Fe(Ⅲ) concentrations controlled highly soluble carboxylated inulin–Fe toward efficient supplement of iron

Iron deficiency is the utmost critical problem of nutrition worldwide. Polysaccharide-iron chelate is a promising iron supplementation that exhibits good stability, high absorption rate, and fewer adverse reactions, but it still owns drawbacks of extra energy and lower iron content with respect to inorganic ones. Carboxylated polysaccharide-iron has been proven with enhanced iron content, however with poor aqueous solubility. Here, Fe3+ concentrations controlled highly soluble carboxylated inulin-iron chelates were synthesized to promote the sustained release and efficient supplement of iron with no extra energy. Inulin, soluble dietary fiber, was initially reacted with succinic anhydride (SA) to get carboxylated inulin (IN-SA) consequently enhancing the complexing ability of Fe3+ and its bioavailability. Interestingly, the aqueous solubility of the IN-SA-iron chelate (IN-SA-Fe) directly correlated with the Fe3+ concentrations. Relatively higher or lower Fe3+ concentrations resulted in highly soluble IN-SA-Fe, otherwise, leading to insolubility precipitates. The possible mechanism was proposed as the polymerization reaction of IN-SA in different degrees with Fe3+ acting as the cross-linker. Moreover, IN-SA-Fe was demonstrated with properties of sustained slow-release of iron in artificial gastric juice and good in vivo biosafety. This work provides a simple, efficient, no extra energy soluble iron supplement for the treatment of iron deficiency.