Developing ginger polysaccharide-Cr (III) complexes using ginger peel to provide enhanced in vivo anti-inflammatory activity: Fabrication, structural characterization and activity evaluation

The present study aimed to modify the structure of ginger peel polysaccharides (GPPs) with Cr (III) and to evaluate the in vivo anti-inflammatory activities of the GPPs and GPP-Cr (III) complexes and their underlying mechanisms. The response surface methodology optimized the preparation process to a GPPs-Cr (III) mass ratio of 1:0.06, a temperature of 60 °C, and a pH of 6.8, with the greatest chelation rate of 91.1%. The modification of Cr (III) increased the molecular weight and altered the glucose proportion of the GPPs, through targeting the O–H of hydroxyl groups and affecting the C–O/O–C–O structures. The GPP-Cr (III) complexes had a similar crystallinity and conformation to the parent polysaccharides, but were more thermally stable than the GPPs (in the region of < 130 °C and > 332 °C). In CuSO4-induced inflammation in zebrafish, the GPP-Cr (III) complexes (dose: 50 and 100 μg/mL) showed significantly stronger anti-inflammatory activity than the GPPs did via down-regulating the expression of relevant transcription factors and cytokines in the MyD88/NF-κB/MAPK/iNOS signaling pathway. Therefore, GPP-Cr (III) complexes might be promising dietary formulations with anti-inflammatory effects, Cr (III) supplements, or functional food components, which substantially facilitated the high-value utilization of ginger peel by-products.