3-phenyl-L-alanine

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

L-phenylalanine

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1993

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

not specified

GLP compliance:

not specified

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

S. typhimurium TA 98

Additional strain / cell type characteristics:

not specified

Species / strain / cell type:

S. typhimurium TA 100

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254 induced rat liver enzymes (S9 mix 3%)

Test concentrations with justification for top dose:

2.00 mg/ml

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: purified water (testing with UV-radiation), DMSO (test assays without UV-radiation)

Positive controls:

yes

Positive control substance:

2-nitrofluorene

sodium azide

other: 2-aminoanthracene

Details on test system and experimental conditions:

The test procedure of Maron and Ames was used and the mutagenicity factor for each sample was calculated by number of revertants of test substance/plate and number of spontaneous revertants/plate (rev./pl.).
In the case of testing with UV-irradiation the compounds were dissolved in 1000 ml purified water. The samples were irradiated either by low- or high-pressure vapor UV lamps with a fluence of 2500 J/m2. UV-irradiation doses up to 10 times the doses for physical disinfection were used. Dimethylsulfoxide (DMSO) was added as organic solvent to the irradiated samples. The water phase was extracted using evaporation equipment and the remaining DMSO-phase contained the organic components. Recovery rates above 90% for each compound were determined by HPLC. In parallel experiments the organic compounds were directly dissolved in DMSO for test assays without UV-irradiation. All samples were tested for mutagenicity with Ames-test.

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Positive controls validity:

valid

Conclusions:

L-phenylalanine was examined in Ames-test (bacterial strains TA 98 and TA 100) before and after UV-irradiation. Based on results in Ames test a mutagenic activity was not obtained for all L-phenylalanine samples, neither before nor after UV-irradiation.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 479 (Genetic Toxicology: In Vitro Sister Chromatid Exchange Assay in Mammalian Cells)

Deviations:

not specified

GLP compliance:

not specified

Type of assay:

sister chromatid exchange assay in mammalian cells

Target gene:

no data

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Test concentrations with justification for top dose:

2.00 mg/ml

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: purified water (testing with UV-radiation), DMSO (test assays without UV-radiation)

Positive controls:

yes

Positive control substance:

benzo(a)pyrene

other: Epichlorhydrine

Details on test system and experimental conditions:

For SCE-assay V79 Chinese hamster cells were grown in minimal essential medium (MEM) with Earle’s salts supplemented with 10% fetal calf serum and antibiotics. Cells were treated with the test substance for 2.5 h. Chromosome preparation and staining were performed according to standard protocols. Epichlorhydrine (1.0; 0.5; 0.25 mM) and benzo(a)pyrene (0.08; 0.04; 0.02 mM) were used as positive controls with and without metabolic activation. For each experimental data point 25 second division metaphases were scored and the mean values of SCEs per 22 chromosomes were evaluated.
In the case of testing with UV-irradiation the compounds were dissolved in 1000 ml purified water. The samples were irradiated either by low- or high-pressure vapor UV lamps with a fluence of 2500 J/m2. UV-irradiation doses up to 10 times the doses for physical disinfection were used. Dimethylsulfoxide (DMSO) was added as organic solvent to the irradiated samples. The water phase was extracted using evaporation equipment and the remaining DMSO-phase contained the organic components. Recovery rates above 90% for each compound were determined by HPLC. In parallel experiments the organic compounds were directly dissolved in DMSO for test assays without UV-irradiation. All samples were tested for mutagenicity with SCE-test.

Key result

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Positive controls validity:

valid

Conclusions:

L-phenylalanine was examined in a sister chromatid exchange (SCE)-test (V79 cells) before and after UV-irradiation. Based on results in the SCE-test a mutagenic activity was not obtained for all L-phenylalanine samples, neither before nor after UV-irradiation.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vitro:

In the key study L-phenylalanine was examined in the Ames-test (bacterial strains TA 98 and TA

100 of S. typhimurium) as well as the sister chromatid exchange (SCE)-test (V79 cells) before and after UV-irradiation.

Based on results in Ames- and SCE-test a mutagenic activity was not obtained for all

L-phenylalanine samples, neither before nor after UV-irradiation.

 

The Ames-test was performed with 2 strains of S. typhimurium but not with strains of E. coli, too. The SCE-test as a different in vitro method with a different mode of action for determining genetic toxicity was performed in addition. The test results can be regarded as valid under these conditions.

 

In one supporting study it was also observed that L-phenylalanine did not show mutagenic

activity.

In another supporting study the results indicate that orally administered phenylalanine even

inhibits the development of gastric cancers.

 

The negative result for genetic toxicity was foreseeable as L-phenylalanine is a naturally occurring essential amino acid. L-phenylalanine is a normal constituent in living cells occurring as a free amino acid, bound to RNA and incorporated in proteins and peptides. It is ingested daily in significant amounts. Therefore human exposure through food is orders of magnitude higher than the anticipated levels of exposure from the uses covered by this dossier. L-phenylalanine is present in significant amounts in human body fluids – e. g. human blood plasma (Cynober 2002) - as well as in human cells. It is a basic metabolite and building block of all living organisms and therefore a genotoxic/mutagenic potential could be excluded.

 

Cynober L (2002): Plasma Amino Acid Levels With a Note on Membrane Transport: Characteristics, Regulation, and Metabolic Significance.Nutrition 18 (9), 761-766

Justification for selection of genetic toxicity endpoint

Key study