Plant Polyphenol-Polysaccharide Complexes for Inflammatory Bowel Disease: Molecular Interactions, Nano-Delivery Design, and Translational Evidence

CONTEXT: Plant polyphenol-polysaccharide complexes (PPCs) combine polyphenol bioactivity with the protective, mucoadhesive, and microbiota-accessible properties of polysaccharides. However, the literature often groups chemically distinct polyphenols together, extrapolates structure-function relationships across nonequivalent carriers, and interprets concurrent microbiota or short-chain fatty acid changes as causal mechanisms. OBJECTIVE: This review critically evaluated how molecular interactions and measurable structural attributes of PPCs influence gastrointestinal stability, colon-oriented release, biological effects relevant to inflammatory bowel disease (IBD), and translational readiness. DATA SOURCES: Targeted searches of PubMed, Web of Science Core Collection, Scopus, Embase, and the Cochrane Library were completed through July 20, 2026. Peer-reviewed original studies and relevant reviews published in English were considered. DATA EXTRACTION: Evidence was classified as direct PPC evidence, PPC-relevant formulation evidence, or non-PPC mechanistic and engineering evidence. Information on carrier chemistry, payload, structural attributes, release behavior, biological outcomes, and translational considerations was extracted. DATA ANALYSIS: Quantitative findings were compared only when carrier chemistry, payload, test conditions, and outcomes were sufficiently aligned; heterogeneous data were not pooled. Non-covalent assembly and covalent conjugation can alter molecular organization, physicochemical stability, and release, but no universal relationship between degree of substitution and release is supported. Epigallocatechin-3-gallate, quercetin, and anthocyanins require compound-specific carrier selection. PPC and PPC-relevant interventions are associated with changes in NF-κB-related signaling, epithelial-barrier markers, microbiota composition, and individual short-chain fatty acids, whereas receptor- or microbiota-mediated causality remains largely unverified. Responsive platforms also differ in stability, release control, scale-up burden, and clinical readiness. CONCLUSIONS: PPC-based nano-delivery is a promising preclinical approach, but translation requires matched studies linking structure, properties, and release, mediator-level mechanistic validation, standardized characterization, reproducible manufacturing, formulation-specific safety assessment, and comparison with established IBD therapies.