Lavender, Lavandula angustifolia, ext.

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Effects of ultraviolet radiation on the kinetics of in vitro percutaneous absorption of lavender oil.

Author:

Ben Salah M, Abderraba M, Tarhouni MR and Abdelmelek H.

Year:

2009

Bibliographic source:

Int J Pharm. 382(1-2):33-38.

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

An in vitro percutaneous absorption study was conducted to investigate the absorption of lavender essential oil on the rat skin.

GLP compliance:

not specified

Test material

Test material information

Test material form:

liquid

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Description: Pale-yellow liquid with a slightly camphoraceous odor

Radiolabelling:

no

Administration / exposure

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: Wistar rat
- Type of skin: Dorsal skin of Wistar rat
- Preparative technique: Dorsal skin of Wistar rat (180–200 g) was shaved by an electric clipper a night before of experiment and then the excised skin was immediately mounted on the receptor compartment with the SC-side facing upwards into the donor compartment and the dermal side facing downwards into the receptor compartment.
- The receptor compartment was filled with 10mL of normal saline and stirred constantly using a mini magnetic stirrer. The temperature of the jacketed diffusion cell was regulated by water thermostat maintained at 37 °C.
- The diffusion area of the skin was 3.14cm^2.

PRINCIPLES OF ASSAY
In vitro skin permeation experiments were carried out using cell diffusion:
- Following the 30mn equilibration, the lavender oil (500 mg) was applied onto the skin. The donor compartment was occluded with Parafilm. The essential oil was left on the skin surface for 4, 8, 12 and 24 h. After that, it was removed, and the skin was rinsed shortly with ethanol. The stratum corneum (SC) layers were separated using fragments of an adhesive tape. Collected samples of SC as well as the remaining skin epidermis/dermis (ED) were extracted by shaking in 5mL of ethanol for 24 h at room temperature in tightly closed vials. The ethanol extracts were collected into chromatographic vials and stored at 4 °C before the chromatographic analysis. The acceptor medium was extracted by diethylic ether and collected for analysis. The absorption experiment was repeated in triplicates. In order to study the effect of ultraviolet radiation on percutaneous absorption, the same protocol was adopted except that the system was exposed to an ultraviolet lamp with a wavelength of 366 nm which characterize the UVAI band.

QUALITATIVE AND QUANTITATIVE ANALYSIS
- Lavender oil was analysed by gas chromatography using a Hewlett-Packard (HP) 6890 with the flame ionisation detector and split–splitless injector. The chromatographic conditions were as follows: the detector temperature was 300 °C; the initial oven temperature was isotherm at 35 °C for 10 min, increasing gradually 3 °C/min up to 205 °C and isotherm at 205 °C for 10 min. HP-Innowax capillary column having a polar stationary phase (polyethylene glycol) was used. Chemical components were identified by gas chromatography of the essential oils with authentic substances, and by calculating their retention indices.
- The percentage composition of the essential oil was computed from gas chromatography peak areas using a HP CHEMSTATION data system. The main components of the lavender oil in the extracts of SC, ED and acceptor medium were identified and their concentration was calculated from their GC peak areas using a HP CHEMSTATION.

Results and discussion

Absorption in different matrices:

- Skin preparation (in vitro test system):
The percutaneous absorption of lavender oil was studied by the determination of its main components quantities that was accumulated during the times of exposition, and the system was protected against evaporation. During different times, no terpenes were detected in the acceptor fluid. The amounts determined in the separated skin layers after 4, 8, 12 and 24 h. The data of cumulated terpenes amounts in SC (stratum corneum) and ED (epidermis and dermis) are presented in Table 7.1.2/1. The concentrations were not normalized in respect of the collected SC mass.
- The terpenes penetrated easily into the skin but with different amounts. However, the amount of all terpenes increased during the first 4 h, then decreased from 4 until 12 h and finally increased again at 24 h.
- It was observed that an increase of the compounds until 4 h of absorption; then, between 4 and 8 h, the compounds decreased linearly to reach a minimum at 12 h. Finally, from 12 until 24 h the compounds increased again.
- Percutaneous absorption of lavender oil under ultraviolet radiation:
The percutaneous absorption of lavender oil with ultraviolet radiation (366 nm) was studied by the determination of its main component quantities accumulated during the times of exposition, and the system was protected against evaporation. During different times, no terpenes were detected in the acceptor fluid. The amounts determined in the separated skin layers after 4 and 8 h are presented in Table 7.1.2/2. The concentrations were not normalized in respect of the collected SC mass.
- The ultraviolet radiation altered the cycle (charge-discharge) for terpenes (low lipophilicity) and increased the charge time. However, for terpenes (high lipophilicity), the ultraviolet radiation decreased the charge amplitude.

