Essential oil of Citrus sinensis (Rutaceae) peel, terpene-free

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

From 16 July 2020 to 23 July 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2021

Report date:

2021

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted 18 June 2019

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:

Essential oil of Citrus sinensis (Rutaceae) peel, terpene-free

EC Number:

951-680-9

IUPAC Name:

Essential oil of Citrus sinensis (Rutaceae) peel, terpene-free

Test material form:

liquid

Details on test material:

Batch No. 0000448007
CAS No. not applicable
EC No. 951-680-9
Form: liquid
Colour: orange-yellow to green-yellow
Date received: 25 May 2020
Production date: 13 January 2020
Expiry date: 12 January 2021
Purity: 100% UVCB
Storage: fridge (6°C+/-3°C), darkness

In vitro test system

Test system:

human skin model

Source species:

other: reconstructed epidermises

Cell type:

non-transformed keratinocytes

Cell source:

other: foreskin

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE

- 0.50 cm² reconstructed epidermis were received, and on the same day, the insert (filter + epidermis) was gently removed from the agarose while avoiding leaving agarose on the polycarbonate filter. The inserts were placed in 6 wells culture plate which had been previously filled with 1 mL of growth medium (Episkin SA) during 2 hours and 05 minutes. Then just before treatment, the inserts were placed in 24 wells culture plate which had been previously filled with 300 µL of maintenance medium (Episkin SA).

TREATMENT

- The test item was applied as supplied, at the approximate dose of 16 mg, on the epidermal surface of 3 living human skin models during 42 minutes at room temperature.

- In the same experimental conditions, a positive control (5% SDS) and a negative control (DPBS) were carried out. The 5% SDS solution was prepared by weighing 0.5 g of SDS in a 10 mL volumetric flask qsp 10 mL of distilled water. Then, the preparation was magnetically stirred, just before the treatment. To ensure a good contact with the epidermises, during all the treatment period, the test item was recovered with a nylon mesh provided by Episkin SA.

REMOVAL OF TEST MATERIAL AND CONTROLS

- 42 minutes after the test item application, the human epidermises were washed with 25 x 1 mL of DPBS. The rinsed tissues were checked for any coloration and noted to be slightly brown instead of being whitish as for the coloration of the negative control tissues. Residual test item with brown coloration was noted on all Reconstructed Human epidermis after the rinse. They were incubated for a 41 hours post-treatment incubation period in fresh medium at 37°C, 5% CO2. Then, the epidermises were put in contact with the MTT solution.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE

- The cell viability was quantified by the measurement of the cell succinate dehydrogenase activity. This enzyme was responsible for the MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Thiazolyl blue; CAS No. 298-93-1)] reduction into blue formazan crystal that is quantitatively measured by Optical Density (OD) after extraction from tissues. The measured OD were proportional to the number of living cells.

- The skin samples were placed in 300 µL of a MTT solution at 1.0 mg/mL for 3 hours at 37°C, 5% CO2. The precipitated blue formazan product was then extracted using isopropanol during 2 hours under gentle agitation in the dark, and the concentration of formazan was measured by determining the OD (Optical Density) at 570 nm, just after dilution of the extracts (1:2 in isopropanol).

- The OD of MTT extract was measured in triplicate. The measurement of OD 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.

VIABILITY CALCULATION:

- The results were expressed as a viability percentage compared with the negative control: viability % = (mean OD test item / mean OD negative control) * 100

- Data from individual replicate tissues (OD values and calculated percent tissue viability data for the test item and controls), mean percent tissue viability and standard deviation for each individual test item and control were reported in Table 7.3.1/1.

PREDICTION MODEL / DECISION CRITERIA

The OD values obtained for each test sample were used to calculate a percentage of viability relative to the negative control, which was arbitrarily set at 100%. The cut-off values for the prediction of irritation associated with the RHE models were as follows:

- The test item is considered to be non-irritant to skin if the tissue viability after 42 minutes of exposure and 42 hours of post-treatment incubation is >50%.

