Fermentation is a crucial technology to improve the nutritional and functional properties of food materials. In this study, edible grass was processed by spontaneous fermentation. Changes in physicochemical properties, metabolites, and antioxidant activity of edible grass were investigated by colorimetric method and chromatography mass spectrometry-based non-targeted metabolomics approach during fermentation. The highest total polyphenol and total flavonoid contents, and free radical scavenging abilities were observed on the 17th day of fermentation. The maximum activity of superoxide dismutase was maintained stable in the fermentation time range of 7–70 days. In total, 16 differential metabolites were identified with fermentation duration up to 124 days. Fermented edible grass exerted protection from H₂O₂-induced cytotoxicity on HepG2 cells, regulating by the reduction in reactive oxygen species level and the increase in antioxidant enzyme activities. Overall, this study confirms that fermented edible grass obtained by spontaneous fermentation presented favorable nutritional and functional quality, and is expected to be a kind of food with antioxidant function.

In this study, gas chromatography-mass spectrometry (GC-MS) based untargeted metabolomics was used to describe the changes of metabolites in edible grass with Lactobacillus plantarum (Lp) fermentation durations of 0 and 7 days, and subsequently to investigate the protective effect of fermented edible grass on acetaminophen-induced stress injury in HepG2 cells. Results showed that 53 differential metabolites were identified, including 31 significantly increased and 22 significantly decreased metabolites in fermented edible grass. Fermented edible grass protected HepG2 cells against acetaminophen-induced stress injury, which profited from the reduction in lactate dehydrogenase (LDH) and malondialdehyde (MDA) levels and the enhancement in superoxide dismutase (SOD) activity. Cell metabolomics analysis revealed that a total of 13 intracellular and 20 extracellular differential metabolites were detected. Fermented edible grass could regulate multiple cell metabolic pathways to exhibit protective effects on HepG2 cells. These findings provided theoretical guidance for the formation and regulation of bioactive metabolites in fermented edible grass and preliminarily confirmed the protective effects of fermented edible grass on drug-induced liver damage.

Rosa Roxburghii (RR), a traditional Chinese medicinal fruit, is rich in bioactive substances that make it a potential natural antioxidant resource. This research aimed to study the antioxidant properties of RR by in vitro experiments and through intracellular assessment in H₂O₂-induced HepG2 cells. A non-targeted metabolic analysis was conducted to indicate changes in intracellular and extracellular metabolites. Differential metabolites and metabolic pathways were explored using PCA, PLS-DA, and KEGG pathway analysis. The results showed that RR rich in bioactive substances exhibited a significant antioxidative property in vitro and intracellularly. This property may be achieved by scavenging free radicals, increasing the activity of catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and the levels of bicinchoninic acid (BCA) while reducing the reactive oxygen species (ROS) generation. This study identified 13 differential metabolites intracellularly and 7 extracellularly, among which the key differential metabolites included D-glucopyranose, D-mannose, fructose, citric acid, malic acid, cholesterol, and cholestenone. These key metabolites primarily regulated glucose-related metabolism, the citrate cycle, and the primary bile acid biosynthesis pathway in H₂O₂-induced HepG2 cells. These findings provide potential application evidence of RR in the development of natural resources for functional foods.

In this work, spontaneously fermented and inoculation-fermented Akebia trifoliata fruit Jiaosu (SFAJ/IFAJ) were compared. The key metabolites and antioxidant activities of SFAJ and IFAJ were tracked and tested during fermentation. The antioxidant effect of fermented Akebia trifoliata fruit and the underlying mechanisms were explored using network pharmacology for the prediction and verification of the molecular targets and pathways of the Akebia trifoliata fruit’s action against oxidative stress. Furthermore, the results were verified by molecular docking and then investigated, based on a HepG2 cell model. The results of correlation analysis and principal component analysis (PCA) showed that there were significant positive correlations between the phenols, flavonoids, and terpenoids in SFAJ and IFAJ and their antioxidant activities. Network pharmacology and molecular docking analysis disclosed the antioxidation mechanism at the molecular level. In addition, both SFAJ and IFAJ were effective at alleviating oxidative stress in HepG2 cells. In particular, IFAJ performed better than SFAJ in protecting cells with an intracellular reactive oxygen species (ROS) level of 99.96 ± 4.07 U/mg prot, superoxide dismutase (SOD) activity of 41.56 ± 0.06 U/mg prot, catalase (CAT) activity of 91.78 ± 3.85 U/mg prot, and glutathione peroxidase (GSH-Px) activity of 39.32 ± 2.75 mU/mg prot in the IFAJ group. Collectively, this study revealed the changes in bioactive metabolite contents and the in vitro antioxidant activity during fermentation and investigated the protectiveness of SFAJ and IFAJ against oxidative stress within HepG2 cells, promoting the study of the antioxidant efficacy of IFAJ, thereby providing valuable reference data for the optimization of its preparation and the development of relevant products with health benefits.