Complexes of Dendrobium officinale anthocyanins and polysaccharides: Structural characteristics, stability, antioxidant properties, and bioavailability

Dendrobium officinale Kimura et Migo has been used extensively in functional foods and garnered significant attention because of its therapeutic properties and nutritional value. Anthocyanins are prone to degradation in environmental and biological conditions, leading to color fading and loss of bioactivity. Forming complexes with endogenous polysaccharides can enhance their stability and protect the color of anthocyanin products. In this study, anthocyanins extracted from D. officinale (DOA) were complexed with D. officinale polysaccharide extract (DOP) to investigate the effects of complexation on the physicochemical properties of the anthocyanins. DOA–DOP complexes were characterized by scanning/transmission electron microscopies, differential scanning calorimetry, dynamic light scattering, and multiple spectroscopies. Stability assessments and simulated in vitro gastrointestinal digestion were performed. Bioactivity was evaluated using a human colon epithelial (Caco-2) cell monolayer model. Spectral analyses revealed hydrogen bonding as the primary interaction in the DOA–DOP complexes. Complexation significantly enhanced DOA retention under light exposure, heat treatment, pH variation, and exposure to metal ions. DOP improved the in vitro antioxidant capacity of DOA. Furthermore, the DOA–DOP complexes exhibited prolonged resistance to upper gastrointestinal digestion and restored lipopolysaccharide-induced epithelial hyperpermeability in the Caco-2 cell model. Collectively, DOA–DOP complexation enhanced D. officinale anthocyanin stability, bioactivity, and colonic bioavailability.