di-p-tolyl(2,4,6-trimethylbenzoyl)phosphine oxide

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro cytogenicity / micronucleus study

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2023

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2023

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: Commission Regulation (EU) 2017/735 amending Regulation (EC) No. 440/2008, EU Method B.49: “In Vitro Mammalian Cell Micronucleus Test”, adopted 14. Feb. 2017

Deviations:

not specified

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 487 (In vitro Mammalian Cell Micronucleus Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

in vitro mammalian cell micronucleus test

Test material

Test material information

Constituent 1

Reference substance name:

[bis(4-methylphenyl)phosphoroso](2,4,6-trimethylphenyl)methanone

EC Number:

884-585-5

Cas Number:

270586-78-2

Molecular formula:

C24H25O2P

IUPAC Name:

[bis(4-methylphenyl)phosphoroso](2,4,6-trimethylphenyl)methanone

Method

Species / strain

Species / strain / cell type:

lymphocytes:

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

yes

Positive controls:

yes

Positive control substance:

mitomycin C

Results and discussion

Test results

Species / strain:

lymphocytes: cultivated human lymphocytes

Metabolic activation:

with and without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

True negative controls validity:

valid

Positive controls validity:

valid

Applicant's summary and conclusion

Conclusions:

In conclusion, under the experimental conditions reported, (di-p-tolylphosphoryl)(mesityl)methanone is able to induce the formation of micronuclei in hu-man lymphocytes in vitro.
The result of the micronucleus test with the test item (di-p-tolylphosphoryl)(mesityl)methanone is considered as “positive” under the conditions of the test.

Executive summary:

This study was performed to assess the potential of (di-p-tolylphosphoryl)(mesityl)methanone to induce formation of micronuclei in human lym-phocytes cultured in vitro in absence and presence of an exogenous metabolic activation system (liver S9 mix from male rats, treated with Phenobarbital/5,6-Benzoflavone).
For the analysis of the genotoxic potential of the test item, 6 concentrations were tested in duplicate cultures of human lymphocytes in one valid experiment with metabolic activa-tion. Three concentrations were chosen for evaluation of genotoxicity each. A minimum of 1000 binucleated cells were evaluated per culture and were scored for the presence of micronuclei. The recorded values were compared with a negative control (solvent only, in this case ethanol 1% v/v).
Detailed data is presented in annex 4 (pre-experiment: page 37ff; pre-experiment II with-out metabolic activation: page 41ff, experiment I with metabolic activation: page 43ff).
The study is considered acceptable: micronucleus induction of the solvent controls was in the range of the historical control data/literature data. The positive control compounds Mitomycin C (0.3 µg/mL), CPA (15 µg/mL and 10 µg/mL) showed distinct increases in the number of binucleated cells with micronuclei.
In pre-experiment II without metabolic activation, turbidity of the test item was visible at the two highest test item concentrations (0.25 mg/mL and 0.13 mg/mL). At the two lower test item concentrations (0.06 mg/mL and 0.03 mg/mL) extreme cytotoxicity was observed. An evaluation of these concentrations was not possible. Since only two further test item con-centrations were available, an evaluation of micronuclei according to OECD 487 was not possible since < 3 test item concentrations were suitable. For that reason, only the con-trols were evaluated for micronuclei to show the validity of this approach.
In pre-experiment II with metabolic activation, turbidity of the test item was visible at the two highest test item concentrations (0.25 mg/mL and 0.13 mg/mL). At the next lower test item concentration (0.06 mg/mL) extreme cytotoxicity was observed. Only the three lowest test item concentrations (0.03 mg/mL, 0.02 mg/mL and 0.01 mg/mL) were suitable for scor-ing of micronuclei. At those three concentrations a moderate, very low and no cytotoxic effect was observed. For that reason, this pre-experiment II was evaluated as experiment I with metabolic activation.
In this approach the test item concentration 0.02 mg/mL induced a statistically significant increase in the number of binucleated cells containing micronuclei in comparison to the solvent control. In addition, all three values of the evaluated concentrations exceeded the control range of the solvent control. Only a clear dose-response was not detected since the micronucleus frequency at the highest analysable test item concentration (0.03 mg/mL) was lower than the one at the test item concentration 0.02 mg/mL. However, this effect could possibly be due to the relatively high cytotoxic effect at the concentration 0.03 mg/mL (cytostasis: 43.9 %) that may have led to an interference of cytotoxicity and genotoxicity .
Due to the obviously distinctly increased micronucleus frequencies at all three evaluated test item concentrations , the result of experiment I with metabolic activation is considered as “positive”.
In conclusion, under the experimental conditions reported, (di-p-tolylphosphoryl)(mesityl)methanone is able to induce the formation of micronuclei in hu-man lymphocytes in vitro.
The result of the micronucleus test with the test item (di-p-tolylphosphoryl)(mesityl)methanone is considered as “positive” under the conditions of the test.