2-phosphonobutane-1,2,4-tricarboxylic acid

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2021

Report date:

2021

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

Ninth Addendum to OECD Guidelines for Testing of Chemicals, Section 4, No. 471: Bacterial Reverse Mutation Test, corrected June 26, 2020

Principles of method if other than guideline:

This study was performed to investigate the potential of Tetrasodium hydrogen 2-phosphonato-butane-1,2,4-tricarboxylate to induce gene mutations according to the plate incorporation test (experiment I) and the pre-incubation test (experiment II) using the Salmonella typhimurium strains TA 1535, TA 1537, TA 98, TA 100, and the Escherichia coli strain WP2 uvrA. The study protocol followed OECD TG 471.
The assay was performed in two independent experiments both with and without liver microsomal activation. Each concentration, including the controls, was tested in triplicate.

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate

EC Number:

266-442-3

EC Name:

Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate

Cas Number:

66669-53-2

Molecular formula:

C7H7Na4O9P

IUPAC Name:

hydrogen tetrasodium 2-phosphonatobutane-1,2,4-tricarboxylate

Test material form:

solid

Details on test material:

Alternative name: Bayhibit S
Batch number: CH19/09
Empirical formula: C7H7O9P •4 Na
Molecular mass: 358.1 g/mol

Method

Species / strain

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Details on mammalian cell type (if applicable):

The Salmonella typhimurium histidine (his) and the Escherichia coli tryptophan (trp) reversion system measures his- → his+ and trp- → trp+ reversions, respectively. The Salmonella typhimurium and Escherichia coli strains are constructed to differentiate between base pair (TA 1535, TA 100, and WP2 uvrA) and frameshift (TA 1537, TA 98) mutations.

Metabolic activation:

with and without

Test concentrations with justification for top dose:

The test item was tested at the following concentrations:
Pre-Experiment/Experiment I: 3; 10; 33; 100; 333; 1000; 2500; and 5000 μg/plate
Experiment II: 33; 100; 333; 1000; 2500; and 5000 μg/plate
No precipitation of the test item occurred up to the highest investigated dose

Dose Selection
In the pre-experiment the concentration range of the test item was 3 – 5000 μg/plate. The pre-experiment is reported as experiment I. Since no toxic effects were observed 5000 μg/plate were chosen as maximal concentration. The concentration range included two logarithmic decades.
The following concentrations were tested in experiment II:
33; 100; 333; 1000; 2500; and 5000 μg/plate

Vehicle / solvent:

Deionized water or DMSO

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

not specified

Positive controls:

yes

Positive control substance:

sodium azide

methylmethanesulfonate

other: 4-nitro-o-phenylene-diamine, 4-NOPD 2-aminoanthracene, 2-AA

Details on test system and experimental conditions:

Experimental Design and Study Conduct
Pre-Experiment for Toxicity
To evaluate the toxicity of the test item a pre-experiment was performed with all strains used. Eight concentrations were tested for toxicity and mutation induction with each 3 plates. The experimental conditions in this pre-experiment were the same as described for the experiment I below (plate incorporation test).

Toxicity of the test item results in a reduction in the number of spontaneous revertants (below a factor of 0.5) or a clearing of the bacterial background lawn.
The pre-experiment is reported as main experiment I since the acceptance criteria are met.

Dose Selection
In the pre-experiment the concentration range of the test item was 3 – 5000 μg/plate. The pre-experiment is reported as experiment I. Since no toxic effects were observed 5000 μg/plate were chosen as maximal concentration. The concentration range included two logarithmic decades.
The following concentrations were tested in experiment II:
33; 100; 333; 1000; 2500; and 5000 μg/plate

Experimental Performance
For each strain and dose level, including the controls, three plates were used.
Experiment I (Plate Incorporation)
The following materials were mixed in a test tube and poured onto the selective agar plates:
100 μL Test solution at each dose level (solvent or reference mutagen solution (positive control)),
500 μL S9 mix (for test with metabolic activation) or S9 mix substitution buffer (for test without metabolic activation),
100 μL Bacteria suspension,
2000 μL Overlay agar

Experiment II (Pre-Incubation)
The following materials were mixed in a test tube and incubated at 37 °C ± 1.5 °C for 60 minutes.
100 μL Test solution at each dose level (solvent or reference mutagen solution (positive control)),
500 μL S9 mix (for test with metabolic activation) or S9 mix substitution buffer (for test without metabolic activation), 100 μL Bacteria suspension
After pre-incubation 2.0 mL overlay agar (45°C) was added to each tube.
The mixture was poured on minimal agar plates. After solidification, the plates were incubated upside down for at least 48 hours at 37 °C ± 1.5 °C in the dark.
In parallel to each test a sterile control of the test item was performed and documented in the raw data. Therefore, 100 μL of the stock solution, 500 μL S9 mix / S9 mix substitution buffer were mixed with 2.0 mL overlay agar and poured on minimal agar plates.

