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Description of key information

Two in vitro tests were perfomred to assess the skin irritation / corrosion potential of alpha-Lipoic acid.

The Bovine Cornea Opacity and Permeability assay was perfomred to assess the eye irritation / corrosion potential of alpha-Lipoic acid.

On Reconstructed Human Epidermis (RHE, EpiDerm) the test item showed no corrosive but irritating effects.

With the the BCOP-assay no predictiction can be made about effects of the test item on the eyes.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Referenceopen allclose all

Endpoint:
skin corrosion: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-01-04 - 2017-02-23
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 431 (In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method)
Version / remarks:
2016-07-29
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Test system:
human skin model
Source species:
human
Cell type:
other: NHEC: normal human-derived epidermal keratinocytes
Justification for test system used:
The EpiDerm(TM) Skin Model is a well established organotypic, three-dimensional model of the human epidermis and is used for in vitro experiments many years. It is known for its similaryty to huaman skin.
Vehicle:
water
Details on test system:
The test was carried out with the reconstituted three-dimensional human skin model EpiDerm(TM) (MatTek). This skin model consists of normal human epidermal keratinocytes (NHEK) which have been cultured to form a multilayered, highly differentiated model of the human epidermis. The NHEK are cultured on chemically modified, collagen-coated cell culture inserts (Millicell(R)). The EpiDerm(TM) epidermis model exhibits in vivo-like morphological and growth characteristics which are uniform and highly reproducible. It consists of organised basal, spinous and granular layers and a multi-layered stratum corneum analogous to patterns found in vivo.
Control samples:
yes, concurrent negative control
yes, concurrent positive control
Amount/concentration applied:
Negative control: 50 µL distilled Water
Positive control: 50 µL 8 N KOH
Test Item: 25 mg + 25 µL H2O
Duration of treatment / exposure:
3 min; 60 min
Number of replicates:
4 per dose group
2 repliocates for each treatment period
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
3 min
Value:
ca. 97.5
Vehicle controls valid:
not examined
Negative controls valid:
yes
Positive controls valid:
yes
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
60 min
Value:
ca. 77.5
Vehicle controls valid:
not examined
Negative controls valid:
yes
Positive controls valid:
yes
Interpretation of results:
other: non-corrosive
Conclusions:
In the study under the given conditions the test item showed no corrosive effects. The test item is classified as "non-corrosive".
Executive summary:

In the present study the skin corrosivity of Thioctic Acid was analysed. Since corrosive chemicals are cytotoxic after a short tim exposure to the stratum corneum of the epidermis the cytotoxic effects of the test item on EpiDerm(TM), a reconstituted three-dimensional human epidermis model, were determined. Hereby, the test item was applied topically. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogensase activity measured by formazan production from MTT after a 3 min and 60 min exposure period and compared to those of the concurrent negative controls.

Endpoint:
skin irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-03-17 - 2017-05-26
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)
Version / remarks:
2015-07-06
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)
Version / remarks:
2012-07-06
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Test system:
human skin model
Source species:
human
Cell type:
other: NHEC: normal human-derived epidermal keratinocytes
Justification for test system used:
This test uses the EpiDerm™ reconstructed human epidermis model (MatTek) which consists of normal human epidermal keratinocytes (NHEK) and therefore represents in vitro the target organ of the species of interest and closely mimics the biochemical and physiological properties of the upper parts of the human, i.e. the epidermis.
Vehicle:
physiological saline
Remarks:
DPBS: Dulbecco’s phosphate buffered saline
Details on test system:
The test was carried out with the reconstituted three-dimensional human skin model EpiDerm(TM) (MatTek). This skin model consists of normal human epidermal keratinocytes (NHEK) which have been cultured to form a multilayered, highly differentiated model of the human epidermis. The NHEK are cultured on chemically modified, collagen-coated cell culture inserts (Millicell(R)). The EpiDerm(TM) epidermis model exhibits in vivo-like morphological and growth characteristics which are uniform and highly reproducible. It consists of organised basal, spinous and granular layers and a multi-layered stratum corneum analogous to patterns found in vivo.
Control samples:
yes, concurrent negative control
yes, concurrent positive control
Amount/concentration applied:
Negative control: 30 µL DPBS
Positive Control: 30 µL 5% SDS solution
Test Item: 25 mg + 25 µL DPBS
Duration of treatment / exposure:
60 min (35 min in the incubator -> 37 °C, 5 % CO2; 25 min under sterile flow)
Duration of post-treatment incubation (if applicable):
42 h (24 h in the incubator -> 37 °C, 5 % CO2, 95 % humidity; 18 h under same conditions, but in new wells with fresh assay medium)
Number of replicates:
3
Irritation / corrosion parameter:
% tissue viability
Value:
ca. 22
Vehicle controls valid:
not examined
Negative controls valid:
yes
Positive controls valid:
yes
Interpretation of results:
Category 2 (irritant) based on GHS criteria
Conclusions:
In this study under the given conditions the test item showed irritant effects. The relative mean tissue viability after 60 min of exposure and 42 h post-incubation was ≤ 50%. The test item is therefore classified as “irritant” in accordance with UN GHS “Category 2”.
Executive summary:

