Structural elucidation, antioxidant and neuroprotective features of <i>Physalis pubescens</i> L. polysaccharide and its selenium-modified product

A novel polysaccharide, named as PPFP, was isolated from <i>Physalis pubescens</i> L. fruits with a molecular weight of 229.3 kDa. Further Structural characterisation revealed that PPFP comprised of rhamnose, arabinose, fucose, mannose and glucose, and the predominantly backbone is linked with 1 → 3- and 1 → 6-glycosidic bonds. Using the HNO₃–Na₂SeO₃ method, the selenium-modified derivative (Se-PPFP) was successfully synthesised with higher bioavailability. FT-IR and NMR analyses confirmed selenium was attached to the Se-PPFP structure with the Se=O and O–Se–O forms. More specifically, selenium was bound to the C-6 bond on the D-pyranose of PPFP. Se-PPFP showed reduced molecular weight, looser microstructure and better thermal stability than PPFP. PPFP and Se-PPFP exhibited notable antioxidant and neuroprotective effects, with Se-PPFP being more significant. These findings suggest their potential as functional food antioxidants.