Free and insoluble-bound phenolics: How does the variation of these compounds affect the antioxidant properties of mustard grains during germination?

This work aimed to investigate how the variation of free and insoluble-bound phenolics affected the antioxidant properties of mustard grains from two varieties (black - Brassica nigra and white - Sinapsis alba) during different germination parameters. The germination conditions selected for each mustard variety to improve their antioxidant properties were different, as follows: (a) for white mustard - 72 h of germination at 25 °C in the dark and (b) for black mustard - 48 h of germination at 25 °C alternating dark and light periods. At these conditions, increases of 49, 72, 80, 68, 42, 66 and 45% were detected for total phenolic compounds (TPC), total flavonoids, condensed tannins, FRAP, DPPH, ABTS, and ORAC, respectively, for soluble extracts of white mustard compared to the non-germinated white mustard. The soluble extracts from black mustard, in turn, presented increases of 44, 18, 55, 29, 3, 160 and 42% for TPC, total flavonoids, condensed tannins, FRAP, DPPH, ABTS, and ORAC, respectively, compared to the non-germinated sample. Gallic acid, 3,4-di-hydroxybenzoic acid, sinapic acid, ferulic acid, coumaric acid, and rutin were identified by UPLC-MS/MS and were the main compounds detected in mustard extracts. Given the results obtained, germinated mustard grains have the potential for application as a functional and nutraceutical food.