In vitro antioxidant activity of Moringa oleifera lam. Leaf after Monascus purpureus fermentation and chemical component changes by untargeted metabolomics

This study aims to explore the enhancement effect of semi-solid fermentation of Monascus purpureus on the antioxidant properties of Moringa oleifera Lam. leaf (MOLL), as well as to analyze the potential antioxidant substances and their production mechanisms. In this study, the antioxidant activity of MOLL fermented with Monascus purpureus was evaluated in vitro. To gain further insight, we employed untargeted metabolomics to analyze the differentially abundant metabolites, and 30 key differentially expressed metabolites were identified. Notably, 15 of these metabolites were positively correlated with free radical scavenging activity. By utilizing a combination of KEGG topological and enrichment analyses, tryptophan metabolism was identified as a crucial pathway. Interestingly, Monascus purpureus fermentation significantly enhanced the conversion of tryptophan into metabolites with antioxidant properties, such as melatonin, kynurenine, and 3-hydroxyanthranilic acid, suggesting that fermentation with Monascus purpureus is a promising approach for enhancing the antioxidant properties of MOLL. •Fermentation enhances the antioxidant activities of MOL in vitro.•Fifteen potential markers are related to FMOL antioxidant activities.•The key metabolic pathway of FMOL is Tryptophan metabolism.•Tryptophan transform into antioxidant activity compounds in FMOL.