3-phenyl-L-alanine

Endpoint summary

Description of key information

The LLNA with the analogous substance phenylglycine and the QSAR showed no skin sensitising potential.
Therefore, it can be concluded that Phenylalanine does not have a skin sensitising potential.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories B.V. (The Netherlands)
- Age at study initiation: 8 - 12 weeks
- Weight at study initiation: 19.4 to 23.6 g
- Housing: single
- Diet: pelleted standard diet, ad libitum
- Water: tap water, ad libitum
- Acclimation period: at least 5 days prior to the start of dosing under test conditions

ENVIRONMENTAL CONDITIONS
- Temperature: 22 +/- 2°C
- Humidity: 45-65%
- Air changes: data not available
- Photoperiod: artificial light 6.00 a.m. - 6.00 p.m.

Vehicle:

propylene glycol

Concentration:

5, 10, and 25%

No. of animals per dose:

4 females per group

Details on study design:

RANGE FINDING TESTS:
- Compound solubility:
A solubility experiment was performed according to the recommendations given by OECD 429. The highest test item concentration, which can be technically used was a 25 % suspension in propylene glycol.
- Irritation:
To determine the highest non-irritant test concentration, a pre-test was performed in two animals. Two mice were treated with concentrations of 10 and 25% each on three consecutive days. In the pre-test clinical signs were recorded within 1 hour and 24 ± 4 hours after each application as well as on day 7. At the tested concentrations the animals did not show any signs of irritation or systemic toxicity.
- Lymph node proliferation response: not determined.

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: LLNA
- Criteria used to consider a positive response:
A test item is regarded as a sensitiser in the LLNA if the following criteria are fulfilled:
> First, that exposure to at least one concentration of the test item resulted in an incorporation of 3HTdR at least 3-fold or greater than that recorded in control mice, as indicated by the stimulation index.
> Second, that the data are compatible with a conventional dose response, although allowance must be made (especially at high topical concentrations) for either local toxicity or immunological suppression.

TREATMENT PREPARATION AND ADMINISTRATION:
Each test group of mice was treated by topical (epidermal) application to the dorsal surface of each ear (left and right) with different test item concentrations of 5, 10, and 25% (w/v) in propylene glycol. The application volume, 25 µl, was spread over the entire dorsal surface (diameter ca. 8 mm) of each ear once daily for three consecutive days. A further group of mice was treated with an equivalent volume of the relevant vehicle alone (control animals).
Five days after the first topical application, all mice were administered with 250 µl of 81.9 µCi/ml 3HTdR (corresponds to 20.5 µCi 3HTdR per mouse) by intravenous injection via a tail vein.
Approximately five hours after treatment with 3HTdR all mice were euthanised.
The draining lymph nodes were rapidly excised and pooled per group (8 nodes per group). Single cell suspensions were prepared.
The level of 3HTdR incorporation was then measured on a beta-scintillation counter.

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Positive control results:

EC3 = 12.9 % (positive)

Key result

Parameter:

SI

Value:

1.53

Test group / Remarks:

5%

Key result

Parameter:

SI

Value:

2.52

Test group / Remarks:

10%

Key result

Parameter:

SI

Value:

2.45

Test group / Remarks:

25%

No deaths occurred during the study period.

No symptoms of local toxicity at the ears of the animals and no systemic findings were observed during the study period.

The body weight of the animals, was within the range commonly recorded for animals of this strain and age.

 

Table 1: results

Vehicle: propylene glycol

Test item concentration % (w/v)	Group	Measurement DPM	Calculation			Result
			DPM-BG^a)	number of lymph nodes	DPM per lymph node^b^)	S.I.
---	BG I	30	---	---	---	---
---	BG II	15	---	---	---	---
---	1	1496	1474	8	184.2
5	2	2271	2249	8	281.1	1.53
10	3	3733	3711	8	463.8	2.52
25	4	3626	3604	8	450.4	2.45

BG =  Background (1 ml 5% trichloroacetic acid) in duplicate

1    =  Control Group

2-4=  Test Group

S.I. =  Stimulation Index

^a)   =  The mean value was taken from the figures BG I and BG II

^b)    =  Since the lymph nodes of the animals of a dose group were pooled, DPM/node was determined by dividing the measured value by the number of lymph nodes pooled

The EC3 value could not be calculated, since all S.I.´s are below 3.

