Evaluation of the safety of the dietary antioxidant ergothioneine using the bacterial reverse mutation assay

The dietary antioxidant L-(+)-ergothioneine was tested for its potential mutagenic activity using the bacterial reverse mutation assay. The experiments were carried out using histidine-requiring auxotrophic strains of Salmonella typhimurium (Salmonella typhimurium TA98, TA100, TA1535 and TA1537), and the tryptophan-requiring auxotrophic strain of Escherichia coli (Escherichia coli WP2 uvrA) in the presence and absence of a post-mitochondrial supernatant (S9) prepared from livers of phenobarbital/β-naphthoflavone-induced rats. The revertant colony numbers of vehicle control plates with and without S9 Mix were within the corresponding historical control data ranges. The reference mutagen treatments (positive controls) showed the expected, biologically relevant increases in induced revertant colonies in all experimental phases in all tester strains. No biologically relevant increases were observed in revertant colony numbers of any of the five test strains following treatment with L-(+)-ergothioneine at any concentration level, either in the presence or absence of metabolic activation (S9 Mix) in the performed experiments. On the basis of the data reported, it can be concluded that L-(+)-ergothioneine did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used. Thus L-(+)-ergothioneine has no mutagenic activity on the applied bacteria tester strains under the test conditions used in this study. Research is continuing to define the role of L-(+)-ergothioneine in disease pathophysiology. Further studies on its safety are suggested.