Potassium 3,5,5-trimethylhexanoate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Potassium 3,5,5-trimethylhexanoate is considered to be non-mutagenic in this bacterial reverse mutation assay.

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Specific details on test material used for the study:

Name: Potassium 3,5,5-trimethylhexanoate
CAS No.: 93918-10-6
Batch No.: PURS151015
Purity: 99.4%
Physical State: solid
Colour: white
Molecular Weight: 196.33 g/mol
Storage Conditions: room temperature
Re-certification Date: 14 October 2016

Target gene:

The Salmonella typhimurium histidine (his) reversion system measures his- → his+ reversions. The S. typhimurium strains are constructed to differentiate between base pair (TA 100, TA 1535, TA 102) and frameshift (TA 98, TA 1537) mutations.

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

Mammalian Microsomal Fraction S9 Mix

Test concentrations with justification for top dose:

The toxicity of the test item was determined with tester strains TA 98 and TA 100 in a pre-experiment. Eight concentrations were tested for toxicity and induction of mutations with three plates each. The experimental conditions in this pre-experiment were the same as described below for the main experiment I (plate incorporation test). Toxicity may be detected by a clearing or rather diminution of the background lawn or a reduction in the number of revertants down to a mutation factor of approximately ≤ 0.5 in relation to the solvent control. The test item was tested in the pre-experiment with the following concentrations:
3.16, 10.0, 31.6, 100, 316, 1000, 2500 and 5000 µg/plate
The test item concentrations to be applied in the main experiments were chosen according to the results of the pre-experiment (see chapter 12.1.1 Pre-Experiment). 5000 µg/plate was selected as the maximum concentration. The concentration range covered two logarithmic decades. Two independent experiments were performed with the following concentrations:
31.6, 100, 316, 1000, 2500 and 5000 µg/plate
As the results of the pre-experiment were in accordance with the criteria described above, these were reported as a part of the main experiment I.

Vehicle / solvent:

Aqua destillata (purified water)

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

not specified

Positive controls:

yes

Positive control substance:

sodium azide

methylmethanesulfonate

other: 1. 4-NOPD; 4-nitro-o-phenylene-diamine 2. 2-AA; 2-aminoanthracene

Details on test system and experimental conditions:

Five strains of S. typhimurium with the following characteristics were used:

TA 98: his D 3052; rfa-; uvrB-; R-factor: frame shift mutations
TA 100: his G 46; rfa-; uvrB-; R-factor: base-pair substitutions
TA 1535: his G 46; rfa-; uvrB-: base-pair substitutions
TA 1537: his C 3076; rfa-; uvrB-: frame shift mutations
TA 102: his G 428 (pAQ1); rfa-; R-factor: base-pair substitutions

Tester strains TA 98, TA 1535 and TA 102 were obtained from MOLTOX, INC., NC 28607, USA. Tester strains TA 100 and TA 1537 were obtained from Xenometrix AG, Switzerland. They were stored as stock cultures in ampoules with nutrient broth (OXOID) supplemented with DMSO (approx. 8% v/v) over liquid nitrogen.

All Salmonella strains contain mutations in the histidine operon, thereby imposing a requirement for histidine in the growth medium. They contain the deep rough (rfa) mutation, which deletes the polysaccharide side chain of the lipopolysaccharides of the bacterial cell surface. This increases cell permeability of larger substances. The other mutation is a deletion of the uvrB gene coding for a protein of the DNA nucleotide excision repair system resulting in an increased sensitivity in detecting many mutagens. This deletion also includes the nitrate reductase (chl) and biotin (bio) genes (bacteria require biotin for growth). The tester strains TA 98, TA 100 and TA 102 contain the R-factor plasmid, pkM101. These strains are reverted by a number of mutagens that are detected weakly or not at all with the non R-factor parent strains. pkM101 increases chemical and spontaneous mutagenesis by enhancing an error-prone DNA repair system which is normally present in these organisms. The properties of the S. typhimurium strains with regard to membrane permeability, ampicillin- and tetracycline-resistance as well as normal spontaneous mutation rates are checked regularly according to Ames et al.. In this way it is ensured that the experimental conditions set up by Ames are fulfilled.

Evaluation criteria:

Evaluation of Mutagenicity
The Mutation Factor is calculated by dividing the mean value of the revertant counts by the mean values of the solvent control (the exact and not the rounded values are used for calculation).
A test item is considered as mutagenic if:
- a clear and dose-related increase in the number of revertants occurs and/or
- a biologically relevant positive response for at least one of the dose groups occurs
in at least one tester strain with or without metabolic activation.

A biologically relevant increase is described as follows:
- if in tester strains TA 98, TA 100 and TA 102 the number of reversions is at least twice as high
- if in tester strains TA 1535 and TA 1537 the number of reversions is at least three times higher
than the reversion rate of the solvent control.

A test is considered acceptable if for each strain:
- the bacteria demonstrate their typical responses to ampicillin (TA 98, TA 100, TA 102)
- the negative control plates (A. dest.) with and without S9 mix mean values of the spontaneous reversion frequency are within the historical control data range (2012 -2014).
- corresponding background growth on negative control, solvent control and test plates is observed
- the positive controls show a distinct enhancement of revertant rates over the control plate
- at least five different concentrations of each tester strain are analysable.

Statistics:

According to OECD guidelines, the biological relevance of the results is the criterion for the interpretation of results, a statistical evaluation of the results is not regarded as necessary. A test item producing neither a dose related increase in the number of revertants nor a reproducible biologically relevant positive response at any of the dose groups is considered to be non-mutagenic in this system.

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: Plate-incorporation Test

The test item Potassium 3,5,5-trimethylhexanoate was investigated for its potential to induce gene mutations according to the plate incorporation test (experiment I) and the pre-incubation test (experiment II) using Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA 1537 and TA 102. In two independent experiments several concentrations of the test item were used. Each assay was conducted with and without metabolic activation. The concentrations, including the controls, were tested in triplicate. The following concentrations of the test item were prepared and used in the experiments:

31.6, 100, 316, 1000, 2500 and 5000 µg/plate

No precipitation of the test item was observed in any tester strain used in experiment I and II (with and without metabolic activation). No toxic effects of the test item were noted in any of the five tester strains used up to the highest dose group evaluated with and without metabolic activation in experiment I and II. The reduction in the number of revertants down to a mutation factor of ≤ 0.5 found in experiment I in tester strains TA 1535 and TA 1537 at a concentration of 1000 µg/plate (with metabolic activation) was regarded as not biologically relevant due to lack of a dose-response relationship.

No biologically relevant increases in revertant colony numbers of any of the five tester strains were observed following treatment with Potassium 3,5,5-trimethylhexanoate at any concentration level, neither in the presence nor absence of metabolic activation in experiment I and II. The reference mutagens induced a distinct increase of revertant colonies indicating the validity of the experiments.

Conclusions:

Potassium 3,5,5-trimethylhexanoate is considered to be non-mutagenic in this bacterial reverse mutation assay.

Executive summary:

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, Potassium 3,5,5-trimethylhexanoate did not cause gene mutations by base pair changes or frameshifts in the genome of the tester strains used. Therefore, Potassium 3,5,5-trimethylhexanoate is considered to be non-mutagenic in this bacterial reverse mutation assay.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)