Cerium dioxide (CeO₂) was pretreated with reduction and reoxidation under different conditions in order to elucidate the role of surface Ce⁴⁺ and oxygen vacancies in the catalytic activity for direct synthesis of dimethyl carbonate (DMC) from CO₂ and methanol. The corresponding catalysts were comprehensively characterized using N₂ physisorption, XRD, TEM, XPS, TPD, and CO₂-FTIR. The results indicated that reduction treatment promotes the conversion of Ce⁴⁺ to Ce³⁺ and improves the concentration of surface oxygen vacancies, while reoxidation treatment facilitates the conversion of Ce³⁺ to Ce⁴⁺ and decreases the concentration of surface oxygen vacancies. The catalytic activity was linear with the number of moderate acidic/basic sites. The surface Ce⁴⁺ rather than oxygen vacancies, as Lewis acid sites, promoted the adsorption of CO₂ and the formation of active bidentate carbonates. The number of moderate basic sites and the catalytic activity were positively correlated with the surface concentration of Ce⁴⁺ but negatively correlated with the surface concentration of oxygen vacancies. The surface Ce⁴⁺ and lattice oxygen were active Lewis acid and base sites respectively for CeO₂ catalyst, while surface oxygen vacancy and lattice oxygen were active Lewis acid and base sites, respectively, for metal-doped CeO₂ catalysts. This may result from the different natures of oxygen vacancies in CeO₂ and metal-doped CeO₂ catalysts.

D-tagatose, a monosaccharide as well as a dietary supplement, has been reported as having a wide range of applicability in the food industry, however, the prebiotic activity, anticonstipation effects, and related mechanisms are still unclear. In this study, using the loperamide-induced constipation Kunming mice as the animal model, the effects of d-tagatose for the prevention of constipation were evaluated by gastrointestinal transit experiment and defecation experiment. Furthermore, the underlying mechanism was clarified by evaluating the change of the biochemical indicators and analyzing 16S rRNA amplicon of gut microbiota among the different mice groups. The results showed that the gastrointestinal transit rate, fecal number, and weight in six hours were significantly enhanced after the administration of d-tagatose. In addition, d-tagatose significantly increased the serum levels of acetylcholine (Ach) and substance P (SP), whereas the serum levels of nitric oxide (NO) were significantly decreased. Moreover, the 16S rRNA sequencing analysis revealed that the changes in the gut microbiota caused by constipation were restored by d-tagatose treatment. In conclusion, this study indicated that the administration of d-tagatose as a dietary supplement can effectively prevent and relieve constipation in Kunming mice, and it is a promising prebiotic candidate with constipation-relieving properties.

The aim of this work was to evaluate the main nutrients and their antioxidant properties of a Chinese wild edible fruit, Passiflora foetida, collected from the ecoregion of Hainan province, China. The analytical results revealed that P. foetida fruits were rich in amino acids (1097 mg/100 g in total), minerals (595.75 mg/100 g in total), and unsaturated fatty acids (74.18 g/100 g in total fat). The lyophilized powder of edible portion contained the higher polyphenols content than the inedible portion powder. The UPLC-Q-TOF-MS^E analysis of the extractable and non-extractable phenolics indicated the presence of 65 compounds including 39 free phenolics, 14 insoluble-glycoside-phenolics, and 22 insoluble-ester-phenolics. In addition, the non-extractable phenolics obtained by alkali hydrolysis showed significant antioxidant activities by/through DPPH and ABTS radical scavenging. These findings of P. foetida fruits, for the first time, suggest that these polyphenol-rich fruits may have potential nutraceutical efficacies.

This study aimed to explore the anti-inflammatory and gut microbiota modulation potentials of flavonoid-rich fraction (PFF) extracted from Passiflora foetida fruits. The results showed that PFF markedly reduced the production of nitric oxide (NO), tumor necrosis factor α (TNF-α), and interleukin 6 (IL-6) in LPS-stimulated RAW 264.7 cells. Meanwhile, PFF treatment also effectively decreased the phosphorylation levels of MAPK, PI3K/Akt, and NF-κB signaling-pathway-related proteins (ERK, JNK, p38, Akt, and p65). Moreover, PFF had an impact on microbial composition and metabolites in a four-stage dynamic simulator of human gut microbiota (BFBL gut model). Specifically, PFF exhibited the growth-promoting ability of several beneficial bacteria, including Bifidobacterium, Enterococcus, Lactobacillus, and Roseburia, and short-chain fatty acid (SCFA) generation ability in gut microbiota. In addition, spectroscopic data revealed that PFF mainly contained five flavonoid compounds, which may be bioactive compounds with anti-inflammatory and gut microbiota modulation potentials. Therefore, PFF could be utilized as a natural anti-inflammatory agent or supplement to health products.