Registration Dossier
Registration Dossier
Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.
The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.
Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 200-795-6 | CAS number: 73-22-3
Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
Key value for chemical safety assessment
- Bioaccumulation potential:
- no bioaccumulation potential
- Absorption rate - oral (%):
- 100
- Absorption rate - dermal (%):
- 10
- Absorption rate - inhalation (%):
- 100
Additional information
L-tryptophan is an essential amino acid, which cannot be synthesized in the human body and must be supplied by the diet. In humans, tryptophan has relatively low tissue storage and the overall tryptophan concentration in the body is the lowest among all amino acids. Tryptophan plays a significant role for a multitude of metabolic functions and processes (e.g. syntheses of protein, serotonin, melatonin and NAD/NADP). Tryptophan is the sole precursor of serotonin and is distributed throughout the human body in the circulatory system (about 75-85% of tryptophan is bound to albumin). After uptake and metabolism, tryptophan is mainly excreted via urine and as metabolites kynurenine, kynurenic acid, 3-hydroxykynurenine, 3-hydroxyanthranilic acid, and xanthurenic acid can be determined.
For risk assessment purposes oral absorption of L-tryptophan is set at 100%. This assumption is based upon the physiological mechanisms of absorption. L-tryptophan is of low volatility due to a extremely low vapour pressure. From this and from the particle size it is not expected that L-tryptophan reaches the nasopharyncheal region or subsequently the tracheobronchial or pulmonary region in significant amounts. However, being a very hydrophilic substance with a low molecular mass any L-tryptophan reaching the lungs might be absorbed through aqueous pores. For risk assessment purposes, although it is unlikely that L-tryptophan will be available to a high extent after inhalation via the lungs due to the low vapour pressure, the inhalation absorption of L-tryptophan is set at 100%. L-tryptophan with high water solubility (11.4 g/L) and the log P value below 0 (-1.06) is expected to be too hydrophilic to cross the lipid rich environment of the stratum corneum. Therefore, for risk assessment purposes dermal absorption of L-tryptophan is set at 10%.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
