In vitro toxicity evaluation of a product obtained from carmoisine using Tetrahymena pyriformis cells

The toxicity of carmoisine and of its metabolites after interaction with media components, was studied using the single cell system of Tetrahymena pyriformis. Carmoisine was not toxic to T. pyriformis. However, when autoclaved with media components such as bactopeptone or yeast extract, it gave rise to product(s) that completely inhibited the growth of T. pyriformis. Addition of glucose to the bactopeptone-carmoisine mixture before autoclaving significantly enhanced the formation of the toxic product. A similar effect was observed with other reducing sugars and with compounds containing sulfhydryl groups. The results indicate that carmoisine may undergo initial reduction, followed by a series of reactions leading to the formation of the toxic component(s).