Structural characterization and anti-inflammatory effects of Enteromorpha prolifera polysaccharide-Fe/Zn complexes

The structure of polysaccharide has a great influence on its biological functions, and the chelation with metal ions is an effective way to change polysaccharide structural configuration. Herein, the structure of Enteromorpha prolifera polysaccharide (EP)-Fe/Zn complexes were characterized and the results showed that the iron (III) existed in form of β-FeOOH in EP-Fe (III) complex and the zinc (II) existed in form of C-O-Zn in EP-Zn (II) complex. Besides, the chelation with iron (III) or zinc (II) completely changed the apparent forms, and improved the thermal stability of EP. Furthermore, the anti-inflammatory activities of EP, EP-Fe and EP-Zn were proved by a lipopolysaccharide (LPS)-induced RAW264.7 macrophages model. The results showed that EP, EP-Fe (III) and EP-Zn (II) could decrease the mitochondrial membrane potential and the secretion of NO and cytokines induced by LPS. One of the anti-inflammatory mechanisms of EP, EP-Fe (III) and EP-Zn (II) was that they could inhibit mitogen-activated protein kinase (MAPK) signaling pathway via increasing its inhibitor content in cells. Collectively, the research suggested that the chelation with iron (III) or zinc (II) could change the structure and improve the anti-inflammatory activities of EP.