(2R)-4-hydroxybutan-2-aminium (2S)-hydroxy(phenyl)acetate

Endpoint summary

Description of key information

Skin: not irritating
Eye irritation: irritating

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin irritation

The objective was to assess the skin corrosion and irritation potential of (R)-3 -Ammonium-1-hydroxybutyl (S)-mandelat. Using the currently available methods a single in vitro assay is not sufficient to cover the full range of skin irritating/corrosion potential including transport classification.

Therefore, three in vitro assays were proposed for this in vitro skin irritation and corrosion test strategy including transport classification: The Skin Corrosion Test (SCT), Skin Irritaion Test (SIT) and In vitro Membrane Barrier Test (Corrositex).

However, in the current case for (R)-3 -Ammonium-1 -hydroxybutyl (S)-mandelat the results derived with SIT and SCT alone were sufficient for a final assessment. Therefore further testing in Corrositex was waived.  

Skin Corrosion Test (SCT) and Skin Irritation Test (SIT): 

The potential of (R)-3 -Ammonium-1 -hydroxybutyl (S)-mandelat to cause dermal corrosion/irritation was assessed by a single topical application of ca. 25 µL bulk volume (about 12 mg) of the undiluted test substance to a reconstructed three dimensional human epidermis model (EpiDerm™). 

For the corrosion test two EpiDerm™ tissues were incubated with the test substance for 3 minutes and 1 hour, each. The irritation test was performed with three EpiDerm™ tissues, which were incubated with the test substance for 1 hour followed by a42-hours post-incubation period. 

Tissue destruction was determined by measuring the metabolic activity of the tissue after exposure/post-incubation using a colorimetric test. The reduction of mitochondrial dehydrogenase activity, measured by reduced formazan production after incubation with a tetrazolium salt (MTT) was chosen as endpoint. The formazan production of the test-substance treated epidermal tissues is compared to that of negative control tissues. The quotient of the values indicates the relative tissue viability. 

The following results were obtained in the EpiDerm™ skin corrosion/irritation test: 

The test substance is not able to reduce MTT directly. 

Corrosion test:

The mean viability of the test-substance treated tissues determined after an exposure period of 3 minutes was 92.9%, and it was 74.4% after an exposure period of 1 hour.

Irritation test:Two test runs were performed.

1^sttest run:

The mean viability of the test-substance treated tissues determined after an exposure period of 1 hourwith about 42 hours post-incubationwas 54.8%.

Due to non-concordant replicate measurements of the test-substance treated tissues (values for single tissues: 52.7%, 40.5% and 71.1%) and the borderline result another test run was performed to clarify the result.

2^ndtest run

The mean viability of the test-substance treated tissues determined after an exposure period of 1 hour with about 42 hours post-incubation was 68.1% (values for single tissues: 66.4%, 68.6% and 69.5%). All acceptance criteria were met.

  

Based on the observed results and applying the evaluation criteria it was concluded, that (R)-3 -Ammonium-1 -hydroxybutyl (S)-mandelat does not schow a skin irritation potential in the EpiDerm™in vitro skin irritation and corrosion test strategy including transport classification under the test conditions chosen. Hence, (R)-3 -Ammonium-1 -hydroxybutyl (S)-mandelat ist not assigned to a transport category.

 

Eye irritation

The objective was to assess the eye irritating potential of (R)-3 -Ammonium-1 -hydroxybutyl (S)-mandelat. Using the currently available methods a single in vitro assay is not sufficient to cover the full range of eye irritating potential. Therefore, two in vitro assays were part of this in vitro eye irritation test strategy: The Bovine Corneal Opacity and Permeability Test (BCOP Test) and EpiOcular Eye Irritation Test.

 

BCOP

The potential of (R)-3 -Ammonium-1 -hydroxybutyl (S)-mandelat to cause ocular irritation or serious damage to the eyes was assessed by a single topical application of 750 µL of a 20% test-substance preparation to theepithelial surface of isolated bovine corneas. 

Three corneas were treated with the test-substance preparation foran exposure period of 4 hours. 

In addition to the test substance a negative control (NC; de-ionized water) and a positive control (PC; 20% imidazole in de-ionized water) were applied to three corneas each. 

Corneal opacity was measured quantitatively as the amount of light transmitted through the cornea. Permeability was measured quantitatively as the amount of sodium fluorescein dye that passes across the full thickness of the cornea. Both measurements were used to calculate an In Vitro Irritancy Score of the test substance.

EpiOcular  

The potential of (R)-3 -Ammonium-1 -hydroxybutyl (S)-mandelat to cause ocular irritation was assessed by a single topical application of ca. 50 µL bulk volume (about 18 mg) of the undiluted test substance to a reconstructed three dimensional human cornea model (EpiOcular™).  

Two EpiOcular™ tissues were incubated with the test substance for 6 hours followed by an 18-hours post-incubation period.  

Tissue destruction was determined by measuring the metabolic activity of the tissue after exposure/post-incubation using a colorimetric test. The reduction of mitochondrial dehydrogenase activity, measured by reduced formazan production after incubation with a tetrazolium salt (MTT) was chosen as endpoint. The formazan production of the test-substance treated epidermal tissues is compared to that of negative control tissues. The ratio of the values indicates the relative tissue viability.  

The following results were obtained in the EpiOcular™ eye irritation assay: The test substance is not able to reduce MTT directly.

Test Method	Test Result	Test Evaluation	Evaluation Test Strategy
BCOP Test	The mean IVIS of the test-substance treated corneas was 0.3.	Not identified as corrosive or severe irritant.	Ocular irritant
EpiOcular	Mean viability of the test-substance treated tissues was 3.5%.	Irritant

 

The mean viability of the test-substance treated tissues was 3.5%.

Based on the results for BCOP and EpiOcular Test and applying the evaluation criteria, (R)-3 -Ammonium-1 -hydroxybutyl (S)-mandelat shows an eye irttitation potential in the in vitro eye irritation test strategy under the test conditions chosen.

Justification for selection of skin irritation / corrosion endpoint:
Only available study

Justification for selection of eye irritation endpoint:
Only available study

Effects on eye irritation: irritating

Justification for classification or non-classification

Based on the available studies data on skin and eye irritating properties the test item would have to be classified as not irritating to skin but as eye irritant Cat. 2 (H319) according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No 1272/2008.