Percutaneous absorption

Percutaneous absorption 1

Key result

Time point:

4 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 483 ± 141 and 309 ± 66 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Linalool

Percutaneous absorption 2

Key result

Time point:

8 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 327 ± 37 and 534 ± 198 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Linalool

Percutaneous absorption 3

Key result

Time point:

12 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 110 ± 35.50 and 507 ± 9 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Linalool

Percutaneous absorption 4

Key result

Time point:

24 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 884 ± 462 and 929 ± 94 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Linalool

Percutaneous absorption 5

Key result

Time point:

4 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 427 ± 127 and 140.50 ± 7 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Linalyl acetate

Percutaneous absorption 6

Key result

Time point:

8 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 235 ± 76 and 286 ± 112 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Linalyl acetate

Percutaneous absorption 7

Key result

Time point:

12 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 101 ± 35 and 236 ± 27 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Linalyl acetate

Percutaneous absorption 8

Key result

Time point:

24 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 670 ± 319 and 464 ± 19 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Linalyl acetate

Percutaneous absorption 9

Key result

Time point:

4 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 123 ± 44 and 27 ± 6 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Carvacrol

Percutaneous absorption 10

Key result

Time point:

8 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 101 ± 13 and 88.5 ± 44 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Carvacrol

Percutaneous absorption 11

Key result

Time point:

12 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 10 ± 5 and 42 ± 5 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Carvacrol

Percutaneous absorption 12

Key result

Time point:

24 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 65 ± 25 and 83 ± 17 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Carvacrol

Percutaneous absorption 13

Key result

Time point:

4 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 184 ± 55 and 163 ± 40 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Camphor

Percutaneous absorption 14

Key result

Time point:

8 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 125 ± 17 and 244 ± 96.50 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Camphor

Percutaneous absorption 15

Key result

Time point:

12 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 37 ± 11 and 251 ± 5 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Camphor

Percutaneous absorption 16

Key result

Time point:

24 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 976 ± 629 and 557 ± 107 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

Camphor

Percutaneous absorption 17

Key result

Time point:

4 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 155 ± 54 and 120 ± 35 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

1,8-Cineol

Percutaneous absorption 18

Key result

Time point:

8 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 133 ± 21 and 183 ± 88.50 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

1,8-Cineol

Percutaneous absorption 19

Key result

Time point:

12 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 114 ± 73 and 189 ± 24 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

1,8-Cineol

Percutaneous absorption 20

Key result

Time point:

24 h

Dose:

500 mg

Parameter:

amount

Remarks on result:

other: absorption: 340 ± 207 and 641 ± 197 µg/cm2 in stratum corneum and epidermis/dermis, respectively

Remarks:

