IntroductionSeveral alkenylbenzenes, including methyleugenol (ME), are present in a wide range of botanicals and exhibit carcinogenic and mutagenic properties. Negative results are generally obtained for alkenylbenzenes in standard in vitro genotoxicity tests, including the Ames test. A lack of mutagenicity observed in such tests is thought to result from impaired metabolic activation of alkenylbenzenes via hydroxylation, with subsequent sulfoconjugation to its ultimate mutagenic or carcinogenic form. Although recent studies have reported the mutagenicity of hydroxylated ME metabolites in the Ames test using modified TA100 strains expressing human sulfotransferases (SULTs), to our knowledge, the detection of ME mutagenicity has not yet been reported.FindingsUsing strain TA100-hSULT1C2, which expresses human SULT1C2, we optimized the protein content of S9 Mix and the pre-incubation time required to promote metabolic activation in the Ames test. This procedure enabled us to obtain a positive response with ME.ConclusionsWe established Ames-test conditions enabling the detection of ME-induced mutagenicity, using a strain expressing human SULT1C2 in the presence of induced-rat S9 Mix. This simple approach will help assess the mutagenicity of other alkenylbenzenes and related chemicals.

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-Ubidecarenone (coenzyme Q10) has been widely used as a complementary therapy in heart failure and as a dietary supplement for over two decades. Ubidecarenone is manufactured by organic synthesis, yeast (non-Saccharomyces cerevisiae) fermentation, or bacteria fermentation. There are many reports on the safety of ubidecarenone. However, genotoxicity of ubidecarenone manufactured by bacteria fermentation has not been reported. We carried out genotoxicity evaluation of ubidecarenone manufactured by bacteria fermentation through the bacterial reverse mutation test (Ames test) and in vitro chromosome aberration test in compliance with the Japanese guidelines on genotoxicity testing of phartesting chemicals. The results indicate neither increase of revertant colonies nor chromosome aberration, suggesting that the ubidecarenone manufactured by bacteria fermentation has no genotoxic activities under the condition of this study.