p-mentha-1,4(8)-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:

22-30 May 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study conducted in compliance with OECD Guideline No 439 without any deviation.

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:

2012

Report date:

2012

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Principles of method if other than guideline:

not applicable

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

p-mentha-1,4(8)-diene

EC Number:

209-578-0

EC Name:

p-mentha-1,4(8)-diene

Cas Number:

586-62-9

Molecular formula:

C10H16

IUPAC Name:

4-isopropylidene-1-methylcyclohexene

Test material form:

other: liquid

Details on test material:

Name of the test item (as cited in the study report): TERPINOLENE MONOCONSTITUENT
IUPAC Name of the test item: 4-isopropylidene-1-methylcyclohexene
Synonyms: 1-methyl-4-(1-methylethylidene)-cyclohexene; p-mentha-1,4(8)-diene
Substance type: monoconstituent
Batch No.: 122718
Purity: 97.9%
Impurities (identity and concentrations): gamma terpinene (0.7%), D and L limonene (0.1%)
This composition is within the specifications of the substance identity profile agreed within the SIEF.
Colour: colourless – slightly amber
Storage Conditions: +2°C to +8°C, under nitrogen and protected from light
Expiry Date: 11 October 2012

Test animals

Species:

human

Details on test animals or test system and environmental conditions:

Three-dimensional human epidermis model, supplied by SkinEthic Laboratories, Nice, France constituted by:
- a collagen type I matrix, coated with type IV collagen
- a differentiated and stratified epidermis model from human keratinocytes, obtained after 13-day culture period.
All biological components of the epidermis and the kit culture medium have been tested for the absence of viruses, bacteria and mycoplasma

Test system

Type of coverage:

other: not applicable

Preparation of test site:

other: not applicable

Vehicle:

unchanged (no vehicle)

Controls:

other: negative control: PBS+; positive control: 5 % (w/v) SDS solution

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 10 µL
- Concentration: Test material: undiluted; negative control: PBS+; positive control: 5 % (w/v) SDS solution

Duration of treatment / exposure:

15 ± 0.5 min

Observation period:

Post-treatment incubation period: 42 ± 1 h

Number of animals:

Three epidermis units were used per test material, positive and negative controls.

Details on study design:

TEST SYSTEM:
- Cell system used: EPISKIN® kit: three-dimensional human epidermis model
- Source: SKINETHIC Laboratories (Lyon, France)
- All biological components of the epidermis and the kit culture medium have been tested for the absence of viruses, bacteria and mycoplasma. The quality was assessed by an MTT cytotoxicity test and by histological examination (by SKINETHIC).

METHODOLOGY:
- Non-specific MTT reduction: 10 µL of the test item was added to each well of a 12-wells plate containing 2 mL of MTT solution (0.3 mg/mL) and colour of the solution was checked after incubation for 3 h ± 5 min at 37 ± 1 °C, 5 ± 1 % CO2, 95 ± 5% humidity (CO2 incubator).
- Staining power: 10 µL of the test item was agitated with 90 µL of mineral oil for 15 ± 0.5 min at room temperature and colour of the solution was checked.
- MTT conversion assay: The epidermis units were transferred from the kit into maintenance medium filled wells and pre-incubated for 24 ± 3 h at 37 ± 2 °C. After pre-incubation, the test materials (10 µL) were applied topically to the epidermal model (three epidermis units per test material, positive and negative controls) for 15 ± 0.5 min at room temperature. After rinsing with phosphate buffered saline, the epidermises were then incubated at 37 ± 2 °C for 42 ± 1 h (CO2 incubator). Aliquots of culture media were kept frozen (-20°C) for cytokine (IL-1α) further measurements. The viability was assessed by incubating the tissues for 3 h ± 5 min with MTT solution in a 12 well plate (0.3 mg/mL; 2 mL per well). The formazan precipitated was then extracted using acidified isopropanol (0.5 mL) and quantified spectrophotometrically at 570 nm using 96 well plates (200 μL/well). For each treated tissue the viability was expressed as a % relative to negative control tissues (mean).
- IL-1α assay: Standard or samples (200 µL) were added to each well containing 50 µL of diluent and incubated for 2 h ± 15 min at room temperature. After washing with buffer, 200 µL of conjugate IL-1α was added to each well and incubated for 1 h ± 10 min at room temperature. The wells were washed again and added with 200 µL of substrate solution. After incubation for 20 ± 5 min at room temperature, optical density was recorded at 450 nm on a microplate reader. Protein levels of IL-1α in the supernatant were expressed as pg/mL.

