Carboxymethylated-kappa-casein: A convenient tool for the identification of polyphenolic inhibitors of amyloid fibril formation

Reduced and carboxymethylated-kappa-casein (RCM-kappa-CN) is a milk-derived amyloidogenic protein that readily undergoes nucleation-dependent aggregation and amyloid fibril formation via a similar pathway to disease-specific amyloidogenic peptides like amyloid beta (A beta), which is associated with Alzheimer's disease. In this study, a series of flavonoids, many known to be inhibitors of A beta fibril formation, were screened for their ability to inhibit RCM-kappa-CN fibrilisation, and the results were compared with literature data on A beta inhibition. Flavonoids that had a high degree of hydroxylation and molecular planarity gave good inhibition of RCM-kappa-CN fibril formation. IC50 values were between 10- and 200-fold higher with RCM-kappa-CN than literature results for A beta fibril inhibition, however, with few exceptions, they showed a similar trend in potency. The convenience and reproducibility of the RCM-kappa-CN assay make it an economic alternative first screen for A beta inhibitory activity, especially for use with large compound libraries. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.