Characterisation and identification of isomeric dibenzocyclooctadiene lignans from Schisandra Chinensis by high-performance liquid chromatography combined with electrospray ionisation tandem mass spectrometry.

INTRODUCTION

Dibenzocyclooctadiene lignans are bioactive constituents in Schisandra chinensis (Turcz.) Baill. They are often present as isomers and this makes structural discrimination difficult.

OBJECTIVE

To develop a rapid approach towards the characterisation and identification of isomeric dibenzocyclooctadiene lignans from S. chinensis using HPLC-PAD-ESI-MS(n).

METHODOLOGY

The fragmentation behaviours of seven dibenzocyclooctadiene lignans from S. chinensis were studied using ion trap mass spectrometry with positive electrospray ionisation and loop injection. The fragmentation patterns of angeloylgomisin H, tigloylgomisin H, benzoylgomisin H and gomisin D were supported by high-resolution mass spectrometric analysis of some characteristic ions using a time-of-flight mass spectrometer. Combined with high-performance liquid chromatography and photodiode array detection, the established approach to the structural identification of dibenzocyclooctadiene lignans by ion trap mass spectrometry was applied to the analysis of extracts of S. chinensis.

RESULTS

According to the HPLC retention behaviour, the diagnostic UV spectra and the molecular structural information provided by multistage mass spectrometry spectra and the literature, a total of 25 dibenzocyclooctadiene lignans, including seven groups of lignan isomers, were identified or tentatively characterised in S. chinensis rapidly. One of these was reported as a constituent of S. chinensis for the first time.

CONCLUSION

This study has shown that HPLC-PAD-ESI-MS(n) may be used as an effective and rapid method for the characterisation and identification of isomeric dibenzocyclooctadiene lignans from S. chinensis.