Sustainable recovery of phenolics from mustard seeds and study of their antioxidant and antimicrobial properties

This study aimed to investigate the effects of pH and temperature on the recovery of phenolic compounds from germinated and non-germinated mustard seeds. For this purpose, a Central Composite Rotatable Design (CCRD) was applied to mustard from two species (Brassica nigra and Sinapis alba). The evaluated responses included total phenolic content (TPC), antioxidant (ABTS, DPPH, FRAP) and antimicrobial activities, as well as phenolic identification and quantification by HPLC-DAD. The most suitable pH and temperature conditions for obtaining extracts with higher TPC content and antioxidant activity, varied according to sample type: for non-germinated white mustard (pH 5 at 37.5 °C); for germinated white mustard (pH 7.1 at 46.4 °C); for non-germinated black mustard (pH 5 at 25 °C) and for germinated black mustard (pH 8 at 37.5 °C). Under optimized conditions, sinapic acid was identified as the major phenolic compound in all samples, ranging from 700 µg g-1 (non-germinated white mustard) to 1270 µg g-1 (germinated black mustard). Furthermore, all mustard extracts inhibited microbial growth to varying degrees depending on the bacterial strain and sample evaluated. Overall, the results highlight the potential of green extraction using pH adjustment and mild temperatures for the recovery of phenolic antioxidants with antimicrobial activities.