Formation of a Copper-Sorbitol Complex in Copper Sulfate-Sorbitol Systems

Previous works in our laboratory have been done to obtain some more valuable information on the state of minerals in food materials.From the view point of the importance of minerals in organisms, as ligands such nitrogen and oxygen compounds as amino acids and sugars are of interest because they occur abundantly in organisms.Among these compounds, several amino acids and sugars have been dealt with in the previous papers; the formation of iron-lactose, 1 ) iron-ascorbic acid, 2 ) copper-glycine, 3 ) zinic-histidine, 4 ) zinc-cysteine, s) and zinc-methionine 6 ) complexes was investigated.Sugar-alcohol, however, has not yet come under examination.Accordingly, in this work, the formation of a copper-sorbitol complex was examined with -CuS04 -sorbitol solutions as the reaction system.As for the copper-sorbitol complex, only a few .studieshave been reported.The formation of the complex is likely to occur in alkaline solutions,?) and its composition is estimated to be 3: 1 8 ) or 2.83: 1 9 ) in the molar ratio of copper to sorbitol.In general, the complex has a tendency to be formed in rather strongly alkaline solutions. 7)-J o) However, such a condition of high pH is not available for considering the formation of this complex during the processing of food materials or in the gastro-intestinal tracts.The pH value of these surrounding media is mostly a weakly acidic or a weakly alkaline one.In this work, therefore, the formation of copper-sorbitol complex under these mild conditions also is examined and the relationship between the solubility and the chemical structure of the complex will be discussed herein.