Isolation, identification, and quantum chemical analysis of structure-activity relationships of antioxidant peptides from sesame meal via Aspergillus niger fermentation and flavourzyme hydrolysis.

Sesame meal, a protein-rich by-product of oil processing, represents a promising source of bioactive peptides. An integrated fermentation-enzymatic strategy was developed to generate antioxidant peptides from sesame meal. Aspergillus niger fermentation enhanced by alkaline protease-derived soybean peptides improved proteolysis, followed by Flavourzyme hydrolysis under optimal conditions (pH 4.0, 50 °C, 20 h), yielding maximal antioxidant activity and peptide yield. All three in vitro antioxidant assays consistently demonstrated that peptides within 200 Da ∼ 2 kDa exhibited the strongest radical-scavenging capacity. Bioinformatics screening further identified 105 potential antioxidant peptides, from which six novel sequences were selected for detailed characterization. Quantum chemical calculations combined with in vitro validation revealed that the indole C of Trp, phenolic hydroxyl O of Tyr, and sulfur atom of Met are key reactive sites. Removal of these groups significantly reduced antioxidant activity. This study provides atomic-level insight into structure-activity relationships and supports the development of sesame meal-derived peptides as natural antioxidants.