A study on the toxicity of natural food dyes--toxicity and enzyme inhibition in Paramecium caudatum.

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 Paramecium caudatum. Some of the commercially available carminic acid and crocin were also toxic. The inhibitory effect of natural food dyes on leucine aminopeptidase, acid phosphatase and esterase in vitro was proportional to the toxic effect of the dyes on the survival time of Paramecium caudatum. Analyses of the commercial natural food dyes by high performance liquid chromatography failed to identify the toxic components.