Contact activation by ellagic acid - the concept of soluble activator disputed

Concentrated, true solutions of ellagic acid (EA) prepared by pH reduction had only a small effect on contact activation initially. However when the EA formed a fine microcrystalline dispersion there was concurrent development of contact activity with turbidity. The dependence of contact activity on EA concentration was found to be a log-log relationship. After relatively low speed centrifugation contact activity-promoting material was decreased from supernatant layers at all concentrations. These findings suggest that EA is not effective as a contact activator when in true solution, but is active only when present as a solid.