Butanoic acid, 2-ethyl-, magnesium salt (2:1)

Genetic toxicity: in vitro

Administrative data

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:

2008/07/14-2008/07/30

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

UK GLP standards (Schedule 1, Good Laboratory Practice Regulations 1999 (SI 1999/3106 as amended by SI 2004/0994)).

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

[(2-ethylbutanoyl)oxy]magnesio 2-ethylbutanoate

EC Number:

700-021-1

Cas Number:

79992-76-0

Molecular formula:

C12H22O4Mg

IUPAC Name:

[(2-ethylbutanoyl)oxy]magnesio 2-ethylbutanoate

Method

Target gene:

Histidine operon for Salmonella
Tryptophan for E. Coli

Species / strain

Species / strain / cell type:

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

Details on mammalian cell type (if applicable):

Not applicable

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

phenobarbitone/Beta­naphthoflavone induced rat liver S9

Test concentrations with justification for top dose:

Range-finding test: 0, 0.15, 0.5, 1.5, 5, 15, 50, 150, 500, 1500, 5000 micro.g/plate
Main test: 0, 50, 150, 500, 1500, 5000 micro.g/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used:
Sterile distilled water.
- Justification for choice of solvent/vehicle:
Material was fully soluble in sterile distilled water ag 50 mg/ml

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: N-ethyl-N'nitro-N-nitroguanidine; 9-aminoacridine; 4-Nitroquinoline-1-oxide; 2-aminoanthracene and Benzo(a)pyrene

Remarks:

Multiple positive control substances.

Details on test system and experimental conditions:

METHOD OF APPLICATION:
The test material was fully soluble in sterile distilled water at 50 mg/ml in solubility checks performed in-house. Sterile distilled water was therefore selected as the vehicle.

The test material was accurately weighed and approximate half-log dilutions prepared in sterile distilled water by mixing on a vortex mixer and sonication for 10 minutes at room temperature on the day of each experiment. Formulated concentrations were adjusted to allow for the stated water/impurity content (4%) of the test material. Analysis for concentration, homogeneity and stability of the test material formulations is not a requirement of the test guidelines and was, therefore, not determined.

Vehicle and positive controls were used in parallel with the test material. A solvent treatment group was used as the vehicle control and the positive control materials used in the series of plates without S9-mix, were as follows:
N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG): 2 µg/plate for WP2uvrA-, 3 µg/plate for TA100
and 5 µg/plate for TA1535
9-Aminoacridine (9AA): 80 µg/plate for TA1537
4-Nitroquinoline-1-oxide (4NQO): 0.2 µg/plate for TA98

In addition, 2-Aminoanthracene (2AA) and Benzo(a)pyrene (BP), which are non-mutagenic in the absence of metabolising enzymes, were used in the series of plates with S9-mix at the following concentrations:
2AA at 1 µg/plate for TA100
2AA at 2 µg/plate for TA1535 and TA1537
2AA at 10 µg/plate for WP2uvrA-
BP at 5 µg/plate for TA98


DURATION
- Preincubation period:
yes
- Exposure duration:
48-72 hours
- Expression time (cells in growth medium):
Not applicable
- Selection time (if incubation with a selection agent):
not applicable
- Fixation time (start of exposure up to fixation or harvest of cells):
48-72 hours

SELECTION AGENT (mutation assays):
Not applicable
SPINDLE INHIBITOR (cytogenetic assays):
Not applicable
STAIN (for cytogenetic assays):
Giemsca

NUMBER OF REPLICATIONS:
Triplicate

NUMBER OF CELLS EVALUATED:
Not applicable

DETERMINATION OF CYTOTOXICITY
- Method:
Lawn deficiency and colony reduction.


OTHER EXAMINATIONS:
None.


OTHER:
Not applicable

Evaluation criteria:

There are several criteria for determining a positive result, such as a dose-related increase in revertant frequency over the dose range tested and/or a reproducible increase at one or more concentrations in at least one bacterial strain with or without metabolic activation. Biological relevance of the results will be considered first, statistical methods, as recommended by the UKEMS (5) can also be used as an aid to evaluation, however, statistical significance will not be the only determining factor for a positive response.
A test material will be considered non-mutagenic (negative) in the test system if the above criteria are not met.
Although most experiments will give clear positive or negative results, in some instances the data generated will prohibit a definitive judgement about the test material activity. Results of this type will be reported as equivocal.

