Structural classification of Quillaja saponins by electrospray ionisation ion trap multiple-stage mass spectrometry in combination with multivariate analysis

摘要

This thesis describes methods for structural classification of Quillaja saponins with electrospray ionisation ion trap multiple-stage mass spectrometry, in combination with multivariate analysis. The mass spectrometry method was optimised by the use of design of experiments. 47 of previously reported Quillaja saponins from the chromatographic fractions QH-A, QH-B, and QH-C have been investigated. MS1-MS3 spectra were analysed by multivariate methods such as PCA and PLS-DA. Fragmentation of saponins generally results in loss of end elements from the precursor ion. The essential part of this method is the re-referencing of spectra. Peaks in the obtained re-referenced spectra have a correlation to loss of common structural elements. The multivariate methods captured the variance corresponding to the common structural elements. Thus, the obtained models have the ability to predict new compounds that share the common structural elements. Two saponins previously not characterised were isolated and analysed by ESI-IT-MSn, the multivariate models predicted the structure. The obtained models were applied to HPLC on-line coupled MSn data and a rapid method for screening of saponin fractions was developed.