Isolation, characterization and bioactivities of a new polysaccharide from Annona squamosa and its sulfated derivative

•A novel polysaccharide from pulp tissues of Annona squamosa.•The structural characterization of ASPW80-1 was conducted.•A novel modified polysaccharide namely ASPW80-M1 was also synthesized.•The ultrastructure of ASPW80-1 and ASPW80-M1 was investigated by scanning electron microscope (SEM) and atomic force microscopy (AFM).•Antioxidant and immunostimulatory activities of ASPW80-1 and ASPW80-M1 were evaluated.

A new water-soluble polysaccharide, designated as ASPW80-1, was first isolated from the fruit pulp of Annona squamosa. The structure of ASPW80-1 was elucidated based on the physicochemical and instrumental analyses. The results indicated that ASPW80-1 was a homogeneous heteropolysaccharide with an average molecular weight of 2.29 × 105 Da. Another novel modified polysaccharide, the sulfated derivative of ASPW80-1 namely as ASPW80-M1, was also synthesized. The ultra-structures of both ASPW80-1 and ASPW80-M1 were further characterized by scanning electron microscopy and atomic force microscopy. The antioxidant assays showed that ASPW80-1 and ASPW80-M1 exhibited DPPH and hydroxyl radicals scavenging activities. The results of immunomodulatory assays in vitro showed that ASPW80-1 and ASPW80-M1 could markedly promote the proliferation of mouse splenocytes. These results proposed that ASPW80-M1 might be proposed to be developed as a potential value-added product with the activities of immunomodulator and free-radical inhibitors.