2-Hexadecen-1-ol, 3,7,11,15-tetramethyl-

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in chemico

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Type of study:

direct peptide reactivity assay (DPRA)

Test material

Test material information

Constituent 1

Reference substance name:

3,7,11,15-tetramethylhexadec-2-en-1-ol

EC Number:

616-221-6

Cas Number:

7541-49-3

Molecular formula:

C20H40O

IUPAC Name:

3,7,11,15-tetramethylhexadec-2-en-1-ol

Specific details on test material used for the study:

Test Item
Designation in Test Facility: 20061504G
Date of Receipt: 15. Jun. 2020
Condition at Receipt: Ambient temperature, in proper conditions

Specification
The following information concerning identity and composition of the test item was provided by the sponsor.
Name 3,7,11,15-tetramethyl-2-hexadecen-1-ol
Batch no. PL200101
CAS no. 7541-49-3
Composition 3,7,11,15-tetramethyl-2-hexadecen-1-ol 96.6 %
Storage see others
Expiry date 19. Jan. 2022
Stability stable under storage conditions
Appearance Colorless to light yellow clear oily liquid
Purity 96.6%
Homogeneity homogeneous
Production date 20. Jan. 2020
EC no. 616-221-6
Molecular formula C20H40O
Molecular weight 296.53 g/mol
Vapour pressure not stated
Solubility in solvents H2O: unknown; EtOH: not stated; acetone: not stated; CH3CN: not stated; DMSO: not stated;
Stability in solvents H2O: not stated; EtOH: not stated; acetone: not stated; CH3CN: not stated; DMSO: not stated

A certificate of analysis is provided by the sponsor and attached (in copy) in chapter 20, page 36.

Storage in Test Facility
The test item was stored in the fridge (2 - 8 °C) from 15. Jun. 2020 - 20. Oct. 2020 and stored in a closed vessel at room temperature (20 ± 5 °C) since 20. Oct. 2020. This deviation was assessed as uncritical by the sponsor.  
Preparation of test item
The concentration of the test item to be used was determined based on the molecular weight (MW) 296.53 g/mol and the purity 96.6%.

The target weight (± 10%) of the test item was calculated using this equation:

"Weight " ["mg" ]" = 3 mL×" "1 L" /"1000 mL" "×" "100 mmol" /"L" " × MW" ["mg" /"mmol" ]"×" "100" /"% Purity" "=" "MW" /"% Purity" "×30"


In a non-GLP pre-test the solubility of the test item was determined in acetonitrile (ACN) and it was sufficiently soluble.

Based on this non-GLP pre-test, the 100 mM test item solution was prepared by dissolving 92.0 mg and 92.1 mg test item in 3 mL acetonitrile for the Cys-peptide and Lys-peptide assay, respectively. The solution was vortexed until it was dissolved completely.

In chemico test system

Details on the study design:

6.2 Test system
6.2.1 Analytical instrument
Designation: HPLC_8
Components: Solvent Rack SRD3400
Quaternary pump HPG-3400SD
Autosampler WPS-3000SL
Column compartment TCC-3000SD
Photometer VWD-3400RS
Manufacturer: Thermo Fisher Scientific
Software: CHROMELEON 6.80 SR15b Build 4981
Usage and calibration followed the corresponding SOP 114 00 529, edition 2 valid from 20. Sep. 2018.

6.2.2 Column
An ACE Excel SuperC18 150 x 3 mm column with 3 µm particles and pre-column Phe-nomenex SecurityGuard C18, 4 x 3 mm was used. This column was selected because it delivers substantially better peak shape for the peptides than the Agilent Zorbax SB-C18 column recommended in the guideline OECD 442C.
6.2.3 HPLC program
Eluent A H2O + 0.1 % TFA
Eluent B Acetonitrile + 0.085 % TFA
Gradient time (min) % A % B
0 90 10
10 75 25
10.5 10 90
12 10 90
13 90 10
20 90 10
Flow rate 0.55 mL/min
Injection volume 7 µL
Column temperature 30 °C
Wavelength 1 220 nm
Wavelength 2 258 nm