Rationale for test conditions:

Pre-Experiment for Toxicity

To evaluate the toxicity of the test item a pre-experiment was performed with all strains used. Eight concentrations were tested for toxicity and mutation induction with each 3 plates. The experimental conditions in this pre-experiment were the same as described for the experiment I below (plate incorporation test).

Toxicity of the test item results in a reduction in the number of spontaneous revertants (below a factor of 0.5) or a clearing of the bacterial background lawn.
The pre-experiment is reported as main experiment I since the acceptance criteria are met.

Dose Selection
In the pre-experiment the concentration range of the test item was 3 – 5000 μg/plate. The pre-experiment is reported as experiment I. Since no toxic effects were observed 5000 μg/plate were chosen as maximal concentration. The concentration range included two logarithmic decades.

The following concentrations were tested in experiment II:
33; 100; 333; 1000; 2500; and 5000 μg/plate

Evaluation criteria:

Acceptability of the Assay

The Salmonella typhimurium and Escherichia coli reverse mutation assay is considered acceptable if it meets the following criteria:

• regular background growth in the negative and solvent control;
• the spontaneous reversion rates in the negative and solvent control are in the range of our historical data;
• the positive control substances should produce an increase above the threshold of twofold (strains TA 98, TA 100, and WP2 uvrA) or threefold (strains TA 1535 and TA 1537) the colony count of the corresponding solvent control;
• a minimum of five analysable dose levels should be present with at least three dose levels showing no signs of toxic effects, evident as a reduction in the number of revertants below the indication factor of 0.5.

Current historical control data are available.

Evaluation of Results
A test item is considered as a mutagen if a biologically relevant increase in the number of revertants of twofold or above (strains TA 98, TA 100, and WP2 uvrA) or threefold or above (strains TA 1535 and TA 1537) the spontaneous mutation rate of the corresponding solvent control is observed.

A dose dependent increase is considered biologically relevant if the threshold is reached or exceeded at more than one concentration.

An increase of revertant colonies equal or above the threshold at only one concentration is judged as biologically relevant if reproduced in an independent second experiment.

A dose dependent increase in the number of revertant colonies below the threshold is regarded as an indication of a mutagenic potential if reproduced in an independent second experiment. However, whenever the colony counts remain within the historical range of negative and solvent controls such an increase is not considered biologically relevant.

Statistics:

Biometry

According to the OECD guideline 471, a statistical analysis of the data is not mandatory.

Results and discussion

Test results

Key result

Species / strain:

other: Bacterial strains TA 1535, TA 1537, TA 98, TA 100, and WP2 uvrA

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

Additional information on results:

No precipitation of the test item occurred up to the highest investigated dose.
The plates incubated with the test item showed normal background growth up to 5000 μg/plate with and without S9 mix in all strains used.

No toxic effects, evident as a reduction in the number of revertants (below the indication factor of 0.5), occurred in all strains with and without metabolic activation.

No substantial increase in revertant colony numbers of any of the five tester strains was observed following treatment with Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate at any dose level, neither in the presence nor absence of metabolic activation (S9 mix). There was also no tendency of higher mutation rates with increasing concentrations in the range below the generally acknowledged border of biological relevance.

Appropriate reference mutagens were used as positive controls and showed a distinct increase of induced revertant colonies.

Any other information on results incl. tables

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.

Applicant's summary and conclusion

Conclusions:

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.

Therefore, Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.

Executive summary:

The test item Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate was assessed for its potential to induce gene mutations according to the plate incorporation test (experiment I) and the pre-incubation test (experiment II) using Salmonella typhimurium strains TA 1535, TA 1537, TA 98, TA 100, and the Escherichia coli strain WP2 uvrA.

The assay was performed in two independent experiments both with and without liver microsomal activation. Each concentration and the controls were tested in triplicate. The test item was tested at the following concentrations:
Pre-Experiment/Experiment I: 3; 10; 33; 100; 333; 1000; 2500; and 5000 μg/plate
Experiment II: 33; 100; 333; 1000; 2500; and 5000 μg/plate

No precipitation of the test item occurred up to the highest investigated dose.
The plates incubated with the test item showed normal background growth up to 5000 μg/plate with and without S9 mix in all strains used.

No toxic effects, evident as a reduction in the number of revertants (below the indication factor of 0.5), occurred in the test groups with and without metabolic activation.

No substantial increase in revertant colony numbers of any of the five tester strains was observed following treatment with Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate at any concentration level, neither in the presence nor absence of metabolic activation (S9 mix). There was also no tendency of higher mutation rates with increasing concentrations in the range below the generally acknowledged border of biological relevance.

Appropriate reference mutagens were used as positive controls. They showed a distinct in-crease in induced revertant colonies.