Citronellol

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Publication with detailed documentation, used for assessment

Data source

Reference

Reference Type:

publication

Title:

In Vitro Human Skin Penetration of Geraniol and Citronellol

Author:

Gilpin S., Hui X., Maibach H.

Year:

2010

Bibliographic source:

Dermatitis, Vol 21, No 1 (January/February): pp 41-48

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Citronellol

EC Number:

203-375-0

EC Name:

Citronellol

Cas Number:

106-22-9

Molecular formula:

C10H20O

IUPAC Name:

3,7-dimethyloct-6-en-1-ol

Test material form:

other: aqueous solution

Details on test material:

- Name of test material (as cited in study report): citronellol (1-14C)
- Physical state: aqueous solution
- Analytical purity: 99%
- Specific activity (if radiolabelling): 52 mCi/mmol

Radiolabelling:

yes

Test animals

Species:

human

Strain:

other: not applicable

Sex:

not specified

Administration / exposure

Type of coverage:

occlusive

Vehicle:

other: DEP and ethanol (3:1)

Duration of exposure:

24 hours

Doses:

2% and 5% citronellol (weight per volume). 20 µl dose solution of approximately 0.5 µCi radioactivity applied.

No. of animals per group:

Skin was obtained from four donors

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: Department of Pathology at the University of California,San Francisco
- Type of skin: Human cadaver skin without obvious signs of skin disease
- Preparative technique: dermatomed with a Padgett ElectroDermatome
- Thickness of skin (in µm): approx. 400
- Membrane integrity check: checked visually, transepidermal water loss (TEWL): TEWL values of less than 15 g/m2h were considered acceptable
- Storage conditions: obtained within 24 hours of donor death, immediately placed in aluminum foil and amply sealed and stored at ~ 20°C until used.


PRINCIPLES OF ASSAY
- Diffusion cell: continuous-flow diffusion cell (item LG-1084, Laboratory Glass Apparatus, Inc., Berkeley, CA)
- Receptor fluid: 6% polyethylene glycol and sodium phosphate-buffered saline (pH=7.4)
- Test temperature: approx. 32°C skin surface temp.
- Occlusion: Yes (plastic chamber with a 2.2 cm2 cotton pad, sealed with Parafilm M Laboratory Wrapping Film and a layer of adhesive tape)

Results and discussion

Percutaneous absorption

Percutaneous absorption 1

Dose:

2%

Parameter:

percentage

Absorption:

3.8 %

Remarks on result:

other: 24 hours

Percutaneous absorption 2

Dose:

5%

Parameter:

percentage

Absorption:

4.7 %

Remarks on result:

other: 24 hours

Any other information on results incl. tables

After 24 hours, citronellal had relatively low skin absorption rates. Dose recoveries for all compartments measured are given in a graph only. However, key information for the assessment of bioavailability and total recovery are given as table:

Mass Balance and Percutaneous Absorption of Citronellol by Human Skin in Vitro

Compound	Removed dose after 24h [%]*	Penetrated dose absorbed after 24h [%]*
Citronellol 2%	86.3+/-5.2	3.8+/-2.1
Citronellol 5%	81.6+/-3.8	4.7+/-1.9

*Values are means +/- SD. Number of determinations = 12.

Based on the text given in the results section, the following has been reported by the authors:

Increasing concentration increased absorption; Recovery for fragrance materials was good; Most of the dose was recovered in the skin washes; Recovery was much less for all other compartments; the cover compartments for 2% and 5% citronellol had the next highest dose recoveries (15.5% ± 3.9% and 10.7% ± 0.9%, respectively), followed by the tape strips (6.1%± 4.3% and 4.3% ± 0.3%, respectively). Examination of the time variable in box plots for the receptor fluid collection points showed a linear increase in the amounts of citronellol that penetrated the skin even though the overall values of absorption were quite small.