1-(5-propyl-1,3-benzodioxol-2-yl)-1-ethanone

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22-27 January 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP study conducted according to OECD test Guideline No. 439 with minor deviation.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2014

Report date:

2014

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)

Deviations:

yes

Remarks:

historical data are not reported

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

historical data are not reported

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Remarks:

UK GLP Compliance Programme (inspected on 10 July 2012 / signed on 30 November 2012)

Test material

Test material information

Constituent 1

Reference substance name:

1-(5-propyl-2H-1,3-benzodioxol-2-yl)ethan-1-one

EC Number:

700-902-0

Cas Number:

1370699-98-1

Molecular formula:

C12H14O3

IUPAC Name:

1-(5-propyl-2H-1,3-benzodioxol-2-yl)ethan-1-one

Test material form:

liquid

Details on test material:

- Physical state: Colourless liquid
- Water solubility: 2.16 g/L
- Vapour pressure: 0.33 Pa (at 20°C) and 0.59 Pa (at 25°C)
- Partition coefficient: 2.69 (HPLC, 2013)
- Storage Conditions: 6 ± 2 °C, protected from light, under nitrogen in the original container
- Stability under test conditions: Not specified, assumed to be stable

Specific details on test material used for the study:

- Purity test date: 30 October 2013
- Storage Conditions: ca. 4 °C in the dark under nitrogen

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EPISKIN™ Reconstructed Human Epidermis Model Kit, SkinEthic Laboratories, Lyon, France
- Tissue batch number(s): 14-EKIN-001
- Production date: not reported
- Shipping date: 21 January 2014
- Delivery date: 21 January 2014
- Expiry date: 27 January 2014
- Date of initiation of testing: 22 January 2014

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: room temperature
- Temperature of post-treatment incubation (if applicable): 37 °C

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: not reported
At the end of the exposure period, each tissue was removed from the well using forceps and rinsed using a wash bottle containing DPBS with Ca++ and Mg++. Rinsing was achieved by filling and emptying each tissue insert for approximately 40 seconds using a constant soft stream of DPBS to gently remove any residual test item.
- Observable damage in the tissue due to washing: none reported
- Modifications to validated SOP: none reported

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 0.3 mg/mL in DPBS
- Incubation time: 3 hours
- Spectrophotometer: Anthos 2001 microplate reader
- Wavelength: 562 nm (without a reference filter)
- Filter: not applicable
- Filter bandwidth: not applicable
- Linear OD range of spectrophotometer: no data reported

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: negative control OD values: 1.030, 0.970 and 0.939 (historical control not reported).
- Barrier function: IC50= 2.1 mg/mL ( ≥ 1.5 mg/mL)
- Morphology: well differenciated epidermis consisting of a basal layer, several spinous and granular layers and a thick stratum corneum
- Contamination: : absence of bacteria, fungus and mycoplasma
- Reproducibility: not reported

CONTROL TISSUES USED IN CASE OF MTT DIRECT INTERFERENCE
- Fresh tissues / killed tissues: water-killed tissues
- Procedure used to prepare the killed tissues (if applicable): Water-killed tissues were prepared by placing untreated EPISKIN™ tissues in a 12-well plate containing 2.0 mL of sterile distilled water in each well. The tissues were incubated at 37°C, 5% CO2 in air for 48 ± 1 hours. At the end of the incubation the water was discarded. Once killed the tissues were stored in a freezer (−14 to −30°C) for up to 6 months. Before use each tissue was thawed by placing in 2.0 mL of maintenance medium for approximately 1 hour at room temperature. In addition to the normal test procedure, the MTT reducing test item was applied to three water-killed tissues. In addition, three water-killed tissues remained untreated. The untreated water-killed controls showed a small amount of MTT reduction due to residual reducing enzymes within the killed tissue.
- N. of replicates : 3
- Method of calculation used: Relative mean viability (%) = (Mean OD562 of test item / Mean OD562 of negative control) x 100

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 viability after the 15-min exposure period followed by the 42h post-exposure period is less or equal to 50%
- The test substance is considered to be non-irritant to skin if the viability after the 15-min exposure period followed by the 42h post-exposure period is greater than 50%

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 10 μL of the test item was applied to the epidermis surface.
- Concentration (if solution): Undiluted

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 10 μL of DPBS
- Concentration (if solution): undiluted

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 10 μL of SDS
- Concentration (if solution): 5% w/v

Duration of treatment / exposure:

Triplicate tissues were treated with the test item for an exposure period of 15 minutes at room temperature.
At the end of the exposure period, tissues were rinsed and incubated at 37 °C, 5% CO2 in air for 42 h.

