( ...)Structural Determination of Flavonoids Using MSn

Jack Cunniff, Philip Tiller, Michael Harvey, and Adrian Land,
Thermo Finnigan

Natural Product Analysis

The data presented here can be acquired using the Thermo Finnigan LCQ Series of ion trap mass spectrometers.

Introduction

For more than five thousand years tea has been used in China as an herbal remedy. In recent years pharmacological studies have supported some of these health claims. Flavonoids, a class of polyphenolic compounds, found in tea, plants and many fruits have shown some promising results related to anti-cancer as well as antiinflammatory and anti-allergy properties. For these reasons, there has been renewed interest in both detecting and characterizing these compounds.

In many instances, flavonoids exist as their glycosylated conjugate. In a typical MS/MS experiment, glycosylated moieties may be cleaved from the molecular precursor with a resulting MS/MS spectrum which is difficult to relate back to a hypothetical structure. The primary reason for the difficulty is the fact that first generation fragment ions may undergo further fragmentation, which can result in a very complex spectrum. Third and fourth generation product ions can not readily be distinguished from second generation product ions.

The LCQ Series of mass spectrometers can perform MSn, so precursor ions are isolated before a subsequent MS/MS experiment is performed. Due to this isolation step, fragmentation spectra are generally less complex and ambiguous than traditional MS/MS spectra. Through successive MS/MS steps, product origins can be assigned. As the following experiments will show, the LCQ
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