DL-Tryptophan-d5 is a deuterated compound of DL-Tryptophan. DL-Tryptophan has a CAS number of 54-12-6. Tryptophan containing dipeptides are interesting ingredients for functional foods as a natural prevention for hypertension with reduced side effects due to its selective inhibition of the C-domain. Low thalamic Tryptophan uptake appears to be a strong, independent predictor of long survival in patients with previous glioma treatment.