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Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification
Justification for type of information:
QMRF report has been attached
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Principles of method if other than guideline:
Prediction was done using the OECD QSAR toolbox version 3.4
GLP compliance:
not specified
Specific details on test material used for the study:
- Name of test material (IUPAC name): 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide
- Molecular formula: C18H17ClN4O5
- Molecular weight: 404.808 g/mol
- Smiles notation: O=C(Nc1ccc(OCC)cc1)[C@@H](\N=N\c1c([N+](=O)[O-])cc(cc1)Cl)C(=O)C
- InChl: 1S/C18H17ClN4O5/c1-3-28-14-7-5-13(6-8-14)20-18(25)17(11(2)24)22-21-15-9-4-12(19)10-16(15)23(26)27/h4-10,17H,3H2,1-2H3,(H,20,25)/b22-21+
- Substance type: Organic
- Physical state: Solid
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Test type:
static
Water media type:
freshwater
Total exposure duration:
72 h
Hardness:
24 mg CaCO3/L
Test temperature:
21.2 - 23.3 °C
pH:
8.0 - 8.2
Nominal and measured concentrations:
Estimated data
Reference substance (positive control):
not specified
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.286 mg/L
Nominal / measured:
estimated
Conc. based on:
not specified
Basis for effect:
growth rate
Remarks on result:
other: Other details not known

The prediction was based on dataset comprised from the following descriptors: EC50
Estimation method: Takes average value from the 5 nearest neighbours
Domain  logical expression:Result: In Domain

((((((((((((((((("a" or "b" or "c" or "d" or "e" )  and ("f" and ( not "g") )  )  and ("h" and ( not "i") )  )  and ("j" and ( not "k") )  )  and ("l" and ( not "m") )  )  and ("n" and ( not "o") )  )  and ("p" and ( not "q") )  )  and ("r" and ( not "s") )  )  and ("t" and ( not "u") )  )  and ("v" and ( not "w") )  )  and ("x" and ( not "y") )  )  and ("z" and ( not "aa") )  )  and ("ab" and ( not "ac") )  )  and "ad" )  and "ae" )  and ("af" and ( not "ag") )  )  and ("ah" and "ai" )  )

Domain logical expression index: "a"

Referential boundary: The target chemical should be classified as Radical AND Radical >> Radical mechanism via ROS formation (indirect) AND Radical >> Radical mechanism via ROS formation (indirect) >> Nitroarenes with Other Active Groups AND SN1 AND SN1 >> Nucleophilic attack after diazonium or carbenium ion formation AND SN1 >> Nucleophilic attack after diazonium or carbenium ion formation >> Nitroarenes with Other Active Groups AND SN1 >> Nucleophilic attack after reduction and nitrenium ion formation AND SN1 >> Nucleophilic attack after reduction and nitrenium ion formation >> Nitroarenes with Other Active Groups AND SN2 AND SN2 >> SN2 attack on activated carbon Csp3 or Csp2 AND SN2 >> SN2 attack on activated carbon Csp3 or Csp2 >> Nitroarenes with Other Active Groups by DNA binding by OASIS v.1.4

Domain logical expression index: "b"

Referential boundary: The target chemical should be classified as SN1 AND SN1 >> Nitrenium Ion formation AND SN1 >> Nitrenium Ion formation >> Aromatic azo AND SN1 >> Nitrenium Ion formation >> Aromatic nitro by DNA binding by OECD

Domain logical expression index: "c"

Referential boundary: The target chemical should be classified as Acylation AND Acylation >> Acylation involving an activated (glucuronidated) carboxamide group AND Acylation >> Acylation involving an activated (glucuronidated) carboxamide group >> Carboxylic Acid Amides AND Acylation >> Direct acylation involving a leaving group AND Acylation >> Direct acylation involving a leaving group >> Carboxylic Acid Amides AND Acylation >> Ester aminolysis AND Acylation >> Ester aminolysis >> Amides AND AN2 AND AN2 >> Michael-type addition to quinoid structures  AND AN2 >> Michael-type addition to quinoid structures  >> Carboxylic Acid Amides by Protein binding by OASIS v1.4

