Octanoic acid, 2-phenoxyethyl ester

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 Oct - 01 Dec 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Version / remarks:

adopted Apr 2004

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, München, Germany

Test material

Test material information

Constituent 1

Reference substance name:

2-phenoxyethyl octanoate

EC Number:

607-240-0

Cas Number:

23511-73-1

Molecular formula:

C16H24O3

IUPAC Name:

2-phenoxyethyl octanoate

Radiolabelling:

yes

Administration / exposure

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: Skin membranes of female human abdominal origin sourced from cosmetic surgery were used. Due to inter-individual variability skin from 4 different donors was used.
- Skin samples are either purchased from Biopredic International, France or prepared at Eurofins Munich in house (skin obtained from Hepacult/HTCR).
- Type of skin: Human abdominal skin without stretch marks, hair, moles or birthmarks. The dermatomed skin discs (200 to 400/500 µm) comprising the stratum corneum, the epidermis and part of the dermis showed a diameter of 16 mm.
- Thickness of skin (in mm): undiluted test substance: 0.385 - 0.458; diluted test substance: 0.356 - 0.442
- Membrane integrity check: After visual check of the skin membrane, the skin in the assembled diffusion cells was checked for barrier integrity using tritiated water. Therefore, after equilibration of the skin membranes for approximately 15 min, 40 µL of tritiated water (1 kBq) were applied to the skin surface for 20 min. The receptor fluid flow was regulated to deliver about 0.2 mL/h. The unabsorbed material was then blotted with a cotton-tipped applicator and 40 µL PBS was applied to the skin surface. Effluent from the flow cell was collected for an additional 60 min. Skin was regarded as being undamaged if not more than 2% of the applied radioactivity was recovered from the receptor fluid.
- Storage conditions: ≤ -15 °C

PRINCIPLES OF ASSAY
- Diffusion cell: The diffusion cell is designed with a PTFE-donator and -acceptor part of the flow through diffusion cell for horizontal exposure of the skin surface.
- Receptor fluid: 50% ethanol
- Flow-through system: The diffusion cells were set in a microprocessor controlled thermostatisation block. A multi-channel peristaltic pump was connected with the receptor part of the diffusion cell and a programmable fraction collector was responsible for collecting the samples. The receptor fluid flow was regulated to deliver about 0.2 mL/h.
- Test temperature: undiluted test substance: 31.1 - 33.5 °C (8 h) and 31.4 - 33.1 °C (24 h); diluted test substance: 32.3 - 33.8 °C (8 h) and 31.9 - 33.6 °C (24 h)
- Other: 10 µL/cm² were applied onto the skin surface (0.78 mm²), depending on the physical state of the test formulation (solid/liquid). Two different concentrations of the test item were tested. For each concentration - undiluted and diluted concentration - of the formulation 10 replicates were set up. After an exposure period of 8 h the test item was washed off with a cleansing agent (1% aqueous soap solution, “Reine Pflanzenöl Kernseife”, Haslinger Seifen & Kosmetik GmbH, Charge: 2981). Residual test item was wiped from the donor side of the diffusion cell and the skin surface with a cotton bud. Additionally various rinsing steps with receptor fluid were performed to remove the remaining test item. The cotton buds and the rinsing liquid were stored at ≤ -15°C for further analysis of the remaining test item. After a 24 h period the experiment will be terminated. Sampling times of receptor fluid were 1, 2, 4, 8, 12, 16 and 24 h. The receptor fluid flow was regulated to deliver about 0.2 mL/h. The skin discs were removed from the chambers and stripping of the upper skin layers was performed. Skin was stripped with 15 pieces of adhesive tape, whereas groups of the sequential layers will be pooled. Tape stripping was terminated, if there was evidence that the stratum corneum had been completely removed. Up to 100 µL of each fraction of the receptor fluid were mixed with 2 mL scintillation cocktail (UltimaGoldTM, Perkin Elmer). The quantitatively collected residual test item (cotton buds) was supplemented with 10 mL scintillation cocktail and incubated in a water bath at 50 °C for about 60 minutes. The exposed skin discs and strips were incubated with 4 mL or 3 mL SolvableTM (Perkin Elmer), respectively over night at 50°C. After lysis of the skin and cooling down to room temperature, 100 µL of this extract were added to 2 mL of the scintillation cocktail.
The amount of test item in the receptor fluid, the quantitatively collected residual, non penetrated test item (skin wash), the skin and the strips were analyzed using a β-counter (Tricarb, Perkin Elmer).

Results and discussion

Absorption in different matrices:

- Receptor fluid (in vitro test system): In the receptor fluid mean values of 0.28% (SD: 0.31%) of the undiluted test item and 3.67% (SD: 3.52%) of the 10% test item formulation were detected.
- Skin preparation (in vitro test system): In the skin mean values of 3.06% (SD: 0.84%) of the undiluted test item and 9.78% (SD: 4.79%) of the 10% test item formulation were detected.

Total recovery:

- Total recovery: Mean recovery rates were 100.26% and 95.11% for the undiluted and the 10% formulation of the test item, respectively.

