Quorum sensing effect of chiral d-glutamine on the modulation of the intestinal microbiota of mice by Lactiplantibacillus plantarum A3.

BACKGROUND: Amino acids (AAs) are the building blocks of proteins, but they also serve as biological compounds in biochemical processes, and d-AA isomers are increasingly being recognized as important signaling molecules. As the main organic substrate used by cells in the intestinal tract, the role of the chiral specificity of glutamine is still largely ignored. RESULTS: In a previous study, we found that d-glutamine affected the quorum sensing of Lactiplantibacillus plantarum A3, promoted the release of signaling molecule AI-2 and up-regulated the expression of the LuxS gene. The results showed that when d-glutamine and L. plantarum A3 were simultaneously applied to a mouse model, the diversity and abundance of intestinal flora in both male and female mice were increased. Interestingly, the simultaneous effect of d-glutamine and L. plantarum A3 on the bacterial diversity and abundance of male mice was significantly higher than that of female mice. In addition, the combination of d-glutamine and L. plantarum A3 can improve the host microecology by enhancing the population of Firmicutes such as Lactobacillus and Lachnospiraceae, reducing the population of Fusobacterium and Bacteroides and affecting metabolic pathways such as AA metabolism and transporter transport. CONCLUSION: d-Glutamine, as a signaling molecule, can better stimulate the endogenous d-glutamine synthesis in mice and be utilized by L. plantarum A3. Furthermore, sex differences in the changes of intestinal microflora are also found in this research. This research sheds some light on the adoption of d-AAs combined with lactic acid bacteria in intestinal tract health treatment. © 2024 Society of Chemical Industry.

Ultrasound-assisted aqueous two-phase extraction of total flavonoids from Tremella fuciformis and antioxidant activity of extracted flavonoids.

Here, the extraction of total flavonoids from Tremella fuciformis (TF) by aqueous two-phase extraction combined with ultrasound is presented. The extraction was optimized via a single-variable approach using the variables of mass fraction of ethanol and NaH2PO4, ultrasonication time, and TF sample amount. Response surface methodology (RSM) was then applied to determine the best conditions for extraction using the following three key parameters: ultrasonication time, ethanol mass fraction, and NaH2PO4 mass fraction. The optimum conditions were as follows: an aqueous two-phase system of ethanol/NaH2PO4, an ethanol mass fraction of 23%, a NaH2PO4 mass fraction of 27.18%, and an extraction time of 8.25 min. Under these conditions, the maximum extraction rate of total flavonoids was 0.158 mg/g. The scavenging rates for superoxide anion and hydroxyl radical, as well as the antioxidant activity of total flavonoids in TF, were studied. Total flavonoids from TF showed some scavenging ability, but the scavenging effects were lower than those of vitamin C (Vc) at the same concentrations. Nevertheless, ultrasound-assisted two-phase extraction was considered an efficient and rapid method that can be used to extract total flavonoids from TF.