Dibenzyl sulphoxide

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:

22.01.2016 – 24.03.2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Council Regulation (EC) No.440/2008. Published in O.J. L 142, 2008

Deviations:

yes

Remarks:

(see Any other information ...)

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Dibenzyl sulphoxide

EC Number:

210-668-7

EC Name:

Dibenzyl sulphoxide

Cas Number:

621-08-9

Molecular formula:

C14H14OS

IUPAC Name:

(phenylmethanesulfinylmethyl)benzene

Test material form:

solid: particulate/powder

Details on test material:

- State of aggregation:
- Particle size distribution:
- Mass median aerodynamic diameter (MMAD):
- Geometric standard deviation (GSD):
- Shape of particles:
- Surface area of particles:
- Crystal structure:
- Coating:
- Surface properties:
- Density:
- Moisture content:
- Residual solvent:
- Activation:
- Stabilisation:
- Other:

White solid powder
Storage: The test substance was stored in dry room in dark in closed container at the room temperature.
Content of water: 0.025 % w/w (volumetric Karl Fischer titration)

Method

Target gene:

gene for histidine or tryptophan synthesis

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:

E. coli WP2 uvr A

Metabolic activation:

with and without

Metabolic activation system:

supernatant of rat liver and a mixture of cofactors

Test concentrations with justification for top dose:

15, 50, 150, 500, 1500, 5000 μg
Selection of doses/toxicity:
The test substance was dissolved in dimethyl sulfoxide till the maximum recommended dose 5000 µg/0.1 mL. Dissolving was performed at 37±1°C for approximately 30 minutes.
For toxicity experiment, the starting solution (5000 µg/0.1 mL) was diluted to concentration series 10 - 5000 µg per plate. The concentration row was tested for toxicity in strain TA 98 without metabolic activation.
Precipitation in top agar was observed in the dose of 5000 µg per plate where decrease of number of revertants was observed in the same time. Nevertheless, the dose of 5000 µg per plate was then used as maximum for the first mutagenicity experiments. The maximum dose was diluted according to the rules given in guidelines. The doses used were 50, 150, 500, 1500 and 5000 µg per plate.
In the first experiments some toxicity (decreased number of revertants, diminution of bacterial background or both) was observed in some bacterial strains. Evaluation was also somewhat difficult because of particles of the test substance in background in the highest concentration. Therefore, maximum dose was reduced to 1500 µg per plate for the second mutagenicity experiments.
Fresh solutions of the test substance were prepared before each experiment. All concentrations of the test substance solution were dosed in the volume of 0.1 mL per plate.

Vehicle / solvent:

Dimethylsulfoxide, Merck, Lot No. K 46505352516, exp. 03/2018
- Justification for choice of solvent/vehicle: solubility of the substance


Controls
Each experiment included corresponding positive (reference mutagens) and negative controls (untreated control, solvent control). Untreated controls contain no solvent; negative controls contain 0.1 mL of DMSO for injection. All the control numbers were compared with historical ranges of mutant frequencies obtained in our laboratory. The actual numbers were in ranges of the historical numbers.

Controls

Controls 1

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

(AS)

Controls 2

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

sodium azide

other: N-methyl-N´-nitro-N-nitrosoguanidine; 4-nitro-o-phenylenediamine; 2-aminofluorene; 2-aminoanthracene;

Remarks:

(other: MNNG; NPD; AF; 2-AA)

Details on test system and experimental conditions:

The bacterial tester strains Salmonella typhimurium TA 1535 (CCM 3814, lot. No. 2101200916917), TA 98 (CCM 3811, lot No. 01022001220053), TA 100 (CCM 3812, lot No. 0102201220054) and TA 1537 (CCM 3815, lot No. 2101200916918) as well as Escherichia coli WP2 uvrA (CCM 4751, lot No. 2104200512732), - were obtained from Czech Collection of Microorganisms (CCM) of Masaryk University, Brno.
Strains TA 98 and TA 1537 detect frame shift mutations, strains TA 100 and TA 1535 serve to detection of base-pair substitution mutations, and strain E.coli WP2 uvrA detects cross-linking mutagens.

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

NUMBER OF REPLICATIONS: two series

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth

Evaluation criteria:

The main criterion for evaluation of results was modified two-fold increase rule, which is compatible with the application of statistical methods (below). After this rule the result is positive, if a reproducible doseresponse effect occurs and/or a doubling of the ratio Rt/Rc is reached.

Statistics:

For the evaluation of results, the modified two-fold increase rule was used, which is compatible with the application of statistical methods:
Dunkel V. C.. Chu K.C. (1980): Evaluation of methods for analysis of microbial mutagenicity assays in The Predictive Value of Short-Term Screening Tests in Carcinogenicity Evaluation. Elsevier North-Holland Biomedical Press. 231 - 417
Claxton L. D. et al. (1987): Guide for the Salmonella typhimurium/mammalian microsome tests for bacterial mutagenicity. Mutat. Res. 189. 83 - 91

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:

not determined

Vehicle controls validity:

valid

Untreated negative 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:

not determined

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 3

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 4

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Test results 5

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 6

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

HISTORICAL CONTROL DATA:
Each experiment included corresponding positive (reference mutagens) and negative controls (untreated control, solvent control). Untreated controls contain no solvent and negative controls contain 0.1 mL DMSO. All the control numbers were compared with historical ranges of mutant frequencies obtained in our laboratory. The actual numbers were in ranges of the historical numbers.

ADDITIONAL INFORMATION ON CYTOTOXICITY:
For toxicity experiment, the starting solution (5000 µg/0.1 mL) was diluted to concentration series 10 - 5000 µg per plate. The concentration row was tested for toxicity in strain TA 98 without metabolic activation.
Precipitation in top agar was observed in the dose of 5000 µg per plate where decrease of number of revertants was observed in the same time. Nevertheless, the dose of 5000 µg per plate was then used as maximum for the first mutagenicity experiments. The maximum dose was diluted according to the rules given in guidelines. The doses used were 50, 150, 500, 1500 and 5000 µg per plate.
In the first experiments some toxicity (decreased number of revertants, diminution of bacterial background or both) was observed in some bacterial strains. Evaluation was also somewhat difficult because of particles of the test substance in background in the highest concentration. Therefore, maximum dose was reduced to 1500 µg per plate for the second mutagenicity experiments.
Fresh solutions of the test substance were prepared before each experiment. All concentrations of the test substance solution were dosed in the volume of 0.1 mL per plate.

Applicant's summary and conclusion

Conclusions:

Under the above-described experimental design, the test substance, Dibenzylsulfoxide, was nonmutagenic for all the Salmonella typhimurium as well as Escherichia coli strains with as well as without metabolic activation.

Executive summary:

The test substance Dibenzylsulfoxide was assayed for the mutagenicity by the Bacterial Reverse Mutation Test. The performed test was based on EU method B.13/14 Mutagenicity – Reverse mutation test using bacteria, which is analogous to the OECD Test Guideline No. 471.

Four indicator Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA 1537 and one indicator Escherichia coli WP2 uvrA strain were used. The test substance was dissolved in dimethyl sulfoxide (DMSO) and assayed in doses of 10-5000 ug per plate, which were applied to plates in volume of 0.1 mL.

Experiments were performed without as well as with metabolic activation with a supernatant of rat liver and a mixture of cofactors.

In the arrangement given above, the test substance, Dibenzylsulfoxide, was non-mutagenic for all the used tester strains without as well as with metabolic activation.