Sodium 3-[(1,5-dihydroxy-2-naphthyl)azo]-4-hydroxybenzenesulphonate

Endpoint summary

Description of key information

Toxicokinetic assessment

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Introduction

Toxicokinetic parameters such as uptake, distribution, metabolism and excretion form the essential toxicological profile of a substance. An approximate indication of the toxicokinetic pattern can be gained from the physico-chemical properties taking into account the molecular weight, the number of atoms (hydrogen bond donors and acceptors), the solubility in solvents, log K_OW, etc. and the results of basic toxicity testing of the test article. The assessment of the toxicokinetic properties of Mordant Black 9 given below is based on the results obtained for, the following toxicological endpoints:

 

·        Acute oral toxicity in rats

·        In vivo skin irritation in rabbits

·        In vivo eye irritation in rabbits

·        Bacterial reverse mutation test

Allstudieswere carried out according to the principles of Good Laboratory Practice and met the requirements of the OECD and EU-Guideline for the Testing of Chemicals.

Physico-chemical properties

Name:                                       Mordant Black 9

CAS number:                          2052-25-7,85750-02-3

CAS name:                              Benzenesulfonic acid, 3-((1,5-dihydroxy-2-naphthalenyl)azo)-4-hydroxy-, sodium salt

Empirical formula:               C₁₆H₁₁N₂NaO₆S

Molecular weight:                 382.3g/mol                                   (<500 daltons = good absorption)

Atom count (natoms):       26                                                (<70 = good bioavailability)

H-bond acceptor (nON):  8                                                (<10 = good bioavailability)

H-bond donor (nOHNH):   3            (<5 = good bioavailability)

 

CAS number:                         25747-07-3

CAS name:                             Benzenesulfonic acid, 3-((1,5-dihydroxy-2-naphthalenyl)azo)-4-hydroxy-

Empirical formula:               C₁₆H₁₂N₂O₆S

Molecular weight:                 360.3 g/mol                                   (<500 daltons = good absorption)

Atom count (natoms):       25                                                (<70 = good bioavailability)

H-bond acceptor (nON):  8                                                (<10 = good bioavailability)

H-bond donor (nOHNH):     4           (<5 = good bioavailability)

 

Physical state:                       solid, black odourless powder

Water solubility:                    48 g/L                                             (= soluble in water)

Partition coefficient:             log Kow= -1.4                              (<-0.4 or >5.6 =bad absorption)

Surface tension:                     48.2 mN/m                                     (<60 = surface active)

Melting point:                        > 400°C                                          (not volatile = not inhalable)

Vapor pressure:                     3.31E-8 hPa                                   (not volatile = not inhalable)

 

Toxicological Profile

After single oral administration of Mordant Black 9 at a dose level of 5000 mg/kg body weight to male and female rats no deaths or clinical signs other than unspecific signs of toxicity occurred. The median lethal dose (LD₅₀) of Mordant Black 9 after oral administration to rats is greater than 5000 mg/kg body weight. Testing for skin irritating properties of Mordant Black 9 in rabbits did not lead to any adverse effects.

Mordant Black 9 was tested for bacterial mutagenicity in the presence and absence of rat and hamster S9-mix. The test compound did not cause a significant increase in the number of revertant colonies with any of the tester strains either in the absence or in the presence of S9-mix in either of these tests.

Evaluation and Assessment

Based on all available data, Mordant Black 9 does not exhibit a conspicuous toxicokinetic behavior.

Mordant Black 9 is a dark blue powdered solid at room temperature conditions. The degree of purity of the substance is 40 - 80%. The melting point of the substance is >400°C therefore a significant inhalation exposure to vapours is not expected. In view of the good water solubility and the low n-octanol/water partition coefficient (log Kow = – 1.4 at 20°C), systemic bioavailability after dermal exposure is not anticipated. This in accordance with the dermal irritation test.

Physico-chemical data such as molecular weight, atom count, number of H-bond donor and acceptors give evidence of a good oral systemic bioavailability. However, according to the data of the acute oral toxicity testing, Mordant Black 9 has a very low acute toxicity potential.

According to its molecular weight, Mordant Black 9 is most likely predominantly eliminated via intestine, as substances with a molecular weight above 300 g/mol are preferentially excreted via the feces in rats. However, it is most likely that the test compound is at least partly eliminated via kidneys/urine, too.

According to its low log Kow and the bioaccumulation modeling a significant bioaccumulation potential of Mordant Black 9 can be excluded.

Additionally, Mordant Black 9 was also not genotoxic in an in-vitro cell mutagenicity test. Therefore, a metabolisation towards genotoxic structures can most probably be excluded.

Summary

The results of basic toxicity testing give no reason to anticipate unusual characteristics with regards to the toxicokinetics of Mordant Black 9. The data indicate that there is little or no dermal absorption. No signs of a significant systemic toxicity associated with absorption potential have been observed. Bioaccumulation of Mordant Black 9 can most probably be excluded due to the available data. Based on the results of genotoxicity assays, a metabolisation towards genotoxic metabolites can also be excluded.

On the basis of the results, it is anticipated that the substance does not undergo significant metabolic activity; rather it is metabolized for excretion with little subsequent toxicity. The substance is therefore not considered to be of concern for ADME related effects.