Registration Dossier

Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

Administrative data

Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
MODEL DESCRIPTION
The EAWAG-BBD Pathway Prediction System (also known as Minnesota Pathway Prediction System) is a web-based tool (http://eawag-bbd.ethz.ch/predict/) and can be used free of charge.

1.1.1 Purpose:
The model predicts plausible pathways for microbial degradation of chemical compounds. Predictions use biotransformation rules, based on reactions found in the EAWAG-BBD database or in the scientific literature. A list of all rules is available and comprises currently 332 different pathways.
PPS predictions are most accurate for compounds that are:
• similar to compounds whose biodegradation pathways are reported in the scientific literature;
• in environments exposed to air, in moist soil or water, at moderate temperatures and pH, with no competing chemicals or toxins; and
• the sole source of energy, carbon, nitrogen, or other essential element for the microbes in these environments, rather than present in trace amounts.
1.1.2 Scope:
There are a number of chemical classes that should not be investigated using the current version of the Pathway Prediction System. Important classes of chemicals whose biodegradation should not be predicted are listed below.
This list is based on a similar list developed for the PBT System by the Environmental Science Center under contract to the Office of Pollution Prevention and Toxics, U.S. Environmental Protection Agency.
• Readily Degraded and Selected Other Compounds
• Inorganic Chemicals
• High Molecular Weight Compounds
• Chemicals with Unknown or Variable Composition
• Mixtures
• Highly Fluorinated Compounds

1.2 VALIDITY OF THE MODEL:
The model contains currently a high number (332) of different pathways described in the scientific literature. For Solvent Green 28 the model revealed the following theoretical pathways:
• 1-Hydroxy-2-unsubstituted aromatic -> 1,2-Dihydroxyaromatic (bt0014)
• Anthrone derivative -> 2-[(2-Hydroxyphenyl)methyl]benzoate derivative (bt0418)
• 1,2-Dihydroxybenzenoid w fused aliphatic ring -> 2-Oxo-3-butenoate aliphatic ring (bt0342)

As a result, the high number of pathways included in the model gave relevant pathways fitting to the substance. Furthermore, the substance is not excluded from the classes of chemicals whose biodegradation should not be predicted

2. MODEL INPUT PARAMETERS:
The only input parameter needed for the model is the chemical structure which is described by the smiles code.
• CC(C)(C)c1ccc(Nc2ccc(Nc3ccc(cc3)C(C)(C)C)c4C(=O)c5c(O)ccc(O)c5C(=O)c24)cc1

Data source

Reference
Reference Type:
other company data
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
The EAWAG-BBD Pathway Prediction System (also known as Minnesota Pathway Prediction System) is a web-based tool (http://eawag-bbd.ethz.ch/predict/) which predicts plausible pathways for microbial degradation of chemical compounds. Predictions use biotransformation rules, based on reactions found in the EAWAG-BBD database or in the scientific literature. A list of all rules is available and comprises currently 332 different pathways.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid
Details on test material:
- SMILES: CC(C)(C)c1ccc(cc1)Nc5ccc(Nc2ccc(cc2)C(C)(C)C)c4C(=O)c3c(O)ccc(O)c3C(=O)c45
- Molecular weight: 534.64 g/mole

Results and discussion

% Degradation
Remarks on result:
other: Neutral and likely routes for degradation were found by the model, but no very likely routes.
Transformation products:
not measured
Details on transformation products:
Details of possible transformation products are given in the full report attached.

Any other information on results incl. tables

The primary metabolism follows two possible routes which are the oxidative cleavage of the amine group and the cleavage of the anthrone ring system. The second route was found to occur “neutral”. Neutral means that this pathway is theoretically possible. EAWAG defines reaction to be neutral as follows: Possible reaction (neutral). This applies to reactions that are common but not certain to occur in every system. For example, hydrocarbon oxygenation reactions are quite possible, but may or may not be likely to occur depending on what the substrate is. These must be looked at individually. Some may be likely, some may be possible and some may be unlikely based on current knowledge.

In case of Solvent Green 28, the neutral pathway has to be understood that degradation is more unlikely than likely. This means that the first step is expected to occur slowly and subsequent secondary or tertiary pathways would not lead to relevant biodegradation and mineralization.

The other primary route of biodegradation is the oxidative cleavage of the amino function which is described to occur “likely”.  EAWAG defines reaction to be neutral as follows: Likely reaction. This is to be used when almost all bacteria can catalyze a given reaction with a functional group present in a molecule. For example, if the substrate has an ester linkage, it is often hydrolyzed by very common esterases, found both extracellularly and intracellularly. So giving an ester hydrolysis rule a score of 2 would give it a high priority but after an acid chloride hydrolysis reaction. You should also use 2 for a reaction that is significantly likely to occur once a certain intermediate has been generated. For example, aromatic ring cis-dihydrodiols are likely to be dehydrogenated to form catechols. Most organisms that make cis-dihydrodiols will also catalyze their dehydrogenation, thus the latter reaction is likely due to the linkage.

Applicant's summary and conclusion

Validity criteria fulfilled:
not applicable
Conclusions:
The outcome of the pathway prediction system is that biodegradation of Solvent Green 28 is possible via the route “oxidative cleavage of the amino function”. Other routes do not occur or are rather slowly.
Executive summary:

Solvent Green 28 (Macrolex Grün G, CAS-No. 4851-50-7) was found to be not readily biodegradable in a test according to OECD 301 series. The EAWAG-BBD Pathway Prediction System is a tool which allows prediction of microbial degradation in order to assess the behavior of the substance in the environment. The model predicts the following degradation steps:

Primary degradation:              Dihydroxylation of the aromatic ring system       “likely”

Cleavage of the Anthrone ring system              “neutral”

Secondary degradation:       Oxidative cleavage of the dihydroxylated ring       “likely”                                   

Cleavage of the Anthrone ring system              “neutral”

The model predicts that common microbial metabolisation routes can be applied for Solvent Green 28. Beside possible pathways and structure of metabolites, the model predicts a qualitative description of the routes as “very likely”, “likely” and “neutral” with neutral or likely to be the likelihood to be expected in this case. Based on the prediction, the classification as “neutral” means that the primary degradation steps are expected to be possible but that they are not certain to occur in every system. “Likely” reaction is used when almost all bacteria can catalyse a given reaction with a functional group present in a molecule. The overall outcome of the prediction is that there are several neutral pathways but one likely pathway which might possibly cause biotic degradation.