Structural characterization of a novel polysaccharide from Lonicera caerulea L. var. edulis Turcz. ex Herd. fruit and its activity in immune regulation and gut microbiota modulation

Polysaccharides from Lonicera caerulea L. var. edulis Turcz. ex Herd. Fruit (THP) have attracted considerable interest due to their potential health benefits, but the structural characteristics and immunomodulatory mechanisms of these polysaccharides remain poorly understood. This study aimed to isolate and characterize a novel polysaccharide from Lonicera caerulea fruit and evaluate its immunomodulatory activity. A novel polysaccharide (THP-1) was purified from hot-water extracts of Lonicera caerulea fruit and exhibited a number-average molecular weight of 9.17 kilodaltons. Monosaccharide composition analysis revealed that THP-1 was primarily composed of arabinose (84.43%), glucose (12.96%), and galactose (2.61%), with major linkages of 1-linked Araf, 1,5-linked Araf, 1,3,6-linked Galp, and 1,4-linked Galp. In cyclophosphamide-induced immunosuppressed mice, THP treatment significantly increased thymus and spleen indices, ameliorated histological damage in immune organs, and up-regulated the expression of interleukin-1β, interleukin-6, and tumor necrosis factor-α. Furthermore, THP enhanced intestinal barrier integrity by increasing the expression of tight junction proteins including Claudin, Occludin, and ZO-1, and modulated gut microbiota composition by enriching Firmicutes and butyrate-producing bacteria (including Lachnospiraceae and Butyricicoccaceae) while reducing Enterobacteriaceae abundance. The newly extracted THP polysaccharide is a structurally defined bioactive polysaccharide with potent immunomodulatory effects mediated through the enhancement of cytokine production, intestinal barrier function, and beneficial gut microbiota modulation. These findings suggest that polysaccharides from Lonicera caerulea fruit may serve as promising dietary ingredients for improving immune function and maintaining intestinal health.