Carvacrol-rich essential oil obtained from the leaves of Origanum spp., Labiatae, by distillation

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 March 2018 - 11 June 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

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)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Carvacrol-rich essential oil obtained from the leaves of Origanum spp., Labiatae, by distillation

EC Number:

947-697-6

Molecular formula:

Not relevant, UVCB substance

IUPAC Name:

Carvacrol-rich essential oil obtained from the leaves of Origanum spp., Labiatae, by distillation

Test material form:

liquid

Details on test material:

Manufacturing date: 17/08/2017
Expiry date: 17/08/2018

Method

Target gene:

Histidine and tryptophan

Species / strain

Species / strain / cell type:

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

Metabolic activation:

with and without

Metabolic activation system:

S9 fraction, microsome fraction prepared from Sprague Dawley rat liver homogenate, is provided by MOLTOXTM

Test concentrations with justification for top dose:

Test for Mutagenicity (Experiment 1) – Plate Incorporation Method:
Salmonella strains TA 98, TA 100, TA 1535, TA 1537 and E. coli WP2uvrA (with and without S9 mix): 15, 45, 150, 450 and 1500 μg/plate

Test for Mutagenicity (Experiment 2) :
Salmonella strains TA 98, TA 100, TA 1535, TA 1537 and E. coli WP2uvrA (with and without S9 mix): 15, 45, 150, 450 and 1500 μg/plate

Vehicle / solvent:

DMSO

Controls

Controls 1

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

7,12-dimethylbenzanthracene

9-aminoacridine

sodium azide

Controls 2

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

other: cis-Platinum (II) Diammine Dichloride (1 µg/plate E. coli - S9), 2-Nitrofluorene (2 µg/plate, TA98 - S9) and 2-Anthramine (2 µg/plate, TA strains + S9)

Details on test system and experimental conditions:

SOURCE OF TEST SYSTEM:
Strains of Salmonella typhimurium and Escherichia coli are purchased from MOLTOX

METHOD OF APPLICATION: in agar (plate incorporation); preincubation

DURATION
- Preincubation period:
37 °C for 30 minutes (with shaking)
- Exposure duration:
Plates were incubated at 37 °C ± 3 °C for approximately 48-72 hours


NUMBER OF REPLICATIONS:
Triplicate plates per dose level.

DETERMINATION OF CYTOTOXICITY
- Method: The plates were viewed microscopically for evidence of thinning (toxicity)

Rationale for test conditions:

The highest dose tested was 1 500 μg/plate.

Evaluation criteria:

Ensure that the criteria of validity of the study are well respected namely
 There should be a mimimum of four non-toxic test item dose levels
 the bacteriostatic activity of the highest concentration tested shall be equal to or less than 75 %.
 The spontaneous reversion rate of the absolute negative control shall comply with the historical values of the laboratory,
 the spontaneous reversion rate of the solvent shall not be statistically different from absolute negative control,
 the mean number of revertant colonies obtained for each strain and the corresponding positive control, with and/or without metabolic activation shall comply with the historical values of the laboratory.
 Negative and positive values should not show significant difference with the historical values of the laboratory (± 2 standard deviations).

Results and discussion

Test results

Test results 1

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 3

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 4

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 5

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

STERILITY CONTROLS:
absence of any bacterial growth in the presence of the various concentrations of the test item.
absence of any bacterial growth in the presence of "S9-mix".

BACTERIOSTATIC ACTIVITY CONTROL:
Results show a high toxicity from 1500 to 5000 μg/plate in TA 100. Therefore the test item is tested at these doses (1500, 450, 150, 450 and 15 μg/plate).

MUTATION ASSAY
- There is no significant difference between the number of spontaneous reversions, the number of reversions obtained for the positive controls (without and with metabolic activation), and the mean of corresponding experimental historical values obtained in the laboratory.
- There is no evidence of any increase in the number of revertant colonies in the presence and absence of metabolic activation in S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and in E. coli WP2(uvrA-) (pKM101) at any dose tested with the test item up to cytotoxic concentrations.
- One can observe a thinning of the bacterial lawn in the presence of the highest doses 1500 and 450 µg/plate, correlated with the toxicity measured.
- Results are confirmed in an independent experiment.

Applicant's summary and conclusion

Conclusions:

There is no evidence of any increase in the number of revertant colonies in the presence and absence of metabolic activation in S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and in E. coli WP2(uvrA-) (pKM101) at any dose tested with the test item up to cytotoxic concentrations.

Executive summary:

The test item was tested for it capacity to induce reverse mutation in four Salmonella typhimurium strains and one Escherichia coli WP2(uvr A¯) (pKM101) strain. This study was performed in the absence and presence of metabolic activation. Two independent assays were carried out.

For assay n° 1, various concentrations (from 15 to 1500 µg/plate) of test item in DMSO were put in contact with the strains in the absence and presence of a metabolic activation system (S9-mix 10% (v/v)).

For assay n° 2, various concentrations (from 15 to 1500 µg/plate) of test item in DMSO were put in contact with the strains in the absence of metabolic activation and with pre-incubation in the presence of metabolic activation system (S9-mix 10% (v/v)).

For the two assays, negative and positive controls were carried out in parallel. Positive controls induced a significant increase in the number of revertant colonies compared to negative controls. There is no significant difference between the number of spontaneous reversions, the number of reversions obtained in the positive controls (without and with metabolic activation), and the mean of corresponding experimental “historical” values obtained in the laboratory.

There is no evidence of any increase in the number of revertant colonies in the presence and absence of metabolic activation in S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and in E. coli WP2(uvrA-) (pKM101) at any dose tested with the test item up to cytotoxic concentrations.