2-tert-pentylcyclohexyl acetate

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

The study was conducted between 10 May 2016 and 26 May 2016.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study is considered to be a reliability 1 as it has been conducted according to OECD Test Guideline 429 using a Local Lymph Node Assay method and in compliance with GLP.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

1

Reference substance name:

2-tert-pentylcyclohexyl acetate

EC Number:

267-500-0

EC Name:

2-tert-pentylcyclohexyl acetate

Cas Number:

67874-72-0

Molecular formula:

C13H24O2

IUPAC Name:

2-tert-pentylcyclohexyl acetate

Specific details on test material used for the study:

Coniferan
CAS #67874-72-0

In vivo test system

Test animals

Species:

mouse

Strain:

CBA/Ca

Sex:

female

Details on test animals and environmental conditions:

Animal Information
Female CBA/Ca (CBA/CaOlaHsd) strain mice were supplied by Envigo RMS B.V., Inc., Horst, The Netherlands. On receipt the animals were randomly allocated to cages. The animals were nulliparous and non pregnant. After an acclimatization period of at least 5 days the animals were selected at random and given a number unique within the study by indelible ink marking on the tail and a number written on a cage card. At the start of the study the animals were in the weight range of 15 to 23 g, and were 8 to 12 weeks old.

Animal Care and Husbandry
The animals were housed in suspended solid floor polypropylene cages furnished with softwood woodflakes. Free access to mains tap water and food (2014C Teklad Global Rodent diet supplied by Envigo RMS (UK) Limited, Oxon, UK) was allowed throughout the study.
The temperature and relative humidity were set to achieve limits of 19 to 25 C and 30 to 70%, respectively. The rate of air exchange was at least fifteen changes per hour and the lighting was controlled by a time switch to give 12 hours continuous light and 12 hours darkness.
The animals were provided with environmental enrichment items which were considered not to contain any contaminant of a level that might have affected the purpose or integrity of the study.

Study design: in vivo (LLNA)

Vehicle:

acetone/olive oil (4:1 v/v)

Concentration:

50% or 25% v/v in acetone/olive oil 4:1

No. of animals per dose:

Five

Details on study design:

Test Item
For the purpose of the study, the test item was used undiluted and freshly prepared as a solution in acetone/olive oil 4:1. This vehicle was chosen as it produced the most suitable formulation at the required concentration.
The test item was formulated within 2 hours of being applied to the test system. It is assumed that the formulation was stable for this duration.
No analysis was conducted to determine the homogeneity, concentration or stability of the test item formulation. This is an exception with regard to GLP and has been reflected in the GLP compliance statement.

Preliminary Screening Test
As no toxicological information was available regarding the systemic toxicity/irritancy potential of the test item, a preliminary screening test was performed using one mouse. The mouse was treated by daily application of 25 µL of the undiluted test item to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The mouse was observed twice daily on Days 1, 2 and 3 and once daily on Days 4, 5 and 6. Local skin irritation was scored daily according to the scale for Erythema (please see "any other information, inc. tables" for further details). Any clinical signs of toxicity, if present, were also recorded. The body weight was recorded on Day 1 (prior to dosing) and on Day 6.
The thickness of each ear was measured using a Mitutoyo 547 300S gauge (Mitutoyo Corporation), pre dose on Day 1, post dose on Day 3 and on Day 6. Any changes in the ear thickness were noted. Mean ear thickness changes were calculated between time periods Days 1 and 3 and Days 1 and 6. A mean ear thickness increase of equal to or greater than 25% was considered to indicate excessive irritation and limited biological relevance to the endpoint of sensitization.

Main Test
Test Item Administration
Groups of five mice were treated with the undiluted test item or the test item at concentrations of 50% or 25% v/v in acetone/olive oil 4:1. The preliminary screening test suggested that the test item would not produce systemic toxicity or excessive local skin irritation at the highest suitable concentration. The mice were treated by daily application of 25 µL of the appropriate concentration of the test item to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The test item formulation was administered using an automatic micropipette and spread over the dorsal surface of the ear using the tip of the pipette.
A further group of five mice received the vehicle alone in the same manner.

3H-Methyl Thymidine Administration
Five days following the first topical application of the test item or vehicle (Day 6) all mice were injected via the tail vein with 250 µL of phosphate buffered saline (PBS) containing 3H methyl thymidine (3HTdR: 80 µCi/mL, specific activity 2.0 Ci/mmoL, ARC UK Ltd) giving a total of 20 µCi to each mouse.

Observations
Clinical Observations: All animals were observed twice daily on Days 1, 2 and 3 and on a daily basis on Days 4, 5 and 6. Any signs of toxicity or signs of ill health during the test were recorded.
Body Weights: The body weight of each mouse was recorded on Day 1 (prior to dosing) and Day 6 (prior to termination).

