Application of different methods for measuring carotenoid status in maize grain

Abstract

Maize grain carotenoids are among the most abundant in cereals, exhibiting considerable diversity in the composition profiles. In this experiment, HPLC-DAD was used for lutein and zeaxanthin (predominant carotenoids) and β-carotene (proVA carotenoid) determination in flour of whole maize kernel. In addition, Raman spectroscopy, as a non-destructive method for pretreatment-free and rapid in situ screening of carotenoids status in different kernel regions, was applied. Six yellow maize inbred lines (L1-L6) were evaluated. After the spectral normalization, deconvolution was performed on three individual bands in three observed regions on kernel longitudinal section (aleurone cell layer, floury and vitreous endosperm), for all genotypes. It was found that the mean fitted area and intensity of three main carotenoid bands were the highest at 1520 cm-1, medium at 1155 cm-1 and the lowest for the band at 1007 cm-1, as spectral features used to identify carotenoids and quantify relative carotenoid concentration. Both the highest values for mean band fitted area and intensity observed in the floury endosperm, and the lowest in the aleurone cell layer, were recorded in the same regions for all genotypes evaluated. L1 and L2 exhibited the highest values, while L3 and L4 exhibited the lowest values for the average and total band area. Significant and negative correlation between carotenoid content quantified by HPLC-DAD and bands area fit for vitreous endosperm region obtained by Raman spectroscopy (-0.847; p≤0.05), and between carotenoid content and total bands area (-0.898; p≤0.05) indicated the competition for carbon supplies reflected through increased starch reposition over carotenoids accumulation.