Propanoic acid, 2-(4-hydroxyphenoxy)-, potassium salt (1:1), (2R)-

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

1995-08-10 to 1995-10-04

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP study on structural analogue (free acid) according to OECD guideline. The fact that the study is used for read-across purposes triggers reliability rating 2.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1995

Report date:

1995

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OTS 798.5265 (The Salmonella typhimurium Bacterial Reverse Mutation Test)

Deviations:

no

Test guideline 4

Qualifier:

according to guideline

Guideline:

JAPAN: Guidelines for Screening Mutagenicity Testing Of Chemicals

Deviations:

no

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

(R)-2-(4-Hydroxyphenoxy)propanoic acid

IUPAC Name:

(R)-2-(4-Hydroxyphenoxy)propanoic acid

Constituent 2

Reference substance name:

Propanoic acid, 2-(4-hydroxyphenoxy)-, (2R)-

IUPAC Name:

Propanoic acid, 2-(4-hydroxyphenoxy)-, (2R)-

Constituent 3

Reference substance name:

94050-90-5

Cas Number:

94050-90-5

IUPAC Name:

94050-90-5

Constituent 4

Reference substance name:

(R)-2-(4-hydroxyphenoxy)propanoic acid

EC Number:

407-960-3

EC Name:

(R)-2-(4-hydroxyphenoxy)propanoic acid

IUPAC Name:

407-960-3

Details on test material:

- Substance type: Pure test substance
- Physical state: Solid

Method

Target gene:

hisD, hisG, hisC, trpE

Species / strain

Species / strain 1

Species / strain / cell type:

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

Species / strain 2

Species / strain / cell type:

S. typhimurium TA 102

Species / strain 3

Species / strain / cell type:

E. coli WP2 uvr A

Metabolic activation:

with and without

Metabolic activation system:

Rat liver S9 fraction, induced with Aroclor 1254

Test concentrations with justification for top dose:

Range finding test: 20.6, 61.7, 185, 556, 1667, 5000 microgram/plate (with S. typhimurium TA100 and E. coli WP2 uvrA only)
Main experiment: 312.5, 625, 1250, 2500, 5000 microgram/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: solubility of test substance without precipitation

Controls

Controls 1

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

without metabolic activation

4-nitroquinoline, mitomycin-C, 2-nitrofluorene, 9-aminoacridine

Controls 2

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

with metabolic activation for TA1535, 2-aminoanthracene for all other strains

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Incubation period: 48 hours at 37 +/- 1.5°C

NUMBER OF REPLICATIONS: 3
- Two identical replicate experiments with identical concentrations: original and confirmatory

DETERMINATION OF CYTOTOXICITY
- Method: inspection of the bacterial background lawn, reduction of revertant colony numbers

Evaluation criteria:

Criteria for positive response:
- Reproducible doubling of mean number of revertants above solvent control (at any concentration): for S. typhimurium TA98, TA1535, TA1537, E. coli WP2 uvrA
- Reproducible increase of mean number of revertants by at least a factor 1.5 above solvent control (at any concentration): for S. typhimurium TA100, TA102
- Concentration-related effect should be demonstrable

Assay acceptance criteria:
- Mean colony counts of negative control of all strains within acceptable range (historical controls documented)
- Results for positive controls meet criteria for positive response (historical controls documented)

Statistics:

None

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:

not applicable

Positive controls validity:

valid

Test results 2

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:

not applicable

Positive controls validity:

valid

Test results 3

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:

not applicable

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- precipitation: none
- no reduction of the background lawn

RANGE-FINDING/SCREENING STUDIES:
- no increase in colony counts
- no signs of strong cytotoxicity (no reduction of the background lawn)
- slight reduction of revertant colony numbers at highest concentration, E. coli with S) only

ANALYTICAL DETERMINATION OF TEST SUBSTANCE
- HPLC with UV detection
- lowest serial dilution of stock solution in DMSO analyzed (in duplicate)
- recoveries 97.2 % and 100.8%
- test substance stable in the vehicle

Remarks on result:

other: all strains/cell types tested

Any other information on results incl. tables

No increase in the incidence of either histidine- or tryptophan-prototrophic mutants was elicited by the source substance, the free acid (R)-2-(4-hydroxyphenoxy)-propanoic acid (CAS 94050-90-5), in strains S. typhimurium TA 98, TA 100, TA 102, TA1535, TA1537 and E. coli WP2 uvrA, with and without metabolic activation, i.e. the source substance and its metabolites did not induce gene mutations.

The bacterial mutagenicity of the target substance propanoic acid, 2-(4-hydroxyphenoxy)-, potassium salt (2R) (CAS 1184648-08-5) is determined by read-across from the Ames test with the free acid. The analogue approach is based on the facts that source and target contain the identical molecular structure and the same functional groups (except the K+ counterion), and that they form a pH-dependent equilibrium. In the assay mixture (top agar), the free acid is neutralized to the Na+ salt (by the buffer, with a possible pH decrease to 6.4), whereas the K+ counterion of the salt would be exchanged to Na+ (due to the sodium excess), which makes the two forms indistinguishable. Potassium (in the form of KCl) has been shown to cause no increase in mutation frequencies.

No mutagenic effect was observed with the free acid. As a conclusion, the target substance propanoic acid, 2-(4-hydroxyphenoxy)-, potassium salt (2R) is also unlikely to be a bacterial mutagen in the Ames test.

Applicant's summary and conclusion

Conclusions:

Interpretation of results: negative

Potassium (R)-2-(4-hydroxy-phenoxy)-propionate is unlikely to be a bacterial mutagen in the Ames test based on read-across.