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

other: other: relative viability %

Value:

84.2

Remarks on result:

other:

Remarks:

Basis: mean. Time point: exposure: 15 min. Max. score: 100.0. Reversibility: other: not applicable. (migrated information)

In vivo

Irritant / corrosive response data:

Negative control:
Mean optical density: 0.855

Positive control:
Viability %: 25.1 ± 3.9
IL-1 α mean concentration: 250.1 pg/mL

Test material:
Viability %: 84.2 ± 2.2
IL-1 α mean concentration: 185.1 pg/mL

See tables 7.3.1/1 and 7.3.1/2 for data

Other effects:

Non-specific MTT reduction: terpinolene monoconstituent did not interact with MTT.

Staining power: terpinolene monoconstituent had no staining power on living epidermis.

Any other information on results incl. tables

Table 7.3.1/1: MTT conversion assay

		OD1	OD2	Mean	Standard Deviation	Viability %	Mean Viability %	Standard deviation
Negative control	Epidermis 1	0.827	0.878	0.853	0.036	99.7	100.0	3.7
	Epidermis 2	0.891	0.885	0.888	0.004	103.8
	Epidermis 3	0.828	0.822	0.825	0.004	96.5
	Mean	/	/	0.855	/	/
Positive control	Epidermis 1	0.242	0.254	0.248	0.008	29.0	25.1	3.9
	Epidermis 2	0.233	0.195	0.214	0.027	25.0
	Epidermis 3	0.206	0.158	0.182	0.034	21.3
P3	Epidermis 1	0.689	0.708	0.699	0.013	81.7	84.2	2.2
	Epidermis 2	0.748	0.705	0.727	0.030	85.0
	Epidermis 3	0.695	0.775	0.735	0.057	85.9

O.D. Optical Density

Table 7.3.1/2: Interleukine 1 alpha (IL-1α) assay

	OD			Concentration IL-1α (pg/mL)			Mean concentration IL-1α (pg/mL)	Standard deviation	CV	IL-1α final concentration (pg/mL) (treated/untreated)
	Epidermis 1	Epidermis 2	Epidermis 3	Epidermis 1	Epidermis 2	Epidermis 3
Negative control	0.022	0.031	0.023	-7.2	-6.0	-7.1	-6.8	0.69	-10.3%	/
Positive control	1.803	1.799	1.801	243.6	243.1	243.3	243.3	0.28	0.10%	250.1
P3	1.377	1.291	1.351	183.6	171.5	180.0	178.4	6.21	3.5%	185.1

 

Applicant's summary and conclusion

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

In an in vitro skin irritation study performed on reconstructed human epidermis, cell viability was higher than 50 % and therefore terpinolene monoconstituent is not irritant to skin according to Directive 67/548/EEC and CLP Regulation (EC) No 1272/2008.

Executive summary:

In an in vitro skin irritation study performed according to OECD Guideline No 439 and in compliance with GLP, 10 µL of terpinolene monoconstituent were applied topically to reconstructed human epidermis model (3 epidermis units/dose) for 15 ± 0.5 min at room temperature. After rinsing with phosphate buffered saline (PBS), epidermises were incubated at 37 ± 2 °C for 42 ± 1 h (CO₂ incubator). Aliquots of culture media were kept frozen (-20°C) for cytokine (IL-1α) measurements. The viability was assessed by incubating the tissues for 3 h ± 0.5 min with MTT solution in a 12 well plates (0.3 mg/mL; 2 mL per well). The formazan precipitated was then extracted using acidified isopropanol (0.5 mL) and quantified spectrophotometrically at 570 nm using 96 well plates (200 μL/well). SDS 5% (w/v) and PBS-treated epidermis were used as positive and negative controls, respectively.

Mean relative cell viability for the test item was 84.2 ± 2.2 %. Mean cell viability for the positive control was 25.1 ± 3.9 % and optical density value for the negative control epidermis was 0.855. Thus the validity of the test was confirmed. Mean IL-1 α concentrations of test item and positive controls were recorded to be 185.1 and 250.1 pg/mL, respectively.

Cell viability was > 50 %, therefore terpinolene monoconstituent is not irritant to skin according to Directive 67/548/EEC and CLP Regulation (EC) No 1272-2008.