Red-Beet Betalain Pigments Inhibit Amyloid-beta Aggregation and Toxicity in Amyloid-beta Expressing Caenorhabditis elegans

Betalain pigments are mainly produced by plants belonging to the order of Caryophyllales. Betalains exhibit strong antioxidant activity and responds to environmental stimuli and stress in plants. Recent reports of antioxidant, anti-inflammatory and anti-cancer properties of betalain pigments have piqued interest in understanding their biological functions. We investigated the effects of betalain pigments (betanin and isobetanin) derived from red-beet on amyloid-beta (A beta) aggregation, which causes Alzheimer's disease. Non-specific inhibition of A beta aggregation against A beta 40 and A beta 42 by red-beet betalain pigments, in vitro was demonstrated using the thioflavin t fluorescence assay, circular dichroism spectroscopy analysis, transmission electron microscopy and nuclear magnetic resonance (NMR) analysis. Furthermore, we examined the ability of red-beet betalain pigments to interfere with A beta toxicity by using the transgenic Caenorhabditis elegans model, which expresses the human A beta 42 protein intracellularly within the body wall muscle. It responds to A beta-toxicity with paralysis and treatment with 50 mu M red-beet betalain pigments significantly delayed the paralysis of C. elegans. These results suggest that betalain pigments reduce A beta-induced toxicity.