BACKGROUND: Tryptophan is an amino acid, which is responsible for the production of serotonin in the body. Lower levels of tryptophan may play a role in pediatric disorders. In this work the urinary level of tryptophan in autistic and healthy children was compared. MATERIAL/METHODS: The samples of urine were taken from 33 autistic children (10 on a restricted diet of gluten and casein free and 23 no diet) and 21 healthy children. The level of tryptophan was determined by gas chromatography/mass spectrometry (GC/MS). In this method tryptophan was derivatized and extracted simultaneously. The method was validated. RESULTS: Significantly lower relative urinary levels of tryptophan were obtained for both autistic children with a restricted diet 1.98+/-1.17 microg/mL (mean +/-SD) and autistic children without a diet 7.44+/-1.33 microg/mL (mean +/-SD) compared to healthy children 14.24+/-2.01 microg/mL (mean +/-SD). The method has a limit of quantification (LOQ) of 0.15 microg/mL and a lower limit of detection (LOD) of 0.04 microg/mL for tryptophan in urine. CONCLUSIONS: This method is precise and sensitive for the detection of low concentrations of tryptophan and can be applicable to monitoring its level in human urine. Children with autism have a higher deficiency of tryptophan than the control group of healthy children. Lower levels of tryptophan may lead to the worsening of autistic symptoms such as mild depression and increased irritability.
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