The structure, size and solution chemistry of a polysaccharide iron complex(Niferex)

Abstract

A polysaccharide-iron complex(PIC), synthesized by the neutralization of an FeCl 3 carbohydrate solution, is marketed as an oral hematinic(‘Niferex’). The chemistry, structure and solution chemistry of this complex have been examined by a variety of techniques. Elemental analyses are consistent with the report that solid PIC contains ferrihydrite in the core. Treatment of this material with ammonium oxalate yields a small molecular weight material which rapidly becomes a second, larger material, a result also consistent with the idenfication of ferrihydrite in PIC. The complex itself appears to be spherical with diameters ranging from 3 to 10 nm as determined by gel permeation chromatography and electron microscopy. The relationship between the charge and pH on the complex was studied by electrophoresis and acid—base titration. The material is negatively charged and soluble above pH 4.6. Between pH 4.0 and 4.6, PIC is neutral and insoluble, and below 4.0 it is positively charged and soluble. The carbohydrate component apparently contributes to its solubility at near neutral pHs and may be important in the reported bioavailability of the iron in this supplement.