INHIBITORY ACTIVITY OF ALGINATES AGAINST THE FORMATION OF CALCIUM-PHOSPHATE

The effect of alginates, a dietary fiber, on calcium phosphate formation was investigated, and compared with that of the well-known inhibitors, poly-L-glutamate and citrate. First, the amount of calcium phosphate precipitate was measured at various alginate concentrations. An alginate delayed the formation of the calcium phosphate precipitate as well as poly-L-glutamate could. Second, the induction time (i.t.), when the transition of amorphous calcium phosphate to the crystalline form would occur, was measured in base titration experiments. Alginates delayed i.t., again as well as poly-L-glutamate could. These results indicate that alginates were an inhibitor of calcium phosphate formation. The plot of i.t. vs. alginate concentration was sigmoidal, which is similar to that of i.t. Vs. poly-L-glutamate concentration and different from that of i.t. vs. citrate concentration. The induction time increase was slight at molar ratios of calcium to uronate above approximately 1/2. This indicates that the interaction between the uronate residue and calcium ion played an important role in the inhibition of calcium phosphate formation by alginates.