Reaction mass of (E)-3-methyl-4-(2,6,6-trimethylcyclohex-2-en-1-yl)but-3-en-2-one and (E) -1-(2,6,6-trimethylcyclohex-2-en-1-yl)pent-1-en-3-one and (E) -1-(2,6,6-trimethylcyclohex-1-en-1-yl)pent-1-en-3-one

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Ames test (Wagner, 1999) : Negative in 5 strains

HPRT (BASF, 2014) : Negative

Chromosomal Aberration in vitro (Gudi, 2000) : Ambiguous

Genetic toxicity in vivo

Description of key information

In vivo Micronucleus Test (Gudi, 2000) : Negative

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

The genetic toxicity of methylionone was analyzed in a bacterial reverse mutation assay according Ames et al. (Wagner, 1999). The bacteria strains S. typhimurium TA 1535, TA 1537, TA 98 and TA 100 were tested with and without metabolic activation by Aroclor-1254 induced rat liver S9 mix according to the plate incorporation method. Although some cytotoxicity in some strains at higher concentrations were noted, no mutagenic effect of methylionone was detected.

A second Ames test was performed with methyl ionone (Quest, 1980). Methyl ionone was tested in Salmonella typhimurium TA 1535, TA1537, TA1538, TA98, and TA100 with and without metabolic activation (S9) using 0 (solvent control), 0.01, 0.1, 1, or 10 μl/well of the test substance in dimethyl sulphoxide. The number of colonies on each plate was counted and the mean number of revertant colonies per treatment group was calculated. At the tested concentrations, no significant increase in the number of revertant colonies was reported with any of the strains, with or without S9. A slight increase was observed with strain TA1537 at 0.01 ul/plate, and due to this slight increase, a repeat test was conducted at concentrations of 0.005, 0.01, 0.05, and 0.1 ul/plate. No significant increase in the number of revertant colonies was reported at any of the tested concentrations.

It was concluded that no evidence of mutagenic potential of Methyl ionone was obtained in this bacterial test system at the dose levels used.

Methyl ionone 70 (CAS 1335-46-2) was tested in a HPRT test in CHO cells with and without metabolic activation (BASF SE, 2014). Cytotoxicity was found in the absence and presence of S9 mix, at least at the highest applied concentrations. The test substance did not cause any relevant increase in the mutant frequencies in two independent experiments.

In a study using a chromosome aberration assay the genetic toxicity in vitro was analyzed in Chinese hamster ovary cells (Gudi, 2000). The cells were incubated for 4 h or 20 h with 12.5, 25, and 50 ug/ml methyl ionone dissolved in DMSO with and without metabolic activation. 0.1 and 0.2 ug/ml mitomycin C was used as positive control in the non-activated assay and 10 and 20 ug/ml cyclophosphamide in the activated assay. After harvesting the cells, frequencies of cells with structural and numerical aberrations were calculated by analyzing a minimum of 200 metaphase spreads and scoring for chromatid-type and chromosome-type aberrations. The resulting findings were ambiguous, as an induction of structural chromosome aberrations was found in the absence of S9 metabolic activation, but not in the presence of S9 metabolic activation. Furthermore, it was negative in both the absence and presence of S9 metabolic activation for the induction of numerical chromosome aberrations.

The genetic toxicity in vivo was analyzed in mammalian erythrocyte micronucleus test (Gudi, 2000). Five male and five female IRC mice per dose were intraperitoneally injected with 20 ml/kg bw at concentrations of 462.5, 925, or 1850 mg/kg body weight methylionone in corn oil. 24 h and 48 h after dosing, animals were sacrificed and bone marrow cells were isolated from the femurs.

Only a light to moderate reduction (up to 35%) in the ratio of polychromatic erythrocytes to total erythrocytes were observed in some of the methylionone-treated groups relative to the respective vehicle controls. A statistically significant increase in micronucleated  polychromatic erythrocytes (8 MNPCE/10000 PCE) was observed in male mice 24 hrs after treatment with 925 mg/kg. However, this response is not considered biologically relevant (each of the five animals had no more than 3 MPCE, which are within the range of historical solvent control:  0-7 MN/2000 PCE/animal). Also, no significant increase and no dose responsiveness was observed in any other test article treated group regardless of dose level, sex, or bone marrow collection time. Thus, methhylionone could be regarded as not mutagenic in vivo.

Short description of key information:
Genetic toxicity:
- in vitro in bacteria: negative (Ames test)
- in vitro in mammalian cells: negative (HPRT)
- in vitro in mammalian cells: ambigious (chromosome aberration, CHO cells)
- in vivo: negative (MNT)

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Although ambiguous results were found in the chromosome aberration test in mammalian cells in vitro, those foundings were not confirmed in a cytogenicity test in vivo.

Moreover no genetic toxicity could be detected in bacteria as well as in mammalian cells in vitro (HPRT).

Thus, due to overall negative results for genetic toxicity, no classification is required.