Ferulic acid fluorescence intensity profiles and concentration measured by HPLC in pigmented and non-pigmented cereals

Pigmented and non-pigmented cereals were examined by fluorescence microscopy and local concentrations and distribution of ferulic acid (FA) mapped by fluorescence intensity profiles. Hand dissected fractions (pericarp, aleurone layer and endosperm) were analysed separately, following microwave-assisted extraction, for FA concentration using high performance liquid chromatography (HPLC). Fluorescence intensity profiles showed that FA distribution varied across the grains and fluorescence intensity values were highest in the outer layers and lowest in the endosperm representing the concentration of the fluorophore. FA concentration in the bran and aleurone layers of pigmented cereals was significantly different (p < 0.05) from the non-pigmented cereals, although purple barley and yellow corn had the lowest and the highest FA concentration in both fractions. The endosperm fraction of all grains had the lowest amounts of FA. Similar trends were observed in FA concentration as determined by HPLC and fluorescence intensity values across the grain. Overall, positive and significant correlation (r = 0.421, p < 0.0001) was found between FA concentration and fluorescence intensity values. These findings suggest that fluorescence intensity profiles may be a promising approach for assessing FA distribution and concentrations in grain in situ.