Dendrobium officinale polysaccharide-EGCG complexes: Covalent and non-covalent interactions for enhanced antioxidant properties

The objective of this study was to prepare dendrobium officinale polysaccharide-epigallocatechin-3-gallate (DOP-EGCG) covalent conjugates and non-covalent complexes to enhance the antioxidant properties of the polysaccharide. The conjugates were synthesized via free radical induction, whereas the complexes were formed through physical mixing. The structure and properties of the conjugates and complexes were then characterized. C-H bonds and hydrogen bonds were found to play a crucial role in the formation of the conjugates. Conjugating DOP and EGCG decreased the crystallinity of the polysaccharide and altered the crystal morphology of the polyphenol. The thermal stability of DOP in the EGCG complexes (99.2 °C) was lower than that of free DOP (103.0 °C), whereas that of the DOP in the EGCG conjugates was higher (113.7 °C). The conjugation of EGCG led to an increase in its phenolic content (112.9 ± 1.8 g/kg), which enhanced its antioxidant properties. Indeed, the conjugates had higher antioxidant properties, as seen by an increase in free radical scavenging, reactive oxygen species quenching, and reducing ability, than the complexes. The present study demonstrated that the formation of polysaccharide-polyphenol conjugates could enhance the antioxidant properties of DOP, thereby expanding its range of application as a functional ingredient in foods and beverages. • Dendrobium officinale polysaccharide and epigallocatechin-3-gallate were combined. • DOP-EGCG non-covalent complexes and covalent conjugates were prepared. • DOP-EGCG conjugates were prepared using a free radical-induced method. • Covalent attachment of EGCG significantly enhanced the antioxidant activity of DOP.