Domain logical expression index: "d"

Referential boundary: The target chemical should be classified as Acylation AND Acylation >> Direct Acylation Involving a Leaving group AND Acylation >> Direct Acylation Involving a Leaving group >> Acetates AND SN2 AND SN2 >> SN2 reaction at sp3 carbon atom AND SN2 >> SN2 reaction at sp3 carbon atom >> Alkyl diazo by Protein binding by OECD

Domain logical expression index: "e"

Referential boundary: The target chemical should be classified as Amides by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "f"

Referential boundary: The target chemical should be classified as Non binder, without OH or NH2 group by Estrogen Receptor Binding

Domain logical expression index: "g"

Referential boundary: The target chemical should be classified as Non binder, impaired OH or NH2 group by Estrogen Receptor Binding

Domain logical expression index: "h"

Referential boundary: The target chemical should be classified as Non binder, without OH or NH2 group by Estrogen Receptor Binding

Domain logical expression index: "i"

Referential boundary: The target chemical should be classified as Weak binder, OH group by Estrogen Receptor Binding

Domain logical expression index: "j"

Referential boundary: The target chemical should be classified as Acylation AND Acylation >> Acylation involving an activated (glucuronidated) carboxamide group AND Acylation >> Acylation involving an activated (glucuronidated) carboxamide group >> Carboxylic Acid Amides AND Acylation >> Direct acylation involving a leaving group AND Acylation >> Direct acylation involving a leaving group >> Carboxylic Acid Amides AND Acylation >> Ester aminolysis AND Acylation >> Ester aminolysis >> Amides AND AN2 AND AN2 >> Michael-type addition to quinoid structures  AND AN2 >> Michael-type addition to quinoid structures  >> Carboxylic Acid Amides by Protein binding by OASIS v1.4

Domain logical expression index: "k"

Referential boundary: The target chemical should be classified as Radical reactions >> ROS generation and direct attack of hydroxyl radical to the C8 position of nucleoside base OR Radical reactions >> ROS generation and direct attack of hydroxyl radical to the C8 position of nucleoside base >> Heterocyclic Aromatic Amines OR SE reaction (CYP450-activated heterocyclic amines) OR SE reaction (CYP450-activated heterocyclic amines) >> Direct attack of arylnitrenium cation to the C8 position of nucleoside base  OR SE reaction (CYP450-activated heterocyclic amines) >> Direct attack of arylnitrenium cation to the C8 position of nucleoside base  >> Heterocyclic Aromatic Amines OR SR reaction (peroxidase-activated heterocyclic amines) OR SR reaction (peroxidase-activated heterocyclic amines) >> Direct attack of arylnitrenium radical to the C8 position of nucleoside base OR SR reaction (peroxidase-activated heterocyclic amines) >> Direct attack of arylnitrenium radical to the C8 position of nucleoside base >> Heterocyclic Aromatic Amines by Protein binding by OASIS v1.4

Domain logical expression index: "l"

Referential boundary: The target chemical should be classified as Acylation AND Acylation >> Direct Acylation Involving a Leaving group AND Acylation >> Direct Acylation Involving a Leaving group >> Acetates AND SN2 AND SN2 >> SN2 reaction at sp3 carbon atom AND SN2 >> SN2 reaction at sp3 carbon atom >> Alkyl diazo by Protein binding by OECD

Domain logical expression index: "m"

Referential boundary: The target chemical should be classified as Acylation >> Ring Opening Acylation >> alpha-Lactams by Protein binding by OECD

Domain logical expression index: "n"

Referential boundary: The target chemical should be classified as Amides by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "o"

Referential boundary: The target chemical should be classified as Acid moiety by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "p"

Referential boundary: The target chemical should be classified as Amides by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "q"

Referential boundary: The target chemical should be classified as Alkoxy Silanes by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "r"

Referential boundary: The target chemical should be classified as Amides by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "s"

Referential boundary: The target chemical should be classified as Carbonyl Ureas by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "t"

Referential boundary: The target chemical should be classified as Amides by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "u"