Duration of post-treatment incubation (if applicable):

- On Day 3, at the end of the 42 h post-treatment incubation period: MTT test (MTT Loading/Formazan Extraction) was performed and tissues were incubated for 3 h at 37 °C, 5 % CO2 in air.
- On Day 6, at the end of the formazan extraction period: At the end of the formazan extraction period each tube was mixed thoroughly and duplicate 200 μL samples were transferred to the appropriate wells of a pre-labeled 96-well plate. The optical density was measured at 562 nm (without a reference filter) using the Anthos 2001 microplate reader.

Number of replicates:

Triplicate tissues for test item, negative and positive controls

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

15 minute exposure period and 42 h post-exposure incubation period

Value:

8.1

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

positive indication of irritation

Other effects / acceptance of results:

- Direct MTT Reduction: An assessment found the test item was able to directly reduce MTT. Therefore, an additional procedure using water-killed tissues was performed during the determination of skin irritation potential. However, the results showed a negligible degree of interference due to direct reduction of MTT occurred (OD562 of the treated killed tissues = 0.005 following subtraction of the untreated killed tissues; Treated killed tissues = 0.067 – untreated killed tissues = 0.062 = 0.005). It was therefore considered unnecessary to use the results of the water-killed tissues for quantitative correction of results or for reporting purposes.

- Test item: The relative mean viability of the test item treated tissues was 8.1% after a 15-Minute exposure period and 42 hours post-exposure incubation period. It was considered unnecessary to perform IL-1α analysis as the results of the MTT test were unequivocal.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: The mean OD562 for the negative control treated tissues was 0.980 and the standard deviation value of the percentage viability was 4.7%. The negative control acceptance criterion was therefore satisfied.
- Acceptance criteria met for positive control: The relative mean tissue viability for the positive control treated tissues was 5.5% relative to the negative control treated tissues and the standard deviation value of the percentage viability was 0.4%. The positive control acceptance criterion was therefore satisfied.
- Acceptance criteria met for variability between replicate measurements: The standard deviation calculated from individual percentage tissue viabilities of the three identically treated test item tissues was 1.6%. The test item acceptance criterion was therefore satisfied.

Any other information on results incl. tables

Table 7.3.1/1: Mean OD562 Values and Percentage Viabilities for the Negative Control Item, Positive Control Item and Test Item

 

Item	OD562 of tissues	Mean OD562 of triplicate tissues	± SD of OD562	Relative individual tissue viability (%)	Relative mean viability (%)	± SD of Relative mean viability (%)
Negative Control Item⊕	1.030	0.980	0.046	105.1	100*	4.7
	0.970			99.0
	0.939			95.8
Positive Control Item⊕	0.050	0.054	0.004	5.1	5.5	0.4
	0.058			5.9
	0.053			5.4
Test Item	0.064	0.080	0.016	6.5	8.1	1.6
	0.095			9.7
	0.080			8.2

 

SD = Standard deviation

∗= The mean viability of the negative control tissues is set at 100%

⊕= Control group shared with Harlan study number 41304108

OD562 = Optical Density

Applicant's summary and conclusion

Interpretation of results:

Category 2 (irritant) based on GHS criteria

Conclusions:

Under the experimental conditions of this study, the test item is classified as "Category 2 irritant" according to the Annex VI of the Regulation (EC) No. 1272/2008 (CLP) and to the GHS.

Executive summary:

An in vitro skin irritation study was performed according to the OECD Guideline 439 and in compliance with GLP, using the EPISKIN^TM reconstructed human epidermis model. 

Triplicate tissues were treated with the test item for an exposure period of 15 minutes. At the end of the exposure period each tissue was rinsed before incubating for 42 hours. At the end of the post-exposure incubation period each tissue was taken for MTT-loading. The maintenance medium from beneath each tissue was transferred to pre-labeled micro tubes and stored in a freezer for possible inflammatory mediator determination. After MTT-loading a total biopsy of each epidermis was made and placed into micro tubes containing acidified isopropanol for extraction of formazan crystals out of the MTT-loaded tissues. At the end of the formazan extraction period each tube was mixed thoroughly and duplicate 200 μL samples were transferred to the appropriate wells of a pre-labeled 96-well plate. The optical density was measured at 562 nm. Data are presented in the form of percentage viability (MTT reduction in the test item treated tissues relative to negative control tissues).

 

The relative mean viability of the test item treated tissues was 8.1% after the 15-Minute exposure period and 42 h post-exposure incubation period.

 

The mean OD562 for the negative control treated tissues was 0.980 and the standard deviation value of the percentage viability was 4.7%. The relative mean tissue viability for the positive control treated tissues was 5.5% relative to the negative control treated tissues and the standard deviation value of the percentage viability was 0.4%. The negative and positive controls acceptance criterion was therefore satisfied. The standard deviation calculated from individual percentage tissue viabilities of the three identically treated test item tissues was 1.6%. The test item acceptance criterion was therefore satisfied. 

 

Under the experimental conditions of this study, the test item is classified as "Category 2 irritant" according to Annex VI of the Regulation (EC) No. 1272/2008 (CLP) and to the GHS.