Profiles of phenolic compounds in modern and old common wheat varieties determined by liquid chromatography coupled with time-of-flight mass spectrometry

Abstract

The health-promoting properties of common wheat (Triticum aestivum L.) have been largely attributed to the presence of unique phytochemicals of whole grains. The aim of this study was to profile the phenolic content of 16 old and 6 modern Italian wheat varieties, cropped in the same location and growing season. High variability was observed among the investigated wheat genotypes, both in the free and bound phenolic extracts. The total polyphenol content ranged from 885.5 to 1715.9 μmol GAE/100 g of grain and, on average, the bound fraction contributed for 72.0% to the total phenolic content. As regards the flavonoid content, the free fraction ranged from 50.7 to 106.1 μmol CE/100 g of grain and the bound fraction from 78.3 to 148.9 μmol CE/100 g of grain. Moreover, the interpretation of the mass spectra allowed the characterization of 34 phenolic compounds (104 including isomer forms) belonging to the phenolic acid, flavonoid, coumarin, stilbene, proanthocyanidin and lignan chemical classes. HPLC-ESI-TOF-MS analysis highlighted remarkable differences in the phytochemical fingerprints of old and modern wheat varieties. Six ancient wheat genotypes (Bianco Nostrale, Frassineto, Gentil Rosso, Gentil Rosso Mutico, Marzuolo d'Aqui, Verna) showed phenolic profiles with a number of total compounds and isomer forms much higher than that identified in the modern cultivars. The present findings confirm that ancient wheat may represent a valuable source of biodiversity, especially as regards phenolic compounds. The investigated old wheat genotypes may be successfully used in breeding programs for developing bread wheat varieties with added value in terms of health-promoting phytochemicals.