Referential boundary: The target chemical should be classified as Hydrazines by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "v"

Referential boundary: The target chemical should be classified as Amides by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "w"

Referential boundary: The target chemical should be classified as Phenol Amines by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "x"

Referential boundary: The target chemical should be classified as Amides by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "y"

Referential boundary: The target chemical should be classified as Substituted Ureas by Aquatic toxicity classification by ECOSAR

Domain logical expression index: "z"

Referential boundary: The target chemical should be classified as Halogens AND Non-Metals by Groups of elements

Domain logical expression index: "aa"

Referential boundary: The target chemical should be classified as Metalloids by Groups of elements

Domain logical expression index: "ab"

Referential boundary: The target chemical should be classified as Alkoxy AND Aryl AND Aryl halide AND Azo AND Ether AND Ketone AND Nitrobenzene AND Organic amide and thioamide by Organic Functional groups

Domain logical expression index: "ac"

Referential boundary: The target chemical should be classified as Alcohol by Organic Functional groups

Domain logical expression index: "ad"

Similarity boundary:Target: CCOc1ccc(NC(=O)C(C(C)=O)N=Nc2ccc(Cl)cc2N(=O)=O)cc1
Threshold=20%,
Dice(Atom centered fragments)
Atom type; Count H attached; Hybridization

Domain logical expression index: "ae"

Similarity boundary:Target: CCOc1ccc(NC(=O)C(C(C)=O)N=Nc2ccc(Cl)cc2N(=O)=O)cc1
Threshold=40%,
Dice(Atom centered fragments)
Atom type; Count H attached; Hybridization

Domain logical expression index: "af"

Referential boundary: The target chemical should be classified as (!Undefined)Group All Lipid Solubility < 0.01 g/kg AND (!Undefined)Group CNHal Lipid Solubility < 4 g/kg AND (!Undefined)Group CNHal Lipid Solubility < 400 g/kg AND Group All Melting Point > 200 C AND Group CNHal Aqueous Solubility < 0.001 g/L AND Group CNHal Aqueous Solubility < 0.1 g/L AND Group CNHal log Kow > 3.8 AND Group CNHal Molecular Weight > 370 g/mol AND Group CNHal Molecular Weight > 380 g/mol by Skin irritation/corrosion Exclusion rules by BfR

Domain logical expression index: "ag"

Referential boundary: The target chemical should be classified as Group All log Kow > 9 by Skin irritation/corrosion Exclusion rules by BfR

Domain logical expression index: "ah"

Parametric boundary:The target chemical should have a value of log Kow which is >= 0.0716

Domain logical expression index: "ai"

Parametric boundary:The target chemical should have a value of log Kow which is <= 8.45

Validity criteria fulfilled:
not specified
Conclusions:
Based on the growth rate inhibition, the EC50 value was estimated to be 0.28 mg/l when 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N- (4-ethoxyphenyl)-3-oxobutanamide exposed to Pseudokirchneriella subcapitata for 72 hrs.
Executive summary:

Based on the prediction done using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the six closest read across substances, toxicity on Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum) was predicted for 2-[(E)-2-(4-chloro-2-nitrophenyl) diazen-1-yl]-N- (4-ethoxyphenyl)-3-oxobutanamide (52320-66-8). Based on the growth rate inhibition, the EC50 value was estimated to be 0.28 mg/l when 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N- (4-ethoxyphenyl)-3-oxobutanamide exposed to Pseudokirchneriella subcapitata for 72 hrs. Based on this value it can be concluded that the substance 2 -[(E)-2-(4-chloro-2-nitrophenyl) diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (52320-66-8) is considered to be toxic to aquatic environment and classified as aquatic acute 1 as well as chronic 1 category as per the criteria mentioned in CLP regulation.   

