Isopentyl p-methoxycinnamate

Endpoint summary

Description of key information

The skin irritation properties of isopentyl p-methoxycinnamate were investigated in an in vivo study in rabbits.  In addition a double-blind, randomised assessment of the irritant potential of sunscreen chemical dilutions, including isopentyl p-methoxycinnamate, was conducted in human volunteers.
The eye irritation properties of this compound were assessed in two in vitro studies, (HET-CAM and BCOP) test, as well as in an in vivo study in rabbits
The potential respiratory irritation properties of isopentyl p-methoxycinnamate were not studied.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12 December 1994 to 15 December 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.4 (Acute Toxicity: Dermal Irritation / Corrosion)

Deviations:

no

Principles of method if other than guideline:

not applicable

GLP compliance:

yes (incl. QA statement)

Species:

rabbit

Strain:

other: SPF albino

Details on test animals or test system and environmental conditions:

Animals = Four female SPF albino rabbits weighting 2.1-2.4 kg of the stock Mol:Russian from Mollegaard Breeding and Research Centre A/S, Ejby, DK-4623 Lille Skensved were used.
Housing = The study took place in animal room No. 1 provided with filtered air with a temperature of 21±3°C, relative humidity of 55±15% and air changes 10 times/h. The room was illuminated to give a 24 h cycle of 12 h light and 12 h darkness. Ligh was on from 6 a.m. to 6 p.m. During a pre-period of at least 1 week and throughout the experiment, the rabbits were caged in single 62 x 52 cm PPO cages with perforated floor.
Diet = A pelleted complete rabbit diet "Altromin 2123" from Chr. Petersen, DK-4100 Ringsted, Denmark was available ad libitum. Analyses for major nutritive components and significant contaminants are performed regularly on the diet.
Drinking water = The animals had free access to bottles with domestic quality drinking water acidified with hydrochloric acid to pH 2.5 in order to prevent microbial growth. Analyses for possible contaminants are performed regularly.

Type of coverage:

semiocclusive

Preparation of test site:

other: clipped

Vehicle:

other: Ethanol 96 % and diethyl phtalate (DEP) in a ration 1 : 1 (w/w)

Controls:

yes, concurrent vehicle

Amount / concentration applied:

Test concentrations (w/w): 100, 20, 10, 5, and %

Duration of treatment / exposure:

After an exposure of 4 h, the tape and patches were removed and the treated skin was cleaned with soap and luke warm water. The skin reactions were read 1 hour later.

Observation period:

After an exposure of 4 hours the tape and patches were removed and the treated skin was cleaned with soap and luke warm water. The skin reactions were read 1 h later.
Reading was also performed at 24, 48, and 72 h after termination of exposure.

Number of animals:

Four female SPF albino rabbits were used.

Details on study design:

The day before the experiment was started, the rabbits were weighted and an area of 10 x 10 cm on the back was clipped as closely as possible with an electric clipper.
On the experimental day, the rabbits were physically restrained on a test table, and the clipped area was divided into 6 test sites: 2 anterior located test sites, 2 centrally located test sites and 2 posterior located test sites. To each of 6 gauze patches (2.5 x 2.5 cm), 0.5 mL of 1 of the test concentrations or the vehicle was applied and the patches were placed on the appropriate test site at the back of each rabbit. The gauze patches were secured with a semi-occlusive dressing by means of a 1-cm wide adhesive tape and fixed with Scanpor tape, 4.5 cm width, loosely wound round the trunk. The application schedule was made by a computerized randomization programme.
After an exposure of 4 h, the tape and patches were removed and the treated skin was cleaned with soap and luke warm water. The skin reactions were read 1 h later. Reading was also performed at 24, 48, and 72 h after termination of exposure.

Irritation parameter:

erythema score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0.33

Max. score:

1

Reversibility:

not specified

Remarks on result:

no indication of irritation

Irritation parameter:

erythema score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

0

Reversibility:

not specified

Irritation parameter:

erythema score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

0

Reversibility:

not specified

Irritation parameter:

erythema score

Basis:

animal #4

Time point:

24/48/72 h

Score:

0

Max. score:

0

Reversibility:

not specified

Irritation parameter:

edema score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

0

Reversibility:

not specified

Irritation parameter:

edema score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritation parameter:

edema score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritation parameter:

edema score

Basis:

animal #4

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritant / corrosive response data:

see section "Any other information on results incl. tables" below

Other effects:

no other effects were observed

Under the experimental conditions described in the report, the mean score for erythema and oedema in the 4 rabbits used were as follow:

Test concentration	100 %	20 %	10 %	5 %	1 %	Vehicle
Erythema	0.3	0.0	0.0	0.0	0.0	0.0
Oedema	0.0	0.0	0.0	0.0	0.0	0.0

Interpretation of results:

GHS criteria not met

Conclusions:

Isopentyl p-methoxycinnamate was found to be not irritating to the skin of rabbits.

