Tracking the changes and bioaccessibility of phenolic compounds of sorghum grains (Sorghum bicolor (L.) Moench) upon germination and seedling growth by UHPLC-QTOF-MS/MS

Abstract

In this study, phenolic profile/content was analyzed by high-resolution untargeted metabolomics after short germination (72 h) and seedling growth (144 h), using three sorghum genotypes varying in tannin content (IS 29569, Macia and IS 30400). In vitro antioxidant capacity and phenolic bioaccessibility were determined by microplate-based and INFOGEST methods, respectively. A total of 58 % annotated compounds were found in all genotypes; and phenolic acids and flavonoids represent more than 80 % of sorghum total abundance. PCA analysis showed higher phenolic variability in germination times (72 %) than genotypes (51 %). Germination reduced total ion abundance (-7 %) and free:bound phenolic compounds ratio (2.4-1.1), but antioxidant capacity remained constant. These results indicate the cell matrix-phenolic decomplexation, with the free compounds were quickly consumed after radicle emergence. Germination increased phenolic bioaccessibility (mainly in oral phase) but reduces flavonoids contents in gastric/intestinal digestion steps. This work can stimulate seed germination as a viable option for sorghum-based foods development, with improved nutritional and bioactive properties.

Keywords: Antioxidant capacity; In vitro digestion; Polyphenols; Seed germination; Sorghum.