- The test item is considered to be irritant to skin if the tissue viability after 42 minutes of exposure and 42 hours of post-treatment incubation is ≤ 50% and the result of a skin corrosion test is "non-corrosive". In accordance with Regulation EC No. 1272/2008, the test item has to be classified in Category 2 “Irritant”. The corresponding hazard statement is “H315: Causes skin irritation” with the signal word “Warning”.

- The test item is considered to be irritant or corrosive to skin if the mean percent tissue viability after 42 minutes exposure and 42 hours of post-treatment incubation is ≤50% and in absence of information on a skin corrosion test. In accordance with the Regulation (CE) No.1272/2008 and in absence of information on a skin corrosion test, the item has to be classified in Category 2 "Irritant" or in Category 1 "Corrosive". The corresponding hazard statement is respectively, "H315: Causes skin irritation" with the signal word "Warning" or "H314: Causes severe skin burns and eye damage" with the signal word "Danger".

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 16 mg
- Concentration (if solution): Undiluted

Duration of treatment / exposure:

42 minutes at room temperature

Duration of post-treatment incubation (if applicable):

41 hours post-incubation period at 37°C, 5% CO2

Number of replicates:

3 living human skin models

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Remarks:

mean

Value:

0

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

MTT VIABILITY ASSAY RESULTS
- The mean corrected percent viability of the treated tissues is 0.0%, versus 2.2% in the positive control (5% Sodium Dodecyl Sulfate).

- OTHER EFFECTS:
- Visible damage on test system: none
- Direct-MTT reduction: Yes, two additional killed control tissues were used to generate non-specific MTT reduction
- Colour interference with MTT: none.

DEMONSTRATION OF TECHNICAL PROFICIENCY: Proficiency chemicals were tested according to the OECD TG 439.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: yes, the negative control OD of the 3 replicates is >= 0.8 and <= 3.0 for every exposure time. The OD was measured after a 1:2 dilution of the formazan extracts in isopropanol; the acceptability criteria should be in the range >= 0.4 and <= 1.5 for the negative control.
- Acceptance criteria met for standard deviation: yes, the standard deviation should be <= 18%.

Applicant's summary and conclusion

Interpretation of results:

other: to be classified in Category 2 “Irritating to skin” or in Category 1 “Corrosive”

Conclusions:

The mean corrected percent viability of the treated tissues is 0.0%, versus 2.2% in the positive control (5% Sodium Dodecyl Sulfate). In accordance with the Regulation EC No. 1272/2008, the test item has to be classified in Category 2 “Irritating to skin” or in Category 1 “Corrosive”. The hazard statement “H315: Causes skin irritation” with the signal word “Warning” or “H314: Causes severe skin burns and eye damage” with the signal word “Danger” are required.

Executive summary:

An in vitro skin irritation test using the Reconstructed Human Epidermis (SkinEthic RHE® model) was performed according to the OECD Guideline 439 and in compliance with GLP to predict the acute skin irritation potential of the test item.

Test item was applied as supplied, at the dose of 16 mg, to 3 living Reconstructed Human epidermis (SkinEthic RHE^®model) during 42 minutes. The application was followed by a rinse with 25 mL of DPBS and a 41 hours post-incubation period at 37°C, 5% CO₂. Cell viability was then measured by enzymatic conversion of the vital dye MTT into a blue formazan salt that was quantitatively measured after extraction from tissues.Additionally, 2 killed Human skin model surfaces were treated (SkinEthic RHE® model) under the same conditions in order to generate non-specific MTT reduction.

 

The mean corrected percent viability of the treated tissues was 0.0%, versus 2.2% in the positive control (5% Sodium Dodecyl Sulfate). In accordance with the Regulation EC No. 1272/2008, the test item ORANGE ESS TYPE BRESIL DETERP 100% O15231 has to be classified in Category 2 “Irritating to skin” or in Category 1 “Corrosive”. The hazard statement “H315: Causes skin irritation” with the signal word “Warning” or “H314: Causes severe skin burns and eye damage” with the signal word “Danger” are required.