Executive summary:

The primary skin irritant effect of Neo Heliopan E1000 was investigated according to the method recommended in the current OECD guideline no. 404, "Acute Dermal Irritation/ Corrosion", 1992, and in the current EC guideline B.4 "Acute toxicity (skin irritation)", dated 29.12.1992. The study was extended to investigate 5 different concentrations of the test article and a vehicle control on each animal.

Four albinos rabbits were exposed to different concentrations of the test article at 6 skin sites on the back. After 4 h of exposure, the test article was removed and the skin was examined 1, 24, 48, and 72 h after termination of exposure.

Slight skin erythma was observed at 1 to 48 h after termination of exposure of the neat test article. Apart from that, no abnormalities were observed.

Accordingly, isopentyl p-methoxycinnamate was rated as being not irritating to the skin of rabbits.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

April 1971

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

no guideline followed

Principles of method if other than guideline:

According to ref.: J.H. Kay et col., J.Soc.Cos.Chem. 13/281, 1962

GLP compliance:

no

Species:

rabbit

Strain:

other: albino

Details on test animals or tissues and environmental conditions:

No data

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent no treatment

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.1 mL
- Concentration (if solution): undiluted

Duration of treatment / exposure:

Group I - 168 h (not rinsed)
Group II - 2 sec (rinsed)
Group III - 4 sec (rinsed)

Observation period (in vivo):

168 h (at 1, 24, 48, 72, 96 and 168 h)

Number of animals or in vitro replicates:

Group I - 3
Group II - 3
Group III - 3

Details on study design:

REMOVAL OF TEST SUBSTANCE
- Washing (if done): Group I: not rinsed; Group II: rinsed after 2 sec; Group III: rinsed after 4 sec
- Time after start of exposure: 2 sec and 4 sec

SCORING SYSTEM: according to ref.: J.H. Kay et col., J.Soc.Cos.Chem. 13/281, 1962

Irritation parameter:

conjunctivae score

Basis:

mean

Time point:

other: 1 h

Score:

3.3

Reversibility:

fully reversible within: 24 h

Remarks on result:

other: overall score from all groups

Irritant / corrosive response data:

A slight irritation of the conjunctivae was observed during the few hours after application of pure 2-Ethylhexyl 4-methoxycinnamate. This
irritation is manifested by the presence of some more capillaries injected into the eye treated than on the eye not treated. No effect could
be detected 24 hours after application of the test substance. No effect of rinsing was observed.

Other effects:

No data

Observation time	Animal no.	Group I conjunctivae	Group II conjunctivae	Group III conjunctivae	Results
1 h	1	A2	A1	A2	3.3
1 h	2	A1	A2	A1
1 h	3	A2	A2	A2
24 h	1				0
24 h	2
24 h	3

Interpretation of results:

GHS criteria not met

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

No effects on eye irritation could be detected 24 h after application of 2-ethylhexyl 4-methoxycinnamate.

Executive summary:

The eye irritation potential of 2-ethylhexyl 4-methoxycinnamate, a close structural analogue of isopentyl p-methoxycinnamate, was evalauted in a Draize test in albino rabbits.

2-ethylhexyl 4-methoxycinnamate

was injected into the left eye of 3 albino rabbits without rinsing, the left eye of another 3 albino rabbits were rinsed after 2 and 4 seconds, resp. Cornea, iris, and conjunctivae were examined. A slight irritation of the conjunctivae was observed during the few hours after application of pure

2-ethylhexyl 4-methoxycinnamate

. This irritation is manifested by the presence of some more capillaries injected into the eye treated than on the eye not treated. No effect, however small, could be detected 24 h after application of the test substance.

In view of the close chemical relationship between isopentyl p-methoxycinnamate and Neo Heliopan AV, the negative findings obtained with

2-ethylhexyl 4-methoxycinnamate

provide further evidence for the non-eye-irritancy of isopentyl p-methoxycinnamate in rabbits.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin irritation:

The in vivo skin irritation test in rabbits was conducted according to OECD guideline no. 404 and EU guideline B 4. Five concentrations of the test article were studied on each animal. Accordingly, 4 albino rabbits were exposed to 5 different concentrations of the test article and a vehicle control at 6 skin sites on the back. After 4 h of exposure, the test items were removed and the skin was examined at 1, 24, 48, and 72 h thereafter.

