Equivalently Quantitative Ion Strategy with Quaternary Ammonium Cation Derivatization for Highly Sensitive Quantification of Lanostane-Type Triterpene Acids without Standards by Ultrahigh-Performance Liquid Chromatography–Tandem Mass Spectrometry (UHPLC–MS/MS)

Lanostane-type triterpene acids are one of the main active components in Poria cocos, which have strong anticancer, immune regulation, antiaging, and anti-inflammation effects. However, low abundance, structure similarity, poor ionization efficiency, and especially the lack of adequate standards has hampered their accurate quantification. In this work, we develop an equivalently quantitative ion strategy with quaternary ammonium cation derivatization and established only one calibration curve for highly sensitive quantification of lanostane-type triterpene acids by ultrahigh-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) in the absence of standards. Quaternary ammonium derivatives of all the lanostane-type triterpene acids generate two specific fragment ions of m/z 130 and 170. Moreover, the signal intensity of the m/z 170 fragment is positively correlated with the concentration of all derivatives under the optimal MS parameters, so this fragment is chosen as the equivalently quantitative ion to easily quantify derivatived lanostane-type triterpene acids. The concentration of derivatives and the signal intensity of m/z 170 have a good linear relationship, with a correlation coefficient (r2) of >0.999, and the good accuracy, precision, and high recovery guaranteed the reliability of lanostane-type triterpene acid derivative quantification. This derivatization method enables accurate quantitation of a total of 53 and 19 lanostane-type triterpene acids in the Poria cocos extracts and MDCK cell bidirectional transport samples with a limit of quantitation (LOQ) of 0.1 nM, respectively. This method also could be applied to quantitatively analyze the derivatives of the carboxyl compounds that have the same core structure with small differences in substituents.