Anti-Inflammatory Activity of In Vitro Digested Manna in a Caco-2 and RAW264.7 Cells Co-Culture Model of Inflammatory Bowel Disease

Ethnopharmacological relevance: Manna, a natural product derived from Fraxinus species, is traditionally recognized for its ethnomedical use and health-promoting properties, including anti-inflammatory and antioxidant activities attributed to its (poly)phenolic richness.Objective: This study investigates its potential role in managing inflammatory bowel disease (IBD).Material and methods: Manna was purified using a patented procedure and subsequently subjected to in vitro gastrointestinal digestion (INFOGEST 2.0) to obtain the bioaccessible fraction of manna (BFM). The anti-inflammatory properties of the BFM were assessed using an in vitro co-culture model comprising Caco-2 intestinal cells and lipopolysaccharide (LPS)-activated RAW264.7 macrophages, mimicking IBD-associated inflammation. Experiments included pre-treatment with BFM and co-treatment with budesonide, a conventional IBD corticosteroid.Results: BFM pre-treatment significantly reduced LPS-induced interleukin-8 (IL-8) secretion in Caco-2 cells, and interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in RAW264.7 macrophages. BFM also improved redox balance in Caco-2 cells by decreasing inducible nitric oxide synthase (iNOS) levels, nitrogen oxides (NOx) release, and reactive oxygen species (ROS) generation, alongside upregulating occludin to stabilize tight junctions. Mechanistically, BFM downregulated nuclear factor-kappa B (NF-κB)-cyclooxygenase-2 (COX-2)-prostaglandin E2 (PGE2) signaling. Co-treatment with BFM and budesonide showed antagonistic effects on most markers, but an additive and synergistic action was observed in ROS and NOx reduction.Conclusion: Manna exhibits potent anti-inflammatory activity at a low, non-laxative dose (3.8 g/day). These findings underscore its promising nutraceutical potential for the management of IBD.