Targeted profiling and relative quantification of benzoyl diterpene alkaloids in Aconitum roots by using LC-MS/MS with precursor ion scan

Abstract

Benzoyl aconite alkaloids have myocardial protective effects at a low dose and produce toxic effects at high dose. Due to lack of enough reference compounds, most of the benzoyl alkaloids had few concerns, except the typical ones, i.e. aconitine, mesaconitine, and hypaconitine. To rapidly screen out and quantify benzoyl alkaloids, a high performance liquid chromatography combined with tandem mass spectrometry was proposed based on precursor ion scanning mode. First, a diagnostic ion at m/z 105 corresponding to benzoyl group was observed by using tandem mass spectrometry, which could be used for the rapid identification of benzoyl alkaloids. The targeted screening of these alkaloids was then conducted by using precursor ion scan of characteristic ion at m/z 105. Shengfuzi (the lateral root of A. carmichaelii) was taken as example, and 24 benzoyl-containing alkaloids were identified. The six major alkaloids including aconitine, mesaconitine, hypaconitine, benzoylaconine, benzoylmesaconine, and benzoylhypaconine were determined in the precursor ion scan mode by the standard curve method. Reliable linearity, sensitivity, precision, accuracy, and repeatability were obtained and validated. Then the relative response factors between these six analytes were calculated, which were not more than two times using any alkaloid as reference. Thus, the other 18 alkaloids lacking reference compounds were relatively quantified. This approach provides a useful tool for rapid identification and quantitative analysis of toxic benzoyl alkaloids, and also an efficient method for the safety assessment of Aconitum roots.

Keywords: Aconitum roots; benzoyl diterpene alkaloids; liquid chromatography with mass spectrometry; precursor ion scan; relative quantitation.