(R)-5-isopropyl-2-methylcyclohexa-1,3-diene

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-05-18 to 2016-06-20

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

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Version / remarks:

July 28, 2015

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Version / remarks:

REACH; 1st ATP 2009: EC Regulation No 761/2009 of 23 July 2009 amending, for the purpose of its ATP, EC Regulation No 440/2008 laying down test methods

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: UN GHS (published 2003, last (6th) revision 2015)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

(R)-5-isopropyl-2-methylcyclohexa-1,3-diene

EC Number:

224-167-6

EC Name:

(R)-5-isopropyl-2-methylcyclohexa-1,3-diene

Cas Number:

4221-98-1

Molecular formula:

C10H16

IUPAC Name:

(5R)-2-methyl-5-(propan-2-yl)cyclohexa-1,3-diene

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Justification for test system used:

In an international prevalidation study performed by ECVAM, the in vitro skin irritation test using the human skin model EpiDerm™ and EpiSkin™ and measurement of cell viability by dehydrogenase conversion of MTT into a blue formazan salt have turned out as a sufficiently promising predictor for skin irritancy potential.

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: human skin model EpiDerm™
- Tissue batch number: 23341
- Delivery date: 14 June 2016
- Date of initiation of testing: 14 June 2016 (preincubation phase)

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 37 ± 1.5 °C, 5 ± 0.5% CO2
- Temperature of post-treatment incubation: 37 ± 1.5 °C, 5 ± 0.5 % CO2

REMOVAL OF TEST MATERIAL AND CONTROLS
- Volume and number of washing steps: Rinsed with DPBS at least 15 times, after the rinsing the inserts were submerged in DPBS at least three times. Afterwards the inserts were once again rinsed with sterile DPBS from the inside and the outside.
- Observable damage in the tissue due to washing: No
- Modifications to validated SOP: No

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: (1 mg/mL)
- Incubation time: 3 hours
- Spectrophotometer: Versamax® Molecular Devices, Softmax Pro, version 4.7.1
- Wavelength: 570 nm
- Filter: 570 nm

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: Positive: 4.64%, range 4.00 - 5.90 %

NUMBER OF REPLICATE TISSUES: 3

CONTROL TISSUES USED IN CASE OF MTT DIRECT INTERFERENCE
Since the MTT solution did not turn blue/purple, the test item was not considered to reduce MTT and an additional test with freeze-killed tissues did not have to be performed.

NUMBER OF INDEPENDENT TEST SEQUENCES / EXPERIMENTS TO DERIVE FINAL PREDICTION: 1

PREDICTION MODEL / DECISION CRITERIA
- The test substance is considered to be irritant to skin if the mean tissue viability is ≤ 50 %.
- The test substance is considered to be non-irritant to skin if the mean tissue viability is > 50 %

Acceptability of the Assay
Criterion 1
Negative control: The absolute OD 570 nm of the negative control tissues in the MTT test is an indicator of tissue viability obtained after the shipping and storing procedure and under specific conditions of the assay. Tissue viability is meeting the acceptance criterion if the mean OD570 of the negative control tissues is ≥ 0.8 and ≤ 2.8.

Criterion 2
Positive control: An assay is meeting the acceptance criterion if mean relative tissue viability of the positive control is ≤ 20%.

Criterion 3
Standard deviation: The SD of 3 identical replicates should be < 18%. OD values should not be below historically established boundaries.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount applied: 30 μL (47 μL/cm2)
- Concentration: undiluted

NEGATIVE CONTROL
- Amount applied : 30 μL DPBS (MatTek)

POSITIVE CONTROL
- Amount applied: 30 μL
- Concentration: 5% SLS solution in deionised water

Duration of treatment / exposure:

1 hour

Duration of post-treatment incubation (if applicable):

42.75 hours

Number of replicates:

3

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

mean of 3 tissues

Value:

94.2

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Remarks:

100 % viability

Positive controls validity:

valid

Remarks:

4.5 % viability

Other effects / acceptance of results:

- Direct-MTT reduction: test item did not reduce MTT
- Colour interference with MTT: test item did not change colour in the colour interference test
- After treatment with the negative control the absorbance values were well in the required range of the acceptability criterion of mean OD = 0.8 and = 2.8 for the 60 minutes treatment interval, thus assuring the quality of the tissues.
- Treatment with the positive control induced a sufficient decrease in the relative absorbance as compared to the negative control for the 60 minutes treatment interval, and thus assuring the validity of the test system; the mean relative absorbance value of the positive control was 4.5% compared to the negative control.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

The test item was determined to be not irritant to skin in the in vitro Human Skin Model Test.

Executive summary:

This in vitro study was performed to assess the irritation potential of the test item by means of the Human Skin Model Test.

The test item did not reduce MTT (test for direct MTT reduction), and it did not change colour when mixed with deionised water (test for colour interference). Also its intrinsic colour was not intensive.

Consequently, additional tests with freeze-killed or viable tissues were not necessary. Each three tissues of the human skin model EpiDerm™ were treated with the test item, the negative or the positive control for 60 minutes.

30 μL of the test item were applied to each tissue, and spread to match the surface of the tissue. Furthermore, 30 μL of either the negative control (DPBS) or the positive control (5% SLS) were applied to each tissue. After treatment with the negative control the absorbance values were well within the required range of the acceptability criterion of mean OD≥0.8 and≤2.8 for the 60 minutes treatment interval, thus assuring the quality of the tissues.

Treatment with the positive control induced a sufficient decrease in the relative absorbance as compared to the negative control for the 60 minutes treatment interval, and thus assuring the validity of the test system.

After treatment with the test item the mean relative absorbance value decreased irrelevantly to 94.2% compared to the relative absorbance value of the negative control. This value is above the threshold for irritancy of≤50%. Therefore, the test item is not considered to possess an irritant potential.

In conclusion, it can be stated that in this study and under the experimental conditions reported, the test item is not irritant to skin.