Slight skin erythma was observed at 1 to 48 h after termination of exposure of the neat test article. No further abnormalities were observed. Accordingly, isopentyl p-methoxycinnamate was rated as being not irritating to the skin of rabbits.

 

Further information on the skin irritation potential of isopentyl p-methoxycinnamate is available from a recently conducted double- blind, randomized photoirritation patch test in humans (Kerr et al. 2009; see the attached pdf file). Out of the 80 subjects analysed in this study, 1 and 3 subjects showed "doubtful" or "weakly positive" photoirritant reactions after the application of isopentyl p-methoxycinnamate at concentrations of 5% and 10%, respectively. No photoirritant reactions were observed when isopentyl p-methoxycinnamate was applied at a concentration of 2%. These findings suggest that isopentyl p-methoxycinnamate at higher concentrations might have a certain, albeit low, incidence (≤ 5%) to cause photoirritant skin reactions.

 

Eye irritation:

In the HET-CAM test, 0.2 mL of a solution or suspension of isopentyl p-methoxycinnamate (1% and 10% in olive oil) was applied to the Chorioallantois membrane of hen's eggs and incubated for 10 days. At 0.5, 2, and 5 min after application of the test item, the capillary blood vessels and the egg white were inspected for vascular injections, haemorrhage, and coagulation and the severity of the effects was rated using a numerical, time-dependent scale. Isopentyl p-methoxycinnamate was found to be "practically non- irritant" in this assay.

 

In the BCOP test, fresh bovine corneas, which had been pre- incubated with complete minimum essential medium at 32±1°C for 1 h, were treated with 750 µL of undiluted isopentyl p-methoxycinnamate or two dilutions (1% and 10%) of the test item in olive oil for 10 min at 32±1°C. NaOH (10% solution in demineralised water) and physiological NaCl solution were used as positive and negative control, respectively. 3 replicates were used for each treatment group. After removal of the test item and 2 h post- incubation, opacity and permeability values were measured.

While the positive control induced very severe irritation on the cornea, the negative control showed no irritation. Similarly, isopentyl p-methoxycinnamate did not induce any irritation at any of the three tested concentrations.

 

In the in vivo test for eye irritation/corrosion, eight rabbits were treated with 0.1 mL of isopentyl p-methoxycinnamate at a concentration of 50% in olive oil. The test item was applied in the conjunctival sac of the animals. After an exposure period of 1 min, the test item was rinsed off with physiological saline in 4 animals, whereas the test item was left on the eyes of the remaining 4 animals (no data given on the duration of the overall exposure period and the observation period). No irritant or corrosive effects were observed in any of the animals. However, all the data was not available for full assessment of this endpoint for isopentyl p-methoxycinnamate and the study was assigned a Klimisch 4 (not assignable). Therefore, data was read-across from the in vivo rabbit eye irritation study conducted with the read-across substance, 2 -ethylhexyl 4 -methoxycinnamate (Klimisch 2). Data from this study was also negative in this respect.

In summary,the negative result of the in vitro eye irritation findings for isopentyl p-methoxycinnamate were corroborated by the results of the HET-CAM and the BCOP test conducted with 2 -ethylhexyl 4 -methoxycinnamate. Similarly, 2 -ethylhexyl 4 -methoxycinnamate was negative in an in vivo eye irritation test in rabbits, thereby further corroborating the non-irritancy of isopentyl p-methoxycinnamate to the eye.

 

Justification for selection of skin irritation / corrosion endpoint:
Guideline study performed in accordance with GLP

Justification for selection of eye irritation endpoint:
The selected study is a Guideline study performed in accordance with GLP and has a Klimisch score of 2 (reliable with restrictions). The read-across substance 2-ethylhexyl 4-methoxycinnamate is of strong structural similarity with isopentyl p-methoxycinnamate such that similarities are expected in the eye irritation profile. The in vivo rabbit eye test with isopentyl p-methoxycinnamate is Klimisch score 4 (not assignable) due to the non-availability of the data. The in vitro eye irritation studies produced negative results for both substances.

Justification for classification or non-classification

Based on the results of the skin and eye irritation studies given above, isopentyl p-methoxycinnamate is not classified as skin or eye irritant according to the current EU-CLP regulation.

A classification of isopentyl p-methoxycinnamate for respiratory irritation is not possible, as no respiratory irritation studies were conducted with this compound.