1,8-Cineol

Any other information on results incl. tables

Table 7.1.2/1: Absorption of Terpenes (µg/cm²) into rat skin layer

Test item	Time of exposure skin layer^a
	4 h	8 h	12 h	24 h
Linalool
SC	483 ± 141	327 ± 37	110 ± 35.50**	884 ± 462
ED	309 ± 66	534 ± 198	507 ± 9	929 ± 94*
Linalyl acetate
SC	427 ± 127	235 ± 76	101 ± 35**	670 ± 319
ED	140.50 ± 7	286 ± 112	236 ± 27	464 ± 19**
Carvacrol
SC	123 ± 44	101 ± 13	10 ± 5	65 ± 25
ED	27 ± 6	88.5 ± 44	42 ± 5	83 ± 17*
Camphor
SC	184 ± 55	125 ± 17	37 ± 11**	976 ± 629
ED	163 ± 40	244 ± 96.50	251 ± 5	557 ± 107*
1,8-Cineol
SC	155 ± 54	133 ± 21	114 ± 73	340 ± 207
ED	120 ± 35	183 ± 88.50	189 ± 24	641 ± 197

Determinate from experiments repeated in triplicates independently (mean ± S.E.M., n = 3).

8 h vs 4 h, 12 h vs 4 h and 24 vs 4 h

^aSC: stratum corneum; ED: epidermis and dermis

* p < 0.05

** p < 0.01

Table 7.1.2/2: Influence of UVAI radiation on Terpenes absorptions of (µg/cm²) into rat skin layer

Test item	Time of exposure skin layer^a
	4 h	8 h
Linalool
SC	169 ± 37	218 ± 90*
ED	176.50 ± 12*	317 ± 41
Linalyl acetate
SC	147 ± 40	76 ± 4**
ED	58 ± 7	75 ± 12
Carvacrol
SC	20 ± 5	11 ± 2
ED	12 ± 2	14 ± 2
Camphor
SC	41 ± 13	129 ± 69
ED	102 ± 6	166 ± 10*
1,8-Cineol
SC	12 ± 1	127 ± 83
ED	93 ± 4	166 ± 11.50*

Mean ± S.E.M., n=3. 8 h vs 4 h.

^aSC: stratum corneum; ED: epidermis and dermis

* p < 0.05

** p < 0.01

Applicant's summary and conclusion

Conclusions:

The terpenes penetrated easily into the skin but with different amounts. The amount of all terpenes increased during the first 4 h, then decreased from 4 until 12 h and finally increased again at 24 h. The ultraviolet radiation altered the cycle (charge-discharge) for terpenes (low lipophilicity) and increased the charge time. However, for terpenes (high lipophilicity), the ultraviolet radiation decreased the charge amplitude.

Executive summary:

An in vitro percutaneous absorption study was conducted to investigate the absorption of lavender essential oil on the rat skin. The pure oil was extracted from Lavandula angustifolia by steam distillation.

 

The essential oil (500 mg) was applied onto the rat skin and In vitro skin permeation experiments were carried out using cell diffusion. The diffusion area of the skin was 3.14 cm². The essential oil was left on the skin surface for 4, 8, 12 and 24 h. The amount of the compounds was determined using gas chromatography. Similarly, the amount of these compounds was analyzed for the skin exposed to ultraviolet radiation (UVAI) after 4, 8, 12 and 24 h. The percutaneous absorption of lavender oil with or without ultraviolet radiation (366 nm) was studied by the determination of its main components quantities that was accumulated during the times of exposition, and the system was protected against evaporation.

 

The chemical composition of lavender oil showed that terpenes are major compounds. The chemical identification and the quantitative estimation of lavender oil showed that it contained five main components: linalool (25.18%), linalyl acetate (21.71%), 1,8-cineol (14.12%), camphor (11.15%) and carvacrol (2.34%).

 

During different times, no terpenes were detected in the acceptor fluid. The amounts determined in the separated skin layers after 4, 8, 12 and 24 h. The terpenes penetrated easily into the skin but with different amounts. However, the amount of all terpenes increased during the first 4 h, then decreased from 4 until 12 h and finally increased again at 24 h. It was observed that an increase of the compounds until 4 h of absorption; then, between 4 and 8 h, the compounds decreased linearly to reach a minimum at 12 h. Finally, from 12 until 24 h the compounds increased again.

 

The ultraviolet radiation altered the cycle (charge-discharge) for terpenes (low lipophilicity) and increased the charge time. However, for terpenes (high lipophilicity), the ultraviolet radiation decreased the charge amplitude.