5-(dithiolan-3-yl)valeric acid

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in chemico

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-12-29 - 2017-05-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 442C (In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA))

Version / remarks:

2015-02-04

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

direct peptide reactivity assay (DPRA)

Justification for non-LLNA method:

According to REACH regulation Annex VII, 8.3.2 column 2 an in vivo test (LNNA is preferred) will only be performed, when the in chemico / in vitro
methods according to 8.3.1, column 1 are not applicable for the test substance or the are not convincing.

The correlation of protein reactivity with skin sensitisation potential of a chemical is well established and represents the first and initial key event in the skin sensitisation process as defined by the AOP. It is therefore a crucial step for the sensitising potential of a chemical.

This test method is able to detect chemicals that cause skin sensitisation and allows for hazard identification in accordance with UN GHS “Category 1”.

Test material

Test material information

Constituent 1

Reference substance name:

5-(dithiolan-3-yl)valeric acid

EC Number:

214-071-2

EC Name:

5-(dithiolan-3-yl)valeric acid

Cas Number:

1077-28-7

Molecular formula:

C8H14O2S2

IUPAC Name:

5-(1,2-dithiolan-3-yl)pentanoic acid

impurity 1

Reference substance name:

unknown

IUPAC Name:

unknown

impurity 2

Reference substance name:

Water

EC Number:

231-791-2

EC Name:

Water

Cas Number:

7732-18-5

Molecular formula:

H2O

IUPAC Name:

dihydrogen oxide

Test material form:

solid: bulk

Details on test material:

This composition is the usual techical grade of AlzChem AG. It will be used when test substance has this composition (or is very closed) or no specific information is available

Results and discussion

Positive control results:

Mean Peptide depletion: 73.04 %

In vitro / in chemico

Results

Results 1

Key result

Parameter:

cysteine depletion

Value:

20.62 %

At concentration:

0.392 mM

Vehicle controls validity:

not examined

Remarks:

Acetonitrile

Negative controls validity:

valid

Positive controls validity:

valid

Remarks:

Cinnamic aldehyde

Results 2

Key result

Parameter:

lysine depletion

Value:

1.31 %

At concentration:

0.501 mM

Vehicle controls validity:

not examined

Remarks:

Acetoitrile

Negative controls validity:

valid

Positive controls validity:

valid

Remarks:

Cinnamic aldihyde

Applicant's summary and conclusion

Interpretation of results:

Category 1 (skin sensitising) based on GHS criteria

Conclusions:

In this study under the given conditions the test item showed low reactivity towards the peptides. The test item can be classified as “sensitiser” in accordance with UN GHS “Category 1”.
The data generated with this method may be not sufficient to conclude on the skin sensitisation potential of chemicals and should be considered in the context of integrated approach such as IATA.

Executive summary:

The in chemico direct peptide reactivity assay (DPRA) enables detection of the sensitising potential of a test item by quantifying the reactivity of test chemicals towards synthetic peptides containing either lysine or cysteine.

In the present study Thioctic Acid was dissolved in acetonitrile. Based on a molecular weight of 206.3 g/mol a 100 mM stock solution was prepared. The test item solutions were tested by incubating the samples with the peptides containing either cysteine or lysine for 24 ± 2 h at 25 ± 2.5 °C. Subsequently samples were analysed by HPLC.

After the 24 h ± 2 h incubation period but prior to the HPLC analysis samples of the cysteine and lysine peptide run were inspected for precipitation, turbidity or phase separation. A slight precipitation was observed for the test item samples and the samples of the positive control. Samples were not centrifuged prior to the HPLC analysis.

After the 24 h ± 2 h incubation period but prior to the HPLC analysis samples of the lysine peptide run were inspected for precipitation, turbidity or phase separation. Turbidity and phase separation was observed for the samples of the positive control and the respective co-elution control. Samples were not centrifuged prior to the HPLC analysis.

Since the positive control was fulfilled the validity criteria in both experiments the precipitation, turbidity and phase separation was considered as irrelevant.

No co-elution of test item with the peptide peaks was observed. Sensitizing potential of the test item was predicted from the mean peptide depletion of both analysed peptides (cysteine and lysine) by comparing the peptide concentration of the test item treated samples to the corresponding reference control C (RC C).

The 100 mM stock solution of the test item showed low reactivity towards the synthetic peptides. The mean depletion of both peptides was > 6.38% (10.96%). Based on the prediction model 1 the test item can be considered to possess sensitising potential. Due to the observed precipitation in the test item samples of the cysteine peptide experiment the reactivity might be underestimated.

The 100 mM stock solution of the positive control (cinnamic aldehyde) showed high reactivity towards the synthetic peptides. The mean depletion of both peptides was 62.33%.