Interpretation of results:

GHS criteria not met

Conclusions:

The test item D(-)alpha-Phenylglycine is not a skin sensitiser under the described conditions.

Executive summary:

In the study the test item D(-)alpha-Phenylglycine suspended in propylene glycol was assessed for its possible contact allergenic potential (OECD 429, GLP).

For this purpose a local lymph node assay was performed using test item concentrations of 5, 10, and 25%.

The animals did not show any clinical signs during the course of the study and no cases of mortality were observed.

In this study Stimulation Indices (S.I.) of 1.53, 2.52, and 2.45 were determined with the test item at concentrations of 5, 10, and 25% in propylene glycol, respectively.

The test item D(-)alpha-Phenylglycine is not a skin sensitiser in this assay.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The LLNA with the analogous substance phenylglycine and the QSAR showed no skin sensitising potential.
Therefore, it can be concluded that Phenylalanine does not have a skin sensitising potential.

Skin sensitization is the process following the epicutaneous application of a substance to the skin which results in an immunological response specific for this substance. Skin sensitisation is also called "delayed contact hypersensitivity", "contact hypersensitivity", "contact allergy" or "allergic contact dermatitis".

To behave as a contact allergen, a substance must penetrate into the skin and react with proteins. L-phenylalanine is a normal constituent of living cells as a free amino acid, bound to RNA and incorporated in proteins and peptides. Therfore, it is highly improbable that L-phenylalanine acts as a skin sensitizing agent.

Further, L-phenylalanine is used in parenteral nutrition, as a dietary supplement, in biochemical research, in cell culture media, as a feed additive, as an excipient in medicinal products and is a component found in skin and hair cosmetics.

 

Based on the available information, there is no human or animal data that indicates L-phenylalanine to be a skin sensitiser. Considering the extensive, widespread dermal exposure to L-phenylalanine in preparations repeatedly applied to the skin or being in contact with the skin, the absence of case reports of humans showing skin reactions is consistent with L-phenylalanine having a very low skin sensitisation potential.

 

Structural alerts for skin sensitisation were derived in a database which classified as strong or moderate sensitizers. These were the chemicals which would be classified according to the criteria of the Dangerous Substance Directive 67/548/EEC. For the identification of structural alerts, the chemicals were divided into groups, on the basis of reaction mechanisms or by empirical derivation: a) acylating agents; b) alkylating/arylating agents, c) "Michael" electrophiles and precursors; e) free radical generators; d) aldehydes and precursors, f) "thiol-exchange" agents; and g) others (empirical). Forty rules (structural alerts were identified from these group of chemicals. (see: de Silva et al, 1996; Klaschka and Voßmann, 1994).

 

L-Phenylalanine does not contain any of this structural alerts in its chemical structure.

 

In accordance with REACH Annex XI No. 8.3. column 1 the assessment of this endpoint shall comprise as the first step an assessment of the available human, animal and other data. These data reveal that in vivo testing is not required in accordance with REACH and animal welfare.

 

de Silva D. et al (1996): Alternative Methods for Skin Sensitisation testing. The report and recommendations of ECVAM Workshop 19. ATLA 24, 683 - 705

Klaschka F. und Voßmann D. (1994): Kontaktallergene.Erich-Schmidt-Verlag, Berlin

 

 

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Experience from the handling of L-phenylalanine in industrial and commercial surroundings strongly indicate that the substance is not sensitising via the respiratory route. Studies on this endpoint are not available.

Migrated from Short description of key information:

Experience from the handling of L-phenylalanine in industrial and commercial surroundings strongly indicate that the substance is not sensitising via the respiratory route.

Justification for classification or non-classification

L-Phenylalanine is considered as non sensitising and does not trigger respective classification.