The analysis of phenolic constituents in glabrous canaryseed groats

Abstract

Nineteen glabrous canaryseed samples, comprising brown- and yellow-coloured seeds, were investigated to determine the nature of phenolic constituents present. Total phenolic content (TPC) was determined, using the Folin–Ciocalteau assay. Flavonoid and phenolic acid compositions were determined, using high performance liquid chromatographic and mass spectrometric (LC–MS/MS) techniques. TPC ranged from 174 to 209mg/100g for canaryseed wholemeal samples. The canaryseed bran contained twice as much TPC as the wholemeal. The brown- and yellow-coloured whole canaryseeds exhibited the same flavonoid profiles. LC–MS/MS analysis showed that the canaryseed acetone extract was rich in flavonoid glycosides, with the bran being mainly composed of O-pentosyl isovitexin and the flour having a compound at m/z 468. No proanthocyanidins were detected in the 19 samples. Ferulic acid was the dominant phenolic acid, followed by caffeic and p-coumaric acids. The wholemeal obtained from the brown-coloured group had significantly higher contents of ferulic (>196mg/kg) and caffeic (>96mg/kg) acids in comparison to the yellow-coloured canaryseed group. The latter had ferulic and caffeic acids at levels less than 165 and 78mg/kg, respectively, with one exception which had relatively higher levels (190 and 94mg/kg). Whilst canaryseed flour contained significantly very low levels of ferulic acid (22–34mg/kg), the bran was enriched in ferulic (593–766mg/kg), caffeic (304–452mg/kg) and p-coumaric (119–142mg/kg) acids.