Towards fruitful metabolomics: high throughput analyses of polyphenol composition in berries using direct infusion...

Tannin-enriched extracts from raspberry, cloudberry and strawberry were analysed by liquid chromatography-mass spectrometric (LC-MS) techniques. The raspberry and cloudberry extracts contained a similar mixture of identifiable ellagitannin components and ellagic acid. However, the strawberry extract contained a complex mixture of ellagitannin and proanthocyanidin components that could not be adequately resolved to allow identification of individual peaks. Nevertheless, the negative ESI-MS spectra obtained by direct infusion mass spectrometric (DIMS) analysis described the diversity of these samples. For example, the predominance of signals associated with Lambertianin C in cloudberry and Sanguiin H6 in raspberry tannin extracts could be discerned and the diversity of signals from procyanidin and propelargonidin oligomers could be identified in the strawberry extract. The dose response for the main ellagitannin-derived signals in the raspberry tannin sample revealed a saturation effect probably due to ion suppression effects in the ion trap spectrometer. Nevertheless, DIMS spectra of whole berry extracts described qualitative differences in ellagitannin-derived peaks in raspberry, cloudberry and strawberry samples. In addition, positive mode DIMS spectra illustrated qualitative differences in the anthocyanin composition of berries of progeny from a raspberry breeding population that had been previously analysed by LC-MS. This suggests that DIMS could be applied to rapidly assess differences in polyphenol content, especially in large sample sets such as the progeny from breeding programmes.