L-serine

Endpoint summary

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin irritation

There is no skin irritation study for L-serine available. However, there is an in vivo OECD 404 GLP-guideline study available for L-threonine. L-Serine and L-threonine belong to the group of polar amino acids as their side chains are polar but not charged. Their chemical structure is very similar with both having the same set of functional groups. The only difference between the two molecules is that L-threonine contains one additional methyl group in the amino acid side chain. Both substances have a low molecular weight, nearly identical logKow values (~-3) and also very similar pKa values. In addition to similar physico-chemical properties also toxicological and ecotoxicological/fate data indicate a very low toxicity (if any) of both substances for the environment (toxicity for aquatic organisms) as well as a very low toxicity (if any) for human health (toxicity to experimental animals). The absence of significant toxicity is not surprising as both substances are ubiquitous occurring substances (also in body fluids of animals and humans) which serve as building blocks for protein synthesis in all animals (including humans). Due to the very similar chemical structure resulting in very similar physico-chemical properties and a very low (eco)toxicity profile of both substances it is justified to fulfil the data requirement for L-serine with regard to skin irritating properties by a read-across approach from available data for L-threonine.

In the available study l-threonine has no skin irritating properties. Further, according to the exclusion rules of the Bundesanstalt für Risikoforschung (BfR rules) it is suggested that neither L-threonine nor L-serine are skin irritants due to their physico-chemical properties.

This finally leads to the conclusion that L-serine is not a skin irritant.

Eye irritation

Also for the endpoint eye irritation no study for L-serine is available. Again an in vivo OECD 405 GLP-guideline study is available for L-threonine. As explained above it is justified to read-across also for eye irritation properties. In the available study L-threonine has no eye irritating properties at all. Further, in an in vivo study similar to the OECD 408 repeated dose toxicity study (the highest dose was 3000 mg/kg bw - oral gavage) no irritation of mucous membranes was reported.

 

This finally leads to the conclusion that L-serine is not an eye irritant.