Comprehensive profiling of phenolic compounds by HPLC-DAD-ESI-QTOF-MS/MS to reveal their location and form of presence in different sorghum grain genotypes.

In this study, comprehensive profiling of the phenolic compounds in sorghum grain was achieved by analysing the free and bound extracts of sorghum bran and kernel fractions from five Australian sorghum genotypes (1 white, 2 red, 1 brown and 1 black coloured), using HPLC-DAD-ESI-QTOF-MS/MS. A total of 110 phenolic compounds were annotated, out of which 56 were reported for the first time in sorghum grain. Compounds with matched authentic standards were quantified/semi-quantified. Multiple factor analysis (MFA) was performed and heatmaps generated, which provided direct visualisation of the distribution of individual phenolic compounds/subclasses between the sorghum samples. The results indicated that phenolic compounds were concentrated on the bran, and free and bound extracts had different phenolic composition. The phenolic compound/subclass profile varied greatly among sorghum genotypes. Brown sorghum genotype (IS131C) had the highest concentration of total phenolic contents, and the bran fraction of brown sorghum had the most abundant and diverse phenolic composition among all tested samples. This study provides the most comprehensive phenolic profile of Australian representative sorghum grains up to date.