Terminal Procedures
Termination: Five hours following the administration of 3HTdR all mice were killed by carbon dioxide asphyxiation followed by cervical separation. For each individual animal of each group the draining auricular lymph nodes were excised and processed. For each individual animal 1 mL of PBS was added to the lymph nodes.
Preparation of Single Cell Suspension: A single cell suspension of the lymph node cells for each individual animal was prepared by gentle mechanical disaggregation through a 200 mesh stainless steel gauze. The lymph node cells were rinsed through the gauze with 4 mL of PBS into a petri dish labeled with the study number and dose concentration. The lymph node cells suspension was transferred to a centrifuge tube. The petri dish was washed with an additional 5 mL of PBS to remove all remaining lymph node cells and these were added to the centrifuge tube. The lymph node cells were pelleted at 1400 rpm (approximately 190 g) for 10 minutes. The pellet was re suspended in 10 mL of PBS and re pelleted. To precipitate out the radioactive material, the pellet was re suspended in 3 mL of 5% Trichloroacetic acid (TCA).
Determination of 3HTdR Incorporation: After approximately 18 hours incubation at approximately 4 °C, the precipitates were recovered by centrifugation at 2100 rpm (approximately 450 g) for 10 minutes, resuspended in 1 mL of TCA and transferred to 10 mL of scintillation fluid. 3HTdR incorporation was measured by ß scintillation counting. The "Poly Q™" vials containing the samples and scintillation fluid were placed in the sample changer of the scintillator and left to stand in darkness for approximately 20 minutes. The purpose of this period of time in darkness was to reduce the risk of luminescence, which has been shown to affect the reliability of the results. After approximately 20 minutes, the vials were shaken vigorously. The number of radioactive disintegrations per minute was then measured using the Beckman LS6500 scintillation system (Beckman Instruments Inc, Fullerton, CA, USA).

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

Data was processed to give group mean values for disintegrations per minute and standard deviations where appropriate. Individual and group mean disintegrations per minute values were assessed for dose response relationships. Data was first assessed for suitability by analysis of normality and homogeneity of variance. If the assumptions that the data are both normally distributed and has homogeneity of variances, then parametric one way analysis of variance (ANOVA) and Dunnett’s multiple comparison procedure were used to determine statistical significance. If the assumptions were not met, non parametric Kruskal Wallis Rank Sum and Mann Whitney U test procedures were used.
Probability values (p) are presented as follows:
P<0.001 ***
P<0.01 **
P<0.05 *
P>0.05 (not significant)

Results and discussion

Positive control results:

α Hexylcinnamaldehyde, tech., 85% was considered to be a sensitizer under the conditions of the test.

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

SI

Remarks:

25 % v/v in acetone/olive oil 4:1

Value:

1.17

Results 2

Key result

Parameter:

SI

Remarks:

50 % v/v in acetone/olive oil 4:1

Value:

2

Results 3

Key result

Parameter:

SI

Remarks:

100 % v/v in acetone/olive oil 4:1

Value:

1.81

Cellular proliferation data / Observations:

Preliminary Screening Test
No signs of systemic toxicity or irritation indicated by an equal to or greater than 25% increase in mean ear thickness were noted.
Very slight erythema was noted on both ears on Day 3. No visual local skin irritation was noted on Days 1, 2 and 4 to 6.
Based on this information the undiluted test item and the test item at concentrations of 50% and 25% v/v in acetone/olive oil 4:1 were selected for the main test.

Main Test
Estimation of the Proliferative Response of Lymph Node Cells
The Stimulation Index expressed as the mean radioactive incorporation for each treatment group divided by the mean radioactive incorporation of the vehicle control group are as follows:

Concentration (%v/v) in
acetone/olive oil 4:1 Stimulation Index Result
25 1.17 Negative
50 2.00 Negative
100 1.81 Negative

Clinical Observations and Mortality Data
There were no deaths. No signs of systemic toxicity were noted in the test or control animals during the test.

Body Weight
Body weight change of the test animals between Day 1 and Day 6 was comparable to that observed in the corresponding control group animals over the same period.

Applicant's summary and conclusion

Interpretation of results:

other: Not a skin sensitiser

Remarks:

according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.and its updates

Conclusions:

The test item was considered to be a non-sensitizer under the conditions of the test.

Executive summary:

The skin sensitisation potential of the test substance, Coniferan was assessed according to OECD Test Guideline 429 using a Local Lymph Node Assay method. The test item was considered to be a non-sensitizer under the conditions of the test.