5-(dithiolan-3-yl)valeric acid

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

No genotoxicity and mutagenicity of alpha-lipoic acid was observed in bacteria (AMES-test) V79 Chinese Hamster Fibroblasts (HPRT-test, chromosomal aberration study).

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1996-04-22 - 1996-07-08

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

1983-05-26

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Species / strain / cell type:

S. typhimurium TA 97

Metabolic activation:

with and without

Metabolic activation system:

S9-Mix

Vehicle / solvent:

DMSO

Untreated negative controls:

yes

Remarks:

Solvent treated (DMSO)

Positive controls:

yes

Positive control substance:

benzo(a)pyrene

other: 2-Aminoanthracene

Positive controls:

yes

Positive control substance:

cumene hydroperoxide

other: Benzo(a)pyren-4,5-oxide; TA1535; TA1537, TA100, TA97; TA98; w/o metabolic activation

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not examined

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not examined

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 97

Metabolic activation:

with

Genotoxicity:

other: extremely weak

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not examined

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 97

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not examined

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not examined

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not examined

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not examined

Untreated negative controls validity:

valid

Positive controls validity:

valid

Conclusions:

Alpha-Lipoic acid is not mutagenic in the Salmonella typhimurium standard strains TA 100, TA98, TA1535, TA1537 and TA 102 with and w/o S-9 mix.
The observed extremely weak effect of alpha-Lipoic acid only with metabolic actication is lower than it is with physiological endigenous compounds like L-systeine and glutathione.
Alpha-Lipoic acid is considered negative in the Salmonella Typhimurium Reverse Mutation Assay

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1996-07-08 - 1996-10-31

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Version / remarks:

May 1995

GLP compliance:

yes

Type of assay:

other: chormosomal aberrations

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Remarks:

A2

Metabolic activation:

with and without

Metabolic activation system:

S9-Mix (Aroclor 1254-induced Wistar rats)

Test concentrations with justification for top dose:

5000 µg/mL, according to relevant international test guidelines.
Aim: approx. 50 % reduction of mitotic index coompared do negative controls

Vehicle / solvent:

Dimethyl sulphoxide (DMSO), 1 %

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

Positive controls:

yes

Positive control substance:

cyclophosphamide

ethylmethanesulphonate

Details on test system and experimental conditions:

- two independant experiments
- 18 h and 28 h treatment

Statistics:

Chi-spuare test

Key result

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

reduced cell number and mitotic index at higher concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

not determinable

Conclusions:

Under the conditions described solutions from Thioctic Acid, Racemate w/o as well as with a metabolic activation system are considered not to induce structural and numerical chromosomal aberrations in V79 Chinese hamster fibroblasts in vitro.

Executive summary:

Chromosomal aberrations:

No statistically significant, biological relevant and reproducible increase in the incidence of cells with structural chromosomal aberrations was present for any experimental group treated with solutions of Thioctic acid compared to negative control groups during both experiments. This was true for treatment w/o exogenous metabolic activation and with exogenous metabolic activation, as well as for both teh 18 h sampling time and the 28 h sampling time.

In the positive control groups treated with ethyl methane sulphonate or cyclophosphamide, predominantly distinct and statistically significant increases in the number of metaphases with structural cromosomal aberations occured.

No increase in polyploidy considered to be related to the treatment with solutions from Thioctic Acid, Racemate, or with the positive control substances, ethyl methyl sulphonate or cyclophosphamide, discernible.

Reference 3

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1998-02-18 - 1998-04-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

Deviations:

no

GLP compliance:

yes

Type of assay:

other: in vitro gene mutation study in mamalian cells

Target gene:

hypoxantine-guanine phosphoribosyl transferase (hprt)

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Metabolic activation system:

S9-Mix from liver of Aroclor 1254-induced Sprague Dawley rats

Test concentrations with justification for top dose:

alpha-Lipoic acid: 156 - 5000 µg/mL -> 5000 µg/mL is maximum concentration according to current guidelines, precipitaion was observed in this solutions.

Vehicle / solvent:

dimethylsulfoxide (DMSO)

Untreated negative controls:

yes

Remarks:

with and w/o metabolic activation

Negative solvent / vehicle controls:

yes

Remarks:

DMSO, 1 %; with and w/o metabolic activation

Positive controls:

yes

Positive control substance:

9,10-dimethylbenzanthracene

ethylmethanesulphonate

Details on test system and experimental conditions:

Two independent experiments.
treatment: 4 h (with and w/o metabolic activation) => according to guideline incubation time of 3 - 6 h is effecticve to induce mutation at the HPRT-gene
Two parallel cultures in each experimental group.
Selection of mutatants: Preparation of 6 petri dishes from each culture.