Description of key information

Based on the prediction done using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the six closest read across substances, toxicity on Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum) was predicted for 2-[(E)-2-(4-chloro-2-nitrophenyl) diazen-1-yl]-N- (4-ethoxyphenyl)-3-oxobutanamide (52320-66-8). Based on the growth rate inhibition, the EC50 value was estimated to be 0.28 mg/l when 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N- (4-ethoxyphenyl)-3-oxobutanamide exposed to Pseudokirchneriella subcapitata for 72 hrs. Based on this value it can be concluded that the substance 2 -[(E)-2-(4-chloro-2-nitrophenyl) diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (52320-66-8) is considered to be toxic to aquatic environment and classified as aquatic acute 1 as well as chronic 1 category as per the criteria mentioned in CLP regulation.   

Key value for chemical safety assessment

EC50 for freshwater algae:
0.28 mg/L

Additional information

Various predicted data for the target compound 2-[(E)-2-(4-chloro-2-nitrophenyl) diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (52320-66-8) and experimental studies for supporting weight of evidence studies for its closest read across substance with log Kow as the primary descriptor and on the basis of structural and functional similarity were reviewed for the toxicity on the algal end point which are summarized as below: 

In a prediction done by SSS (2017), based on the prediction done using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the six closest read across substances, toxicity on Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum) was predicted for 2-[(E)-2-(4-chloro-2- nitrophenyl) diazen-1-yl]-N- (4-ethoxyphenyl)-3-oxobutanamide (52320-66-8). Based on the growth rate inhibition, the EC50 value was estimated to be 0.28 mg/l when 2-[(E)-2-(4-chloro- 2-nitrophenyl)diazen-1-yl]-N- (4-ethoxyphenyl)-3-oxobutanamide exposed to Pseudokirchneriella subcapitata for 72 hrs. Based on this value it can be concluded that the substance 2 -[(E)-2-(4-chloro-2-nitrophenyl) diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (52320-66-8) is considered to be toxic to aquatic environment and classified as aquatic acute 1 as well as chronic 1 category as per the criteria mentioned in CLP regulation.  

 

First predicted study was supported by the structurally and functionally similar read across chemical (103-90-2) from Environmental Toxicology and Chemistry 2006. Aim of the study was to assess the effect of chemical 4' Hydroxyacetanilidon (Acetaminophen) on the growth of freshwater alga Selenastrum capricornutum for the exposure period of 72 hrs. Testing was conducted according to the published Environment Canada biological test method. Test chemical was analytically monitored by HPLC method and also separation done by reverse-phase column using binary gradient elution at a constant temperature of 25°C. The neutral drugs were analyzed individually by full-scan MS in positive-ion mode, and quantitative analyses were performed using selective-ion monitoring mode. Algae exposed for chemical for 72 hrs and effect was observed based on the inhibition of algal cell inhibition. Based on the inhibition of the number of living algal cells and biomass of Pseudokirchneriella subcapitala (S. capricornutum) the IC25 was >0.032 mg/l. Thus based on the IC25, it can be concluded that the chemical was toxic and can be consider to be classified as aquatic acute 1 as well as chronic 1 category as per the CLP classification criteria.

 

Similarly in a supporting weight of evidence study for read across chemical (50-65-7) from ECOTOX database 2018 study was conducted. Study was conducted to determine the short term toxicity of 5-Chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide to algae Scenedesmus subspicatus (Green Algae). Test was conducted under the static system for the total exposure period of 48 hrs. Based on the biomass inhibition of green algae (Scenedesmus subspicatus) due to the chemical 5-Chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide exposure for 48 hrs, the EC50 was 0.96 mg/l. Thus based on the EC50 chemical was consider as toxic and can be consider to be classified as aquatic acute1/chronic 1 category as per the CLP classification criteria.

 

On the basis of above results for target chemical 2-[(E)-2-(4-chloro-2-nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (52320-66-8) (from OECD QSAR toolbox version 3.4) and for its read across substance from Environmental Toxicology and Chemistry 2006 and ECOTOX database it can be concluded that the test substance 2-[(E)-2-(4-chloro-2- nitrophenyl)diazen-1-yl]-N-(4-ethoxyphenyl)-3-oxobutanamide (52320-66-8) is toxic and can be consider to be classified as aquatic acute1/chronic 1 category as per the CLP classification criteria.