and oleanolic/ursolic acids. Using the stationary phase with cross-linked octadecyl groups (Nucleodur C18 Isis) with higher resolution towards positional isomers made it possible to separate nine PCTs in gradient elution mode in only 25 min and achieve the limits of quantitation (LOQ) in HPLC-MS/MS analysis in the range of 10–22 μg·L –1 [ 27 ]. Stationary phases with a mixed retention mechanism can be used to reduce analysis time and enhance selectivity.…”