Toxic Effects of Natural Food Dyes on Paramecium caudatum

Abstract

The toxicity of 14 commercial natural dyes which are widely used as food additives in Japan was studied on Paramecium caudatum. Laccaic acid and capsanthin were found to be very toxic to P. caudatum. Some of the commercially available carminic acid and crocin samples were also toxic. The effects of natural food dyes on leucine aminopeptidase, acid phosphatase, γ-glutamyl transpeptidase and esterase activities extracted from P. caudatum were studied in order to investigate the mechanism of toxicity. The inhibitory effects of natural food dyes on leucine aminopeptidase, acid phosphatase and esterase in vitro were proportional to the toxic effects of the dyes expressed in terms of the survival time of P. caudatum. Low concentrations of laccaic acid (B Co. Ltd.) and carminic acid (A Co. Ltd.) inhibited γ-glutamyl transpeptidase activity completely. The purity of the commercial natural food dyes was analyzed by high performance liquid chromatography and X-ray fluorescence spectrometry, and the differences in toxicity are discussed in relation to the components of the dyes.