A red dye from lichens may reduce the abundance of small toxic protein aggregates associated with Alzheimer's disease, researchers in Germany suggest. Dr. Jan Bieschke of the Max Delbruck Center for Molecular Medicine in Berlin-Buch; Dr. Martin Herbst of Charite -- Universitatsmedizin Berlin; and Professor Erich Wanker in Berlin said the dye, a compound called orcein, used for centuries to color fabrics and food, and a related substance, called O4, bind to the amyloid aggregates. Amyloid aggregates are considered to be toxic and cause neuronal dysfunction and memory impairment in Alzheimer's disease, the researchers said. Wanker and colleagues discovered a few years ago that Epigallocatechin-3-gallate, a natural chemical compound found in green tea, renders toxic protein assemblies non-toxic. With orcein and O4, the researchers found another mechanism to eliminate small toxic protein aggregates. Instead of remodeling protein plaques, the dyes reduce the abundance of small, toxic precursor protein assemblies by accelerating the formation of large plaques, the researchers said. "This is a new mechanism," Wanker said in a statement. "Up to now it has been considered to be very difficult to stop the formation of small toxic protein assemblies. If our hypothesis is correct that the small aggregates, which are precursors of plaques, indeed cause neuronal death, with O4 we would have a new mechanism to attack the disease." The findings were published in Nature Chemical Biology.