2,6-dimethylhept-5-enal

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

In vitro Ames: Negative.

In vitro UDS: Negative.

In vivo Micronucleus test: Negative.

Read across Carcinogenicity study: Negative

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 September 2005 - 11 October 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

S9

Test concentrations with justification for top dose:

3; 10; 33; 100; 333; 1000; 2500; and 5000 µg/plate

Vehicle / solvent:

DMSO (MERCK, D- 64293 Darmstadt; pUiity > 99 % ). The solvent 'vvas chosen because of its solubility properties and its relative non-toxicity to the bacteria.

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

methylmethanesulfonate

other: 4-nitro-o-phenylene-diamine, 2-aminoanthracene

Details on test system and experimental conditions:

Standard Ames conditions.

Rationale for test conditions:

As per Ames original protocol.

Evaluation criteria:

Statistical Dunnetts test.

Statistics:

Statistical Dunnetts test.

Key result

Species / strain:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

DISCUSSION OF RESULTS

The test item Melonal was assessed for its potential to induce gene mutations in the plate incorporation test (experiment I) and the pre-incubation test (experiment 11) using Salmonella typhimurium strains TA 1535, TA 1537, TA 98, and TA 100, and the Escherichia coli strain WP2 uvrA.

The assay was performed in two independent experiments both with and without liver microsomal activation. Each concentration and the controls were tested in triplicate. The test item was tested at the following concentrations:

Pre-Experiment/ Experiment I and II: 3; 10; 33; 100; 333; 1000; 2500; and 5000 µg/plate

The plates incubated with the test item showed reduced background growth at the following concentrations (µg/plate):

Strain	Experiment I		Experiment II
	without S9 mix	with S9 mix	without S9 mix	with S9 mix
TA 1535	2500-5000	2500-5000	333-5000	1000-5000
TA 1537	2500-5000	2500-5000	333-5000	333-5000
TA 98	2500-5000	2500-5000	333-5000	1000-5000
TA 100	2500-5000	2500-5000	333-5000	333-5000
WP2 uvrA	2500-5000	2500-5000	333-5000	333-5000

 

Toxic effects, evident as a reduction in the number of revertants, occurred in the test groups with and without metabolic activation at the following concentrations (µg/plate):

Strain	Experiment I		Experiment II
	without S9 mix	with S9 mix	without S9 mix	with S9 mix
TA 1535	5000	2500-5000	1000-5000	1000-5000
TA 1537	2500-5000	2500-5000	333-5000	1000-5000
TA 98	2500-5000	2500-5000	1000-5000	1000-5000
TA 100	2500-5000	2500-5000	333-5000	1000-5000
WP2 uvrA	2500-5000	2500-5000	5000	2500-5000

 

No substantial increase in revertant colony numbers of any of the five tester strains was observed following treatment with Melonal at any dose level, neither in the presence nor absence of metabolic activation (S9 mix). There was also no tendency of higher mutation rates with increasing concentrations in the range below the generally acknowledged border of biological relevance.

Appropriate reference mutagens were used as positive controls. They showed a distinct increase of induced revertant colonies.

In experiment 11, the data in the negative control of strain WP2 uvrA with metabolic activation were slightly above our historical control range. Since this deviation is rather small, this effect is considered to be based upon biologically irrelevant fluctuations in the number of colonies.

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.

Conclusions:

Interpretation of results (migrated information):
negative

During the described mutagenicity test and under the experimental conditions reported, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.
Melonal is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.

Executive summary:

This study was performed to investigate the potential of Melonal to induce gene mutations in the plate incorporation test (experiment I) and the pre-incubation test (experiment 11) using the Salmonella typhimurium strains TA 1535, TA 1537, TA 98, and TA 100, and the Escherichia coli strain WP2 uvrA.

The assay was performed in two independent experiments both with and without liver microsomal activation. Each concentration, including the controls, was tested in triplicate.

The test item was tested at the following concentrations:

Pre-Experiment/Experiment I and II: 3; 10; 33; 100; 333; 1000; 2500; and 5000 µg/plate

The plates incubated with the test item showed reduced background growth at higher concentrations with and without metabolic activation in both independent experiments.

Strong toxic effects, evident as a reduction in the number of revertants, occurred in the test groups with and without metabolic activation in both experiments.

No substantial increase in revertant colony numbers of any of the five tester strains was observed following treatment with Melonal at any dose level, neither in the presence nor absence of metabolic activation (S9 mix). There was also no tendency of higher mutation rates with increasing concentrations in the range below the generally acknowledged

border of biological relevance.

Appropriate reference mutagens were used as positive controls and showed a distinct increase of induced revertant colonies.

 

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.

Therefore, Melonal is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

In vitro Ames: Negative. In vitro UDS: Negative. In vivo Micronucleus test: Negative.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vitro:

During the described mutagenicity test and under the experimental conditions reported, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used. Melonal is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.

Reading across to Citral, a structural analogue, a two year carcinogenicity study shows Citral was not carcinogenic in F344/N rats or male B6C3Fl mice, implying the material should also not be considered mutagenic. Thus it is inferred that melonal should also be considered non mutagenic.

With this read across information in support of the existing Ames result, Melonal is considered not classified for Mutagenicity.

Justification for selection of genetic toxicity endpoint
GLP study performed on the target substance (not read across)

Justification for classification or non-classification

Based on the evidence provided by the negetive in vitro Ames, in vitro UDS and in vivo micronucleus assays and also the read across to the 2 year carcinogenicity study on structural analog Citral, it can be considered that this substance does not show potential for mutgenicty.

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