Extract of Boswellia serrata (Burseraceae) obtained from exudate by solvent extraction

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 May - 01 June 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP study performed according to OECD Guideline 439 without any deviation.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

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)

Version / remarks:

adopted 28 July 2015

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

dated 23 July 2009

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Remarks:

27 April 2017

Test material

Test material information

Constituent 1

Reference substance name:

Extract of Boswellia serrata (Burseraceae) obtained from exudate by solvent extraction

EC Number:

947-377-6

IUPAC Name:

Extract of Boswellia serrata (Burseraceae) obtained from exudate by solvent extraction

Test material form:

solid: particulate/powder

Remarks:

off-white powder (as reported in the description of the substance)

Details on test material:

Name Boswellia serrata extract (as reported in the report)
Other Name BOSWELLIA SERRATA POUDRE
Batch no. LS210317
Appearance off-white powder
Composition 100% Boswellia serrata extract
CAS No. 97952-72-2
EINECS-No. 308-366-6
Production date Mar. 2017
Expiry date Mar. 2019
Storage Room Temperature (20 ± 5°C), keep away from light/ humidity/ -under inert gas

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: Used as supplied

In vitro test system

Test system:

human skin model

Source species:

other: RECONSTRUCTED HUMAN EPIDERMIS

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 (Episkin SA, RHE/S/17 Batch No. 17-RHE-063) were received on 30 May 2017.
- 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 25 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 during 42 minutes at room temperature, at the dose of 16 mg, to 5 living skin models, previously moistened with 10 µL of distilled water.
- 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 nylon mesh was removed and the human epidermises were washed with 25 x 1 mL of DPBS. The rinsed tissues were checked for any coloration and noted to be whitish, comparable coloration to that of the negative control tissues. They were incubated for a 42-hour post-treatment incubation-period in fresh medium at 37°C, 5% CO2. Then, the epidermis were put in contact with the MTT solution, except the two tissues for the non-specific colour control which were placed in the maintenance medium for 3 hours at 37°C, 5% CO2.

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
- As the test item was identified as potentially causing colour interferences: True viability % = [(OD of living tissues exposed to test item - OD of living tissues exposed to test item incubated with medium without MTT) / OD of living tissues exposed to negative control] x 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):

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

Number of replicates:

5 living human skin models including 2 for colour controls

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Remarks:

mean

Run / experiment:

main test (duration of exposure: 42 minutes)

Value:

95.9

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 white suspension with test item on top of the MTT solution was observed after 3 hours of incubation between 36.9°C and 37.6°C, 5% CO2. Therefore, there was no direct interaction between the test item and MTT.
- Test for the detection of the colouring potential of the test item:
In water, a white suspension with test item on top of the MTT solution was obtained after 1 hour of incubation between 36.9°C and 37.6°C, 5% CO2.
In isopropanol, a homogeneous yellow suspension was obtained after 2 hours of incubation at room temperature. Since a change of coloration was observed in isopropanol, a spectral analysis was done in the isopropanol supernatant.
- Spectral analysis of the test item in isopropanol:
The mean of the corrected OD (blank subtracted) was 0.09 in isopropanol which is higher than 0.08 (value corresponding to approximately twice the OD of the extracting solvent). Therefore, the test item was identified as causing colour interference with the viability assay and two viable control tissues were added to the study which underwent the entire testing procedure but were incubated with medium instead of MTT solution during the MTT incubation step to generate a non-specific colour (NSC living) control.


MTT VIABILITY ASSAY RESULTS
- The mean percent viability of the treated tissues was 95.9%, versus 1.3% in the positive control (5% Sodium Dodecyl Sulfate).
- The mean percent tissue viabilities obtained with the negative controls and positive controls were within the range of historical data and therefore validated the experiment.

Any other information on results incl. tables

Table 7.3.1/1: Main test - Individual and mean OD values and tissue viabilities for the test item, the negative and positive controls

 

	Skin tissues	OD	Mean OD/disc (#)	Mean OD/product	Viability %	Mean viability %	Standard deviation (SD)
Negative control	1	0.965	0.966	0.903	106.9	100.0	6.2
		0.980
		0.954
	2	0.887	0.887		98.2
		0.873
		0.901
	3	0.860	0.857		94.9
		0.852
		0.859
Positive control	1	0.013	0.012	0.011	1.3	1.3	0.1
		0.011
		0.013
	2	0.011	0.010		1.1
		0.009
		0.010
	3	0.013	0.012		1.3
		0.012
		0.013
Test item	1	0.931	0.929	0.865	102.8	95.8	8.6
		0.953
		0.904
	2	0.796	0.778		86.1
		0.804
		0.735
	3	0.970	0.888		98.3
		0.928
		0.767
Test item (NSC control)	1	-0.002	-0.002	-0.001	-0.2	-0.1	0.2
		-0.003
		-0.002
	2	-0.001	0.000		0.0
		-0.001
		-0.003
Test item (corrected)						95.9

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

OD: optical density

 

Acceptability criteria:

- SD ≤ 18%;

- Negative control: OD value of the 3 replicates in the range ≥0.8 and ≤3.0

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.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

Under the test conditions and in accordance with Regulation EC No. 1272/2008, the test item was considered as non-irritant to skin. It corresponds to UN GHS No Category. No hazard statement or signal word is 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 substance.

The test item was applied during 42 minutes, at the dose of 16 mg, to 3 living Reconstructed Human epidermis (SkinEthic RHE® model) previously moistened with 10 µL of distilled water. The treatment of the epidermis was followed by a rinse with 25 mL of DPBS and a 42 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 living Human skin model surfaces were treated in the same manner but they were incubated in culture medium instead of MTT solution in order to generate nonspecific living colour controls.

The mean corrected percent viability of the treated tissues was 95.9%, versus 1.3% in the positive control (5% Sodium Dodecyl Sulfate). The mean percent tissue viabilities obtained with the positive control and negative controls were within the range of historical data and therefore validated the experiment.

Under the test conditions and in accordance with Regulation EC No. 1272/2008, the test item was considered as non-irritant to skin. It corresponds to UN GHS No Category. No hazard statement or signal word is required.