(E,Z)-2,6-dimethylocta-2,4,6-triene

Eye irritation

Administrative data

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01-09 December 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP study performed according to OECD Guideline 492 with a minor deviation: difference of viability between negative control tissues replicates was more than the maximum acceptable variability. Considering the results obtained, this deviation was considered as without impact on the conclusion of the study.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other 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 492 (Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage)

Version / remarks:

adopted 28 July 2015

Deviations:

yes

Remarks:

difference of viability between negative control tissues replicates was more than the maximum acceptable variability

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Remarks:

2017

Test material

Test material information

Constituent 1

Reference substance name:

(E,Z)-2,6-dimethylocta-2,4,6-triene

EC Number:

230-603-6

EC Name:

(E,Z)-2,6-dimethylocta-2,4,6-triene

Cas Number:

7216-56-0

Molecular formula:

C10H16

IUPAC Name:

(E,Z)-2,6-dimethylocta-2,4,6-triene

impurity 1

Reference substance name:

(E,E)-2,6-dimethylocta-2,4,6-triene

EC Number:

221-153-1

EC Name:

(E,E)-2,6-dimethylocta-2,4,6-triene

Cas Number:

3016-19-1

Molecular formula:

C10H16

IUPAC Name:

2,6-dimethylocta-2,4,6-triene

impurity 2

Reference substance name:

(R)-p-mentha-1,8-diene

EC Number:

227-813-5

EC Name:

(R)-p-mentha-1,8-diene

Cas Number:

5989-27-5

Molecular formula:

C10H16

IUPAC Name:

(4R)-isopropenyl-1-methylcyclohexene

impurity 3

Reference substance name:

(S)-p-mentha-1,8-diene

EC Number:

227-815-6

EC Name:

(S)-p-mentha-1,8-diene

Cas Number:

5989-54-8

Molecular formula:

C10H16

IUPAC Name:

(4S)-isopropenyl-1-methylcyclohexene

impurity 4

Reference substance name:

Non identified impurities

Molecular formula:

Not applicable

IUPAC Name:

Non identified impurities

Test material form:

liquid

Details on test material:

Batch No.: 182596
Purity: 89.8%
Name of test material (as cited in study report): (E,Z)-2,6-DIMETHYLOCTA-2,4,6-TRIENE
Physical state: colourless liquid
Storage conditions: +2°C to +8°C, under nitrogen and protected from light
Expiry date: 29 December 2016

Test animals / tissue source

Species:

human

Details on test animals or tissues and environmental conditions:

- Description of the cell system used: 0.60 cm² Reconstructed human Cornea-like Epithelia [EpiOcular(TM) OCL-212-ver2.0, supplied by MatTek Corporation, batch No. 23755] were received on 07 December 2016.

Test system

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 50 µL
- Concentration (if solution): Undiluted

Duration of treatment / exposure:

30 minutes at 37°C, 5% CO2, 95% humidity (standard culture conditions)

Duration of post- treatment incubation (in vitro):

- Post-exposure immersion period: 12 minutes at room temperature
- Post-exposure incubation period: 2 hours at standard culture conditions

Number of animals or in vitro replicates:

Test item, negative and positive controls were applied on duplicate tissues.

Details on study design:

PRELIMINARY TESTS
- Test for direct interaction with MTT:
The direct interaction of MTT with the test item was checked by adding 50 µL of the test item to 1 mL of MTT solution at 1 mg/mL.
- Test for the detection of the colouring potential of the test item:
The colouration potential of the test item in isopropanol was checked by adding 50 µL of the test item to 2 mL of isopropanol.