In the present study the skin irritant potential of Thioctic Acid was analysed. The EpiDerm™-Standard Model (EPI-200™), a reconstituted three-dimensional human epidermis model, was used as a replacement for the Draize Skin Irritation Test (OECD TG 404, [7]) to distinguish between UN GHS “Category 2” skin irritating test substances and not categorized test substances (“No Category”) which may be considered as non-irritant. Hereby, the test item was applied topically. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazan production from MTT after a 60 min exposure and 42 h post-incubation period and compared to those of the concurrent negative controls.

The test item showed irritant effects. The mean relative tissue viability (% negative control) was ≤ 50% (22%) after 60 min treatment and 42 h post-incubation.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (irritating)

Eye irritation

Link to relevant study records
Reference
Endpoint:
eye irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-01-20 - 2017-03-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)
Deviations:
yes
Remarks:
Phenol red free RPMI 1640 medium instead of phenol red free EMEM
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Species:
cattle
Strain:
not specified
Details on test animals or tissues and environmental conditions:
The Assay uses isolated corneas obtained as a by-product from animals freshly slaughtered.
Vehicle:
physiological saline
Controls:
yes, concurrent positive control
yes, concurrent negative control
Amount / concentration applied:
Negative control: physiological saline 0.9 % NaCl
Positive control: Imidazole 20 % in physiological saline 0.9 % NaCl
Test item: 20 % suspended in physiological saline 0.9 % NaCl
Duration of treatment / exposure:
4 h
Number of animals or in vitro replicates:
3 corneas in each group
Irritation parameter:
in vitro irritation score
Value:
ca. 36.57
Vehicle controls valid:
not examined
Negative controls valid:
yes
Remarks:
IVIS: 1.63
Positive controls valid:
yes
Remarks:
IVIS: 122.97
Irritation parameter:
cornea opacity score
Value:
ca. 36.54
Vehicle controls valid:
not examined
Remarks:
Corrected opacity: 0
Negative controls valid:
yes
Remarks:
Corrected opacity: 101
Positive controls valid:
yes
Irritation parameter:
fluorescein leakage
Remarks:
Corrected OD490
Value:
ca. 0.002
Negative controls valid:
yes
Positive controls valid:
yes
Remarks:
1.462
Interpretation of results:
GHS criteria not met
Conclusions:
No prediction can be made regarding the classification of the test substance Thioctic Acid to the evaluation criteria. Furhter testing in another suitable method is required.
Executive summary:

The eye irritancy potencial of Thioctic Acid was investigated in the bovine corneal opacity and permeability assay.

The test item was suspended with physiologicalsaline 0.9 % to give a 20 % concentration.

Mean in vitro irritation score: 36.57

Classification: No prediction can be made

The in vitro irritation score obtained with the positive control fell witin the two standard deviations of the current historical mean and therefore this assay is concidered to be valid.

The negative control responses should result in opacity and permeability values that are less the establisched upper limits for background bovine corneas treated with the respective negative control.

Additional information

Justification for classification or non-classification

The relative mean tissue viability after 60 min of exposure and 42 h post-incubation was ≤ 50%. According to the CLP regulation the test item is therefore classified as “skin irritant" (UN GHS “Category 2”).

The IVIS obtained by the PCOP assay is 36.57. An IVIS between 3 and 55 can't be used for classification.

As alpha-Lipoic acid is classified as "skin irritant" (UN GHS "Category 2") it can be concluded it also may cause serious eye irritations (UN GHS "Category 2").