Evaluation criteria:

If a test substance produced neither a biologically relevant and reproducible positive response at any test point nor a concentration related and biologically relevant increase in teh mutant frequency compared to the respective negative control group, it is considered as non-mutagenic in this system.

Key result

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Conclusions:

Under the conditions described, solutions from Thioctic Acid up to concentration of 5000 µg/mL w/o as well as with a metabolic activation system are considered to induce no gene mutations at the HPRT gene in V79 Chinese hamster fibroblasts in vitro.

Executive summary:

General:

Two independent experiments were carried out. The treatment interval was 4 h in test parts with and w/o metabolic activation. After the treatment the cells were allowed for expression of a possible treatment induced mutant phenotype for 7 d. Then cells were seeded for selection of mutants in a 6-tihioguanine containing mediumg and incubated for further 7 days. in each experimental group two parallel cultures were used. for selection of mutants form each cell culture 6 petri dishes were prepared.

Results:

The pH- and osmolality values determined for concentrations of 5000 µg/mL Tioctic Acid with and w/o metabolic activation were considered acceptable for in vitro tests using cultivated mammalian cells w/o going the risk to induces artificial findings.

During both experiments the mutant frequency was not influenced by treatment with the test subatance with or w/o metabolic activation up to a maximum concentration of 5000 µg/mL.

The positive control groups, treated with ethyl methane sulphonate (EMS) or 9,10-dimethyl-1,2 -benzanthracene (DMBA), predominantly predominantly distinct increases in the mutant frequency occured.

Cytotoxicity:

During the main trials only in the 2nd experiment a moderate cytotoxic effect was noted with a decrease of the cell number at the end of the treatment period as compared to concurrent negative controls. This only was present at the highest concentration of the test substance of 5000 µg/mL, but observed in both parts (with and w/o metabolic activation).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

No genotoxicity of alpha-lipoic acid was observed in mice (in vivo micronucleus test).

Link to relevant study records

Reference

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1995-09-19 - 1995-09-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Study owner prepared study while seeking authorisation of the substance as active incredient for medical treatment.

Qualifier:

according to guideline

Guideline:

EU Method B.12 (Mutagenicity - In Vivo Mammalian Erythrocyte Micronucleus Test)

GLP compliance:

yes

Type of assay:

other: in vivo micronucleus test

Species:

mouse

Strain:

NMRI

Sex:

male/female

Details on test animals or test system and environmental conditions:

Caging: Macrolon cages, type II

Animals per cage: 1

Bedding: Animal bedding softwood garnulation HW 300/500W

Diet: Standard diet ad libitum

Water: ad libitum

Room temperature: 21.0 - 22.0 °C
Relative humidity: 48 - 52 %
Room lighting: 6:00 - 18:00 (cet) artificial lighting
18:00 - 6:00 (cet) darknes

Route of administration:

oral: gavage

Vehicle:

propylene glycol

Frequency of treatment:

single administration

Post exposure period:

24 h and 48 h

Dose / conc.:

825 mg/kg bw/day (nominal)

No. of animals per sex per dose:

Negative control: 12 m + 12 f
Positive control: 6 m + 6 f
Test material group: 19 m + 17 f

Control animals:

yes

Positive control(s):

Cyclophosphamid

Tissues and cell types examined:

Bone marrow cells from both femurs.
Polychromatic erythrocytes

Details of tissue and slide preparation:

Bone marrow was suspended in approx. 1.5 ml FCS and centrifuged at 180 g for 5 min.
Supernatand was discarded and cells were suspended in FCS.
Small drop of this suspension was smeared on a slide and dried overnight.

Statistics:

POISSON test

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

ten test material group animals died

Vehicle controls validity:

valid

Negative controls validity:

not examined

Positive controls validity:

valid

Conclusions:

Thioctic acid, racemate, at 825 mg/kg body weight (males and females, single oral administration) is non-genotoxic in the mouse micronucleus test under the described conditions.

Executive summary:

Ten (10) test mateial group animals died.

After a singele oral admission of the test material à 825 mg/kg b. w. no statistically significant test material-related increase im micronucleated PCEs was observed in both, male and female animals, respectively males and females combined, when compared with corresponding negative control group animals at 24 h or 48 h after administration. No reduction in PCE/NCE ratio was present in test material group animals, when compared to the corresponding control group animals.

The positive control group animals, wich recieved cyclophosphamide, exhibited a significant increase in the number of micronucleated polychromatic erythrocytes and thus validated the test system.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Justification for classification or non-classification

According to the GHS regulation alpha-Lipoic acid is not classified as genotoxic or mutagenic.