Octyl (R)-2-(4-chloro-2-methylphenoxy)propionate

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP and guideline study (OECD TG 471)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

(1997)

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Octyl (R)-2-(4-chloro-2-methylphenoxy)propionate

EC Number:

266-358-7

EC Name:

Octyl (R)-2-(4-chloro-2-methylphenoxy)propionate

Cas Number:

66423-13-0

Molecular formula:

C18H27ClO3

IUPAC Name:

octyl (2R)-2-(4-chloro-2-methylphenoxy)propanoate

Constituent 2

Reference substance name:

Mecoprop-P n-octyl ester

IUPAC Name:

Mecoprop-P n-octyl ester

Constituent 3

Reference substance name:

Preventol B5

IUPAC Name:

Preventol B5

Constituent 4

Reference substance name:

R-(+)-2-(4-chloro-2-methylphenoxy)-propionic acid, octyl ester

IUPAC Name:

R-(+)-2-(4-chloro-2-methylphenoxy)-propionic acid, octyl ester

Details on test material:

- Stability under test conditions: A stability test in the solvent did not reveal significant degradation of the active ingredient.

Method

Target gene:

mutant histidine gene

Species / strain

Species / strain / cell type:

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

Metabolic activation:

with and without

Metabolic activation system:

S9-Mix from the liver of Aroclor 1254 induced male Sprague Dawley rats.

Test concentrations with justification for top dose:

plate incorporation assay: 0, 50, 158, 500, 1581, 5000 µg/plate with and without S9 mix
preincubation assay: 0, 50, 158, 500, 1581, 5000 µg/tube with and without S9 mix

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: The test item formed clear colorless solutions in DMSO.

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: Sodium azide (TA 1535), nitrofurantoin (TA100), 4-nitro-1,2-phenylene diamine (TA 1535 and TA 98), mitomycin C (TA 102), cumene hydroperoxide (TA102), 2-aminoanthracene (all tester strains with S9 mix)

Remarks:

The positive controls sodium azide, nitrofurantoin, 4-nitro-1,2-phenylene diamine, mitomycin C and cumene hydroperoxide were only used without S9 mix; the positive control 2-aminoanthracene was only used with S9 mix.

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation) for initial testing, following the directions of Maron and Ames (Mutation Res. 113, 1983, 173-215); independent repeat as preincubation testing (preincubation for 20 min. at 37°C);
Testing for each strain and dose with and without S9 mix was performed in triplicate, which is also valid for solvent and positive controls.

DETERMINATION OF CYTOTOXICITY
- background growth
- mutant count: A toxic effect was assumed when there was a marked and dose-dependent reduction in the mutant count per plate, compared to the negative controls.

Evaluation criteria:

A reproducible and dose-related increase in mutant counts of at least one strain is considered to be a positive result. For TA 1535, TA 100, TA 1537and TA 98 this increase should be about twice that of negative/solvent controls. For TA 102 an increase of about 100 mutants should be reached. Otherwise, the result is evaluated as negative. However, these guidelines may be overruled by good scientific judgment.

Results and discussion

Test results

Species / strain:

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

Additional information on results:

None of the five strains used showed a dose-related and biologically relevant increase in mutant counts over those of the negative controls. This applied both to the tests with and without S9 mix.

TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: Precipitation was indicated at the highest dose evaluated (5000 µg/plate)

ADDITIONAL INFORMATION ON CYTOTOXICITY: Doses up to and including 5000 µg per plate did not cause any bacteriotoxic effects. Total bacteria counts remained unchanged and no inhibition of growth was observed.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

Three replicates per dose and tester strain with and without metabolic activation (n = 3)

1st experiment plate incorporation test (without metabolic activation)