Percutaneous absorption

Percutaneous absorption 1

Key result

Time point:

24 h

Dose:

10 µL/cm²

Parameter:

amount

Remarks:

mean

Absorption:

6.78 %

Remarks on result:

other: undiluted test item

Percutaneous absorption 2

Key result

Time point:

24 h

Dose:

10 µL/cm²

Parameter:

amount

Remarks:

mean

Absorption:

18.85 %

Remarks on result:

other: 10% test item solution in (in Basic Formulation W/O Lotion mit Tegosoft XC+DEC)

Any other information on results incl. tables

Table 1: Results (undiluted)

	1	2	3	4^d	5	6^d	7	8	9^d	10	Mean^e	SD
Skin Wash 8h	77.38	81.63	85.27	77.52	79.87	78.10	77.40	87.77	64.87	82.00	81.62	3.88
Skin Wash 24 h	3.04	3.86	2.55	1.06	1.98	1.19	4.52	2.16	11.66	2.06	2.88	0.98
Chamber wash lid	0.23	0.70	0.54	0.43	0.13	0.29	0.66	0.30	0.71	0.36	0.42	0.22
Strips 1-2	8.18	4.68	5.89	7.41	4.98	4.05	8.68	3.69	14.94	7.27	6.20	1.89
Strips 3 - ∞	7.66	5.90	2.64	6.91	7.08	4.20	5.34	3.53	4.15	4.71	5.27	1.81
Skin	3.17	2.76	2.26	5.65	4.67	11.12	3.09	2.15	1.83	3.31	3.06	0.84
Receptor Fluid (RF)	0.08	0.22	0.43	0.67	0.90	0.29	0.15	0.07	1.71	0.08	0.28	0.31
Gauze	0.23	0.22	0.37	0.27	0.28	0.69	0.12	0.23	0.08	0.19	0.24	0.08
Chamber wash RF	0.04	0.03	0.05	0.07	0.09	0.07	0.03	0.10	0.06	0.03	0.05	0.03
Total	100.00	100.00	100.00	100.00	100.00	100.00	100.00	100.00	100.00	100.00	100.00	0.00
Absorption [%]^a	11.18^b	3.24	5.75^b	6.66	13.03^b	16.37	3.39	2.55	7.82	8.31^b	6.78^c	4.16
Recovery [%] normalized on applied dose	100.49	96.49	99.52	98.63	102.14	99.48	100.39	103.56	94.92	99.21	100.26	2.25
% of total absorption at 12h	70.64	85.15	59.55	96.49	8.98	5.56	92.31	77.83	45.64	69.30	66.25	27.46

In the total absorption (a) the amount of test item of skin, receptor fluid, gauze and chamber wash RF is included. In case of chamber 1, 3, 5 and 10 the strips 3 - ∞ were included in the calculation of the total absorption (b). The mean value for total absorption (c) is calculated of the total absorption values of the single replicates. Replicates 4, 6 and 9 were excluded for evaluation of results (d). Mean is calculated from skin replicates1, 2, 3, 5, 7, 8 and 10(e).

Replicates 4 and 6 were excluded for evaluation of results due to a lack of receptor fluid. Replicates 9 was excludedbecause the recovery rates was outside the range of 100% ± 10%.

Table 2: Results (10% formulation)

	1^d	2^d	3	4^d	5^d	6	7	8	9	10	Mean^e	SD
Skin Wash 8h	64.59	77.43	75.66	56.44	46.66	64.74	61.14	58.50	63.09	70.28	65.57	6.33
Skin Wash 24 h	4.85	1.49	3.20	4.46	5.52	4.33	5.98	4.15	4.06	5.55	4.54	1.03
Chamber wash lid	0.48	0.24	0.27	0.72	0.18	0.27	0.28	0.21	0.25	0.20	0.25	0.04
Cotton	0.61	0.64	0.65	0.62	0.69	0.64	0.67	0.62	0.59	0.66	0.64	0.03
Strips 1-2	3.32	2.16	3.99	5.14	7.63	7.41	8.93	10.23	7.18	4.06	6.97	2.53
Strips 3 - ∞	10.08	4.30	4.57	9.73	14.92	8.15	6.82	9.32	9.76	5.31	7.32	2.12
Skin	5.87	12.58	3.27	12.43	9.58	12.98	14.41	12.87	10.83	4.30	9.78	4.79
Receptor Fluid (RF)	6.45	0.24	7.11	7.67	13.93	0.22	0.21	2.64	3.17	8.66	3.67	3.52
Gauze	3.63	0.88	1.24	2.38	0.80	1.16	1.26	1.37	1.01	0.85	1.15	0.19
Chamber wash RF	0.13	0.04	0.04	0.42	0.09	0.11	0.29	0.09	0.06	0.12	0.12	0.09
Total	100.00	100.00	100.00	100.00	100.00	100.00	100.00	100.00	100.00	100.00	100.00	0.00
Absorption [%]^a	26.15	18.04	16.24	32.63	39.32	22.61	23.00	16.97	15.07	19.24	18.85	3.35
Recovery [%] normalized on applied dose	87.99	96.59	97.30	87.19	89.62	94.81	94.95	94.79	94.33	94.51	95.11	1.09
% of total absorption at 12h	49.33	37.37	48.68	1.06	44.21	61.83	61.72	97.14	93.39	45.03	67.96	22.23

In the total absorption (a) the amount of test item of skin, receptor fluid, gauze and chamber wash RF is included. In case of chamber 3, 6, 7 and 10 the strips 3 - ∞ were additionally included (b). The mean value for total absorption (c) is calculated of the total absorption values of the single replicates. Replicates 1, 2, 4 and 5 were excluded for evaluation of results (d). Mean is calculated from skin replicates 3, 6, 7, 8, 9 and 10(e).

Replicates 2 and 5 were excluded for evaluation of results due to a lack of receptor fluid. Replicates 1 and 4 were excludedbecause the recovery rates was outside the range of 100% ± 10%.