Statistics:

-Acceptance Criteria
The reverse mutation assay may be considered valid if the following criteria are met:
All tester strain cultures exhibit a characteristic number of spontaneous revertants per plate in the vehicle and untreated controls. Acceptable ranges are presented in the standard test method section 3 with historical control ranges for 2006 and 2007 presented in Appendix 2.
The appropriate characteristics for each tester strain have been confirmed, eg rfa cell-wall mutation and pKM101 plasmid R-factor etc.
All tester strain cultures should be in the approximate range of 1 to 9.9 x 109 bacteria per ml.
Each mean positive control value should be at least twice the respective vehicle control value for each strain, thus demonstrating both the intrinsic sensitivity of the tester strains to mutagenic exposure and the integrity of the S9-mix. The positive control historical ranges for 2006 and 2007 are presented in Appendix 2.
There should be a minimum of four non-toxic test material dose levels.
There should not be an excessive loss of plates due to contamination.

Results and discussion

Test results

Test results 1

Species / strain:

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

Test results 2

Species / strain:

E. coli WP2 uvr A

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: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

Preliminary ToxicityTest

The test material was non-toxic to the strains of bacteria used (TA100 and WP2uvrA^-). The test material formulation and S9-mix used in this experiment were both shown to be sterile.

The numbers of revertant colonies for the toxicity assay were:

With (+) or without (-) S9-mix	Strain	Dose (µg/plate)
		0	0.15	0.5	1.5	5	15	50	150	500	1500	5000
-	TA100	141	130	131	159	159	152	145	148	137	135	130
+	TA100	126	150	147	146	133	104	130	117	122	131	120
-	WP2uvrA^-	32	45	25	19	31	31	36	34	36	31	30
+	WP2uvrA^-	42	46	44	45	32	40	35	38	30	22	29

MutationTest

Prior to use, the master strains were checked for characteristics, viability and spontaneous reversion rate (all were found to be satisfactory). These data are not given in the report. The amino acid supplemented top agar and the S9-mix used in both experiments was shown to be sterile.

Results for the negative controls (spontaneous mutation rates) are presented in Table1 (see attachments) and were considered to be acceptable. These data are for concurrent untreated control plates performed on the same day as the Mutation Test.

The individual plate counts, the mean number of revertant colonies and the standard deviations for the test material, vehicle and positive controls both with and without metabolic activation, are presented in Table 2 to Table 5 (see attachments) with the results also expressed graphically in Figure 1 to Figure 4 (see attachments).

Information regarding the equipment and methods used in these experiments as required by the Japanese Ministry of Economy, Trade and Industry and Japanese Ministry of Health, Labour and Welfare are presented in Appendix 1 (see attachments).

A history profile of vehicle and positive control values is presented in Appendix 2 (see attachments).

The test material caused no visible reduction in the growth of the bacterial background lawn at any dose level. The test material was, therefore, tested up to the maximum recommended dose level of 5000 µg/plate. No test material precipitate was observed on the plates at any of the doses tested in either the presence or absence of S9-mix.

No significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, at any dose level either with or without metabolic activation.

All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies thus confirming the activity of the S9-mix and the sensitivity of the bacterial strains.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
negative

The test material was considered to be non-mutagenic under the conditions of this test.

Executive summary:

Introduction.

The method was designed to conform to the guidelines for bacterial mutagenicity testing published by the major Japanese Regulatory Authorities including METI, MHLW and MAFF. It also meets the requirements of the OECD Guidelines for Testing of Chemicals No. 471 "Bacterial Reverse Mutation Test", Method B13/14 of Commission Directive 2000/32/EC and the, EPA (TSCA) OPPTS harmonised guidelines.

Methods.

Salmonella typhimuriumstrains TA1535, TA1537, TA98 and TA100 andEscherichia colistrain WP2uvrA^-were treated with the test material using the Ames plate incorporation method at five dose levels, in triplicate, both with and without the addition of a rat liver homogenate metabolising system (10% liver S9 in standard co-factors). The dose range for the range-finding test was determined in a preliminary toxicity assay and was 50 to 5000 µg/plate. The experiment was repeated on a separate day using the same dose range as the range-finding test, fresh cultures of the bacterial strains and fresh test material formulations.

Results.

The vehicle (sterile distilled water) control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with or without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

The test material caused no visible reduction in the growth of the bacterial background lawn at any dose level. The test material was, therefore, tested up to the maximum recommended dose level of 5000 µg/plate. No test material precipitate was observed on the plates at any of the doses tested in either the presence or absence of S9-mix.

No significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation.

Conclusion. The test material was considered to be non-mutagenic under the conditions of this test.