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EC number: 200-568-1 | CAS number: 63-91-2
L-Phenylalanine is neither irritating or corrosive to skin nor irritating to eyes as well as to the respiratory system.
The EpiDermTM model was employed.
Three tissues were used for each treatment and concurrent control groups. The optical density (OD) was determined by using the MTT (3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide, Thiazolyl blue) reduction assay and expressed as relative percentage of viability of the negative control-treated tissues.
L-Phenylalanine was applied topically as solid test item to the model skin surface, which was moistened with phosphate buffered saline. Dulbecco’s phosphate buffered saline (D-PBS) was used as the negative control. 5% aqueous sodium dodecyl sulphate (SDS) was used as the positive reference item.
The mea n viability of cells exposed to L-Phenylalanine was 103.1% of the negative controls and, hence, was well above the cut-off percentage cell viability value that distinguishes irritant from non-irritant test items of > 50%. L-Phenylalanine was considered to be non-cytotoxic and predicted to be nonirritant to skin. The mean optical density (OD) of the negative control of 3 tissues was 2.160 and was well within the acceptable range of ≥ 1.0 to ≤ 2.5. The viability of cells treated with the positive reference item, 5% SDS, was 3.1% of the negative control and fulfilled the acceptance criteria of < 20%. The standard deviation of all triplicates determined was below the limit of acceptance of 18%. Hence, all acceptance criteria were fulfilled. Conclusion: Under the present test conditions, L-Phenylalanine tested at an exposure time of 60 minutes and a 42-hour post-treatment incubation period, was non-cytotoxic and, hence, was considered to be non-irritant to skin in an experiment employing an artificial three-dimensional model of human skin.
The current ICCVAM recommended protocol for which HET-CAM is recommended as a screening test to identify non-labelled ocular irritants uses an analysis method (i.e., the Irritation Score IS(A)) which is based on development of each of the three
HET-CAM endpoints at fixed time intervals of 0.5, 2, and 5 minutes (Table 1; Lüpke 1985).
The numerical time-dependent scores for lysis, haemorrhage, and coagulation (Table 2) are summed to give a single numerical value indicating the irritation potential of the test substance on a scale with a maximum value of 21.
Table 1: Scoring scheme for irritation testing
Table 2: Classification of cumulative scores
0 - 0.9
1 - 4.9
5 - 8.9
9 - 21
Criteria for an acceptable test
The HET-CAM assay is considered acceptable if the negative and positive controls each induce a response that falls within the classification of nonirritating and severely irritating, respectively. Historical control studies indicate that using 0.9% NaCl, as a negative control, the IS value was 0.0 (35 studies in the time period between 2010 and 2012). Historical control studies demonstrate that using 1% SDS and 0.1 N NaOH as positive controls results in IS values of approximately 8 to 12 or 17 to 19, respectively.
Lüpke, N. P., 1985: Hen's egg chorioallantoic membrane test for irritation potential Fd. Chem. Toxic. Vol. 23, No. 2, pp. 287 - 291
ICCVAM. 2010: ICCVAM-Recommended Test Method Protocol: Hen’s Egg Test - Chorioallantoic Membrane (HET-CAM) Test Method. NIH Publication No: 10-7553, published 2010.
The dermal irritant potential of L-phenylalanine was assessed in a GLP gudeline study according to OECD 439 (three-dimensional reconstructed human epidermis model) by application of the substance to the test system. L-Phenylalanine did not show to be irritating to the skin and is not classified as irritating or corrosive to human skin.
The eye irritant potential of L-phenylalanine was assessed in an in vitro GLP study using fertile chicken eggs (HET-CAM test).
There are no data available which indicate that L-phenylalanine is irritant to the respiratory system.
Justification for selection of skin irritation / corrosion endpoint:
Justification for selection of eye irritation endpoint:
L-Phenylalanine does not show any irritating or corrosive properties towards both the skin and the eyes. Thus classification is not required.
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