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

Abstract

The objective of this study was to prepare Dendrobium officinale polysaccharide-epigallocatechin-3-gallate (DOP-EGCG) covalent complexes (COV) and non-covalent complexes (NON) to enhance the antioxidant properties of the polysaccharide. The COV samples were synthesized via free radical induction, whereas the NON samples were formed through physical mixing. The structure and properties of the complexes were then characterized. C-H bonds and hydrogen bonds were found to play a crucial role in the formation of the COV samples. The combination of DOP and EGCG reduced the crystallinity of the polysaccharide and altered the crystal morphology of the polyphenol. The thermal stability of the NON samples (99.2 °C) was lower than that of free DOP (103.0 °C), whereas that of the COV samples was higher (113.7 °C). Covalent binding increased the EGCG content of the complexes (112.9 ± 1.8 g/kg), thus improving its antioxidant properties. Indeed, the COV samples exhibited stronger antioxidant activities, as seen by an increase in free radical scavenging, reactive oxygen species quenching, and reducing ability, than the NON samples. The present study demonstrated that the formation of polysaccharide-polyphenol complexes could enhance the antioxidant properties of DOP, thereby expanding its range of application as a functional ingredient in foods and beverages.