A sulfated polysaccharide from abalone influences iron uptake by the contrary impacts of its chelating and reducing activities.

Polysaccharides with different structures have been reported to regulate iron uptake in opposite direction. The present study investigated the interaction between a sulfated polysaccharide (AGSP) from marine shellfishes and Fe(III)/Fe(II) in order to reveal the mechanism for the effect of AGSP on iron bioavailability. The Fe(III) chelating activity and resulting Fe(III)-chelates of AGSP and its desulfated derivative (dS-AGSP) were studied, their ferric reducing activity and Fe(II) chelating activity were compared, and their inhibition effects on the Fe absorption were evaluated by using Caco-2 cell models treated with Fe(III) and Fe(II). As indicated by the results, polysaccharides could chelate Fe(III) with the sulfate and carboxyl groups via FeO bond along with conformation change, resulting in unstable particles. Both AGSP and dS-AGSP inhibited the iron uptake in a dose-dependent manner. Notably, the chelating property of polysaccharides showed a negative correlation with the iron bioavailability while their reducing capability demonstrated a positive correlation. Moreover, sulfate substitution enhanced the chelating and reducing capabilities so to regulate the effects of AGSP on Fe absorption in contradictory ways. Thus, the present study elucidated the mechanism of the influence of AGSP on bioavailability of non-heme iron.