MAIN TEST
- Pre-incubation of the tissues:
On the day of receipt, the 12 tissues in their 24-well shipping container were equilibrated at room temperature for 15 minutes. Then the inserts (filter + epithelium) were gently removed from the agarose while avoiding leaving agarose on the polycarbonate filter. They were placed in 6 wells culture plate which had been previously filled with 1 mL of 37°C pre-warmed assay medium and incubated during 19 hours and 58 minutes at standard culture conditions.
After the overnight incubation, the tissues were pre-wetted with 20 μL of Ca2+Mg2+Free-DPBS. The tissues were incubated at standard culture conditions for 30 minutes.
- Treatment and post-treatment incubation of the tissues:
The test item was applied, as supplied, at the dose of 50 µL, to the entire surface of 2 living RhCE tissue replicates during 30 minutes at standard culture conditions. In the same experimental conditions, a positive control (Methyl acetate), and a negative control (distilled water) were used. The controls were applied, as supplied, at the dose of 50 µL, to the surface of 2 viable RhCE tissue replicates during 30 minutes at standard culture conditions.
After the treatment, the test item and control substances were carefully washed from the RhCE tissues by extensive rinsing with Ca2+Mg2+Free-DPBS. The rinsed tissues were checked for any colouration and noted for comparable colour with the negative control. This rinsing step was followed by a 12-minute post-exposure immersion period at room temperature in 5 mL of fresh medium to remove any test item absorbed into the tissue. The RhCE constructs were then incubated for 2 hours post-exposure incubation at standard culture conditions in 1 mL of fresh medium at 37°C, 5% CO2.
- MTT viability assay:
Following the exposure to the test item, viability measurements are performed immediately after the post-exposure incubation period of the rinsed tissues in fresh medium. This period allows both for recovery from weak cytotoxic effects and for appearance of clear cytotoxic effects.
The RhCE tissue viability was measured by enzymatic conversion of the vital dye MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; Thiazolyl blue tetrazolium bromide; CAS No. 298-93-1] by the viable cells of the tissue into a blue MTT formazan salt that is quantitatively measured by Optical Density (OD) after extraction from tissues. The measured OD was proportional to the number of living cells.
The RhCE constructs were placed in 300 µL of a MTT solution at 1.0 mg/mL for 3 hours at standard culture conditions. The precipitated blue formazan product was then extracted from the tissues by placing each insert in 2 mL of isopropanol during 17 hours and 10 minutes at 6±3°C in the dark. The concentration of formazan was measured by determining the OD at 570 nm, just after dilution of the extractions in isopropanol (1:2). The OD measurement of formazan extracts at 570 nm was performed using the ELx800 absorbance microplate reader (controlled every year and calibrated if necessary) supplied by BioTek and the validated software Gen5 ELISA V1.05.11 supplied by BioTek.

Results and discussion

In vitro

Results

Irritation parameter:

other: % mean viability of the tissues

Run / experiment:

Main test

Value:

85.49

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

PRELIMINARY TESTS
- Test for direct interaction with MTT:
A yellow solution was observed after 3 hours of incubation between 37.8°C and 36.9°C, 5% CO2. Therefore, there is no direct interaction between the test item and MTT.
- Test for the detection of the colouring potential of the test item:
A colourless solution was obtained in isopropanol after 2 hours and 47 minutes of incubation at ambient temperature with gentle shaking. The mean of the corrected OD (blank subtracted) was 0.001 which is less than 0.08 (value corresponding to approximately twice the OD of the extracting solvent). Therefore the test item was considered to be not interfering with the MTT assay.

MAIN TEST
- MTT assay results: The mean corrected percent tissue viability of the RhCE replicates treated with the test substance was 85.49%, versus 37.65% in the positive control (Methyl acetate). Refer Tables 7.3.2/1 for more details.

Any other information on results incl. tables

Table 7.3.2/1: Main test - Individual and mean corrected OD values and tissue viabilities for the test item, the negative and positive controls

 

	Tissue	OD	Mean OD/disc (#)	Mean OD/product	Viability %	Mean viability %	Difference of viability %
Negative control	1	0.911	0.906	0.776	116.83	100.00	33.66
		0.892
		0.917
	2	0.617	0.645		83.17
		0.659
		0.660
Positive control	1	0.308	0.313	0.292	40.36	37.65	5.42
		0.313
		0.319
	2	0.269	0.271		34.95
		0.273
		0.271
Test item	1	0.687	0.685	0.663	88.33	85.49	5.67
		0.683
		0.685
	2	0.616	0.641		82.66
		0.674
		0.635

#: mean of 3 values (triplicate of the same extract)

OD: optical density

 

Note

- The difference of viability between the two replicates of the negative control group was 33.66% instead of ≤20%. Considering the results obtained, this deviation was considered as without impact on the conclusion of the study.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

In accordance with Regulation EC No 1272/2008 and GHS Regulation, the test substance was identified as not requiring classification for eye irritation or serious eye damage. No hazard statement and no signal word were required.

Executive summary:

An in vitro eye irritation test using the Reconstructed human Cornea-like Epithelium (RhCE) (EpiOcular™ tissue) model was performed according to Guideline OECD 492 and in compliance with GLP to predict the acute eye irritation potential of the test substance.

The test substance was applied, as supplied, at the dose of 50 µL to two DPBS pre-treated RhCE (EpiOcular™ tissue model) during 30 minutes at 37°C, 5% CO2, 95% humidity (standard culture conditions). The exposure period was followed by extensive rinsing with DPBS at room temperature, a 12-minute post-exposure immersion period at room temperature and a 2-hour post-exposure incubation at standard culture conditions. The tissue viability was measured by performing a MTT assay.

In the preliminary tests, the test substance was found not to have direct MTT reducing properties or colouring potential. In the main test, the mean corrected percent tissue viability of the RhCE replicates treated with the test substance was 85.49%, versus 37.65% in the positive control (Methyl acetate).

Therefore, in accordance with Regulation EC No 1272/2008 and CLP Regulation, the test substance was identified as not requiring classification for eye irritation or serious eye damage. No hazard statement and no signal word were required.