 
6.2.4 Synthetic peptides
Peptides with ≥95 % purity, synthesized by RS synthesis, (Louisville, KY, USA), were used.
Cys-Peptide (Cysteine)
Sequence: Ac-RFAACAA-COOH (MW = 750.9 g/mol)
Batch no.: P190419-LC180433
Purity: 96.33%
Expiration date: 11. Dec. 2021

Lys-Peptide (Lysine)
Sequence: Ac-RFAAKAA-COOH (MW = 775.9 g/mol)
Batch no.: P170906-17-LC107617
Purity: 98.21%
Expiration date: 29. Mar. 2021

Results and discussion

Positive control results:

a) The mean peptide depletion with 70.60 % and a standard deviation of 0.10 % of the three replicates of the positive control cinnamaldehyde were in the acceptable range of 60.8 – 100.0 % and < 14.9 %, respectively, for the Cys-peptide.

In vitro / in chemico

Results

Results 1

Key result

Run / experiment:

other: In Chemico Skin Sensitisation: Direct Peptide Reac-tivity Assay (DPRA) according to OECD 442C and EU-Method B.59

Parameter:

other: Calculated peptide depletion values for the Cys-Peptide

Value:

3.51

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Remarks on result:

no indication of skin sensitisation

Results 2

Key result

Run / experiment:

other: In Chemico Skin Sensitisation: Direct Peptide Reac-tivity Assay (DPRA) according to OECD 442C and EU-Method B.59

Parameter:

other: Calculated peptide depletion values for the Lys-Peptide

Value:

0

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Remarks on result:

no indication of skin sensitisation

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

The DPRA prediction with measured values is “negative” according to the Cysteine 1:10/Lysine 1:50 prediction model based on solubilised test substance. Thus, under the experimental conditions reported, the test item 3,7,11,15-tetramethyl-2-hexadecen-1-ol shows no or minimal reactivity towards the two model synthetic pep-tides at the level of saturation in the peptide test solution. This result should, howev-er, be treated with caution.
Due to precipitation of the test item in the test solution with the Cys- and Lys-peptides, a negative conclusion should be treated with caution. The conclusion is therefore reported as being “inconclusive”.

Executive summary:

Thisin chemicostudy was performed in order to evaluate the reactivity of the test item3,7,11,15-tetramethyl-2-hexadecen-1-oltowards cysteine (Cys-) and lysine (Lys-) containing peptides.

The calculated peptide depletion could be usedto support the discrimination between skin sensitisers and non-sensitisers. The DPRA is part of a tiered strategy for the evaluation of skin sensitisation potential in the context ofan integrated approach to testing and assessment (IATA).

One valid experiment was performed.

The test item was incubated for 22 h at 25 °C together with Cys- and Lys-peptides, respectively. The peptide concentration after the incubation period was measured using HPLC-UV.

Three replicates were prepared using 1:10 and 1:50 molar ratio of the test item with the Cys- and Lys-peptides, respectively. Triplicate samples of the solvent without test item were incubated and measured simultaneously.

 

Precipitates were observed, immediately upon addition of the test item solution to the peptide solution of the Cys- and Lys-peptides. For the test item replicates with the Lys-peptides, phase separation was observed after the incubation period. This may have been caused by the low aqueous solubility of the test item.

After the incubation period, the precipitates were still present in the test item replicates with the Cys-peptides, so they were centrifuged to remove the precipitate prior to HPLC analysis. In the test item replicates with the Lys-peptides, phase separation was observed after the incubation period and only the larger peptide-phase was used for analysis.

As a consequence of the presence of precipitates, the amount of test item remaining in solution was unknown. Therefore, peptide depletion may have been underestimated and a conclusion on the lack of reactivity cannot be drawn with sufficient confidence and the study is reported as “inconclusive”.