Summary of mean values without S9 mix in the plate incorporation test
	Strain
Dose µg/plate	TA1535	TA100	TA1537	TA98	TA102
0	9 ± 1	95 ± 10	8 ± 2	22 ± 2	270 ± 11
50	10 ± 1	93 ± 14	8 ± 3	18 ± 3	249 ± 20
158	8 ± 1	105 ± 7	8 ± 1	21 ± 3	240 ± 33
500	7 ± 1	83 ± 7	7 ± 1	21 ± 3	236 ± 12
1581	9 ± 2	92 ± 22	8 ± 1	21 ± 2	247 ± 17
5000	9 ± 2	98 ± 22	8 ± 1	23 ± 1	249 ± 8
Na-azide	710 ± 45
NF		311 ± 16
4 -NPDA			34 ± 1	78 ± 4
MMC					692 ± 34

1st experiment plate incorporation test (with metabolic activation)

Summary of mean values with S9 mix in the plate incorporation test
	Strain
Dose µg/plate	TA1535	TA100	TA1537	TA98	TA102
0	11  ± 2	131  ±	10  ± 3	36  ± 3	363  ± 8
50	11  ± 4	129  ±	10  ± 2	31  ± 10	373  ± 8
158	12  ± 2	133  ±	10  ± 2	30  ± 5	375  ± 17
500	10  ± 3	128  ±	9 ± 3	29  ± 6	384  ± 35
1581	10  ± 2	115  ±	10 ± 2	29  ± 5	374  ± 6
5000	10  ± 1	109  ±	9  ± 1	31  ± 4	396  ± 28
2 -AA	135  ± 2	2404  ±	216  ± 31	2131  ± 393	830  ± 97

2nd experiment pre-incubation method (without metabolic activation)

Summary of mean values without S9 mix in the pre-incubation method
	Strain
Dose µg/plate	TA1535	TA100	TA1537	TA98	TA102
0	8  ± 1	131 ± 6	7  ± 1	20  ± 4	251  ± 11
50	9  ± 2	115 ± 29	7  ± 1	22  ± 3	252  ± 7
158	9  ± 2	127 ± 29	8  ± 2	17  ± 4	235  ± 31
500	9  ± 2	124 ± 8	8  ± 2	16  ± 1	249  ± 32
1581	8  ± 2	130 ± 17	6  ± 1	15  ± 3	245  ± 14
5000	9  ± 3	129 ± 19	8  ± 2	20  ± 3	262  ± 27
Na-azide	872  ± 31
NF		463 ± 49
4 -NPDA			37  ± 4	71  ± 2
Cumene					508  ± 16

2nd experiment pre-incubation method (with metabolic activation)

Summary of mean values with S9 mix in the pre-incubation method
	Strain
Dose µg/plate	TA1535	TA100	TA1537	TA98	TA102
0	12  ± 3	216  ± 11	10 ± 1	32 ± 5	318  ± 12
50	13  ± 3	205  ± 21	9 ± 2	30 ± 5	298  ± 44
158	10  ± 2	187  ± 15	10 ± 1	31 ± 3	293  ± 25
500	10  ± 1	190  ± 15	8 ± 1	26 ± 4	324  ± 37
1581	10  ± 3	167  ± 2	10 ± 2	28 ± 3	334  ± 32
5000	11  ± 1	185  ± 8	9  ± 1	26 ± 4	318  ± 36
2-AA	113  ± 8	1870  ± 139	288  ± 23	1633 ± 223	521  ± 13

Applicant's summary and conclusion

Executive summary:

Mecoprop-P n-octyl ester was investigated in a bacterial reverse mutation (Ames) test according to OECD TG 471 on Salmonella typhimurium TA 1535, TA 100, TA, 1537, TA 98, and TA 102. Cytotoxicity was not indicated up to 5000 µg/plate. Precipitation of the test substance was noted at 5000 µg/plate.

None of the five strains showed a dose-related and biologically relevant increase in mutant counts over those of the negative controls in the initially performed plate incorporation as well as in the independently performed preincubation modification, each conducted with and without S9 mix.

Therefore, Mecoprop-P n-octyl ester was considered to be non-mutagenic.