Biologically active compounds from white and black mustard grains: An optimization study for recovery and identification of phenolic antioxidants

This work aimed to determine the best solvent mixture for extraction of antioxidant compounds from two varieties of mustard grains (white - Sinapsis alba and black - Brassica nigra) using a simplex centroid mixture design. For this, the experiments were performed using pure, binary or ternary solvent mixtures containing water, acetone and methanol. All extracts were analyzed for total phenolic compounds (TPC), DPPH- and ABTS-radical scavenging activities. The binary mixture of water and acetone, in equal proportions, was the best solvent combination to obtain an extract with higher TPC content and antioxidant properties. The extraction of antioxidant compounds with water/acetone resulted in increases of 23-folds for TPC, 48-folds for ABTS and 25-folds for DPPH compared to pure acetone. For black mustard, the extract obtained with this solvent combination was 19-, 31- and 27-folds higher than that produced with pure acetone for TPC, ABTS and DPPH, respectively. Additionally, the bioactive compounds from the mustard extracts were identified by UHPLC-MS/MS, as follows: 3,4-di-hydroxybenzoic acid, ferulic acid and sinapic acid in white mustard and 3,4-di-hydroxybenzoic acid, ferulic acid, sinapic acid and rutin in black mustard. This work reported for the first time an optimization study for recovery of phenolic compounds from mustard grains in order to obtain extracts with better antioxidant properties.