Registration Dossier
Registration Dossier
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EC number: 200-522-0 | CAS number: 61-90-5
Short-term toxicity to fish
Administrative data
Link to relevant study record(s)
Description of key information
No test results for L-leucine are available. However, based on test results available for read-across substance L-valine it can be concluded that acute toxicity to fish is not expected to occur upon exposure to up to 1000 mg/L of L-leucine.
Key value for chemical safety assessment
Additional information
No test results for L-leucine are available. However, read-across to the test results available for structural analogue L-valine is deemed justified based on a comparison of the main factors driving environmental toxicity: pH, water solubility, log Kow and chemical reactivity (functional groups).
- both are essential amino acids that are in the zwitterion state at physiological pH
- the chemical structure differs only in that L-leucine has one extra methylene group in the aliphatic side chain
- the pKa values of the α-COOH group is very similar: 2.36 for LEU, 2.32 for VAL
- the pKa values of the α-NH2 group is very similar: 9.60 for LEU, 9.62 for VAL
- the substances both have a high water solubility: 23 g/L for LEU, 58 g/L for VAL
- the substance both have a low log Kow value: -1.59 for LEU (calculated by EpiWin QSAR), -2.08 for VAL (calculated by EpiWin QSAR)
As the chemical structure and reactivity, and the water solubility, log Kow and pKa values of L-leucine and L-valine are almost identical, it can be concluded that read-across for aquatic toxicity information between those 2 substances is acceptable.
The tests available for L-valine are carried out according to OECD guidelines and reveal no fish mortality at the highest tested concentrations (1000 mg/L for the key study, 10000 mg/L for the supporting study. As a consequence, acute toxicity to fish is not expected to occur upon exposure to the L-leucine up to a concentration of 1000 mg/L.
This is further confirmed by the result of the QSAR (EcoSAR, EpiSuite) that predicted an 96h-LC50 of > 33000 mg/L for L-leucine.
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