In this study, the physicochemical properties of polysaccharides from Houttuynia cordata Thunb. fermented with Lactiplantibacillus plantarum HM6008 (FHCTP) were determined, and the antiallergic activity was evaluated using rat basophilic leukemia (RBL)-2H3 cells. The results showed that fermentation increased the ratio of mannose to sulfate in FHCTP. Compared with H. cordata Thunb. polysaccharides (HCTP), the particle size of FHCTP decreased by 26.67%, and its stability in aqueous solution increased. The inhibition rate of FHCTP on the degranulation of RBL-2H3 cells was significantly higher than that of HCTP, (82.79 ± 5.19)% versus (53.75 ± 1.95)%. After FHCTP intervention, the expression of fragment crystallizable epsilon receptor I (FcεRI) was significantly down-regulated, and the average fluorescence intensity decreased from 2458.00 ± 7.50 to 1495.00 ± 28.50. Both FHCTP and HCTP effectively inhibited the isomerization of cytoskeletal proteins and the increase of intracellular calcium ion concentration. In addition, in the mouse passive cutaneous anaphylaxis assay, FHCTP showed a more significant inhibitory effect on dye extravasation in mouse ears, indicating stronger antiallergic activity. In conclusion, FHCTP has better stabilizing effect on mast cells and effectively alleviates mast cell-mediated passive cutaneous anaphylaxis in mice. The results of this research are expected to promote the development and application of antiallergic products from edible and medicinal materials.

Polysaccharides derived from Porphyra haitanensis exhibit a range of biological activities. However, they are characterized by high molecular weight and low utilization rates. In the present investigation, the degranulation inhibitory activity of Porphyra haitanensis polysaccharides fermented with four distinct Lactobacillus strains were evaluated. The fermentation process culminated in the identification of Lactiplantibacillus plantarum (CGMCC 11217) as the optimal strain. The optimized fermentation parameters were determined as follows: a solid-to-liquid ratio of 1:40, an inoculum concentration of 1%, and a fermentation duration of 12 hours. Subsequently, the physicochemical properties of the polysaccharides were analyzed. Results indicated a significant reduction in the particle size of the polysaccharide post-fermentation, with an average molecular particle size of 2,619.67 ± 242.37 nm. The rat basophil leukemia (RBL)-2H3 cell model was employed to assess the inhibitory capacity of fermented Porphyra haitanensis polysaccharide (FPHSP) on mast cell degranulation. Furthermore, the in vivo efficacy of FPHSP was preliminarily evaluated using the passive cutaneous anaphylaxis (PCA) model. Due to the similar properties and inhibitory degranulation activity of purified FPHSP-2 and FPHSP-3, the two components were mixed to create FPHSP-2/3. FPHSP-2/3 was found to diminish the release of β-hexosaminidase by inhibiting Ca²⁺ influx in Rat basophil leukemia-2H3 cell (RBL-2H3 cells). Additionally, FPHSP-2/3 mitigated the symptoms of mast cell-mediated passive cutaneous anaphylaxis, implying that FPHSP-2/3 may possess enhanced anti-allergic properties in vivo. The present study optimized the fermentation of Porphyra haitanensis polysaccharides by Lactiplantibacillus plantarum, demonstrating a significant reduction in particle size and enhanced anti-allergic activity in vitro and in vivo, suggesting potential for improved utilization of these polysaccharides.