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L-Tryptophan is an essential amino acid and a precursor to both serotonin and melatonin. Serotonin is a neurotransmitter playing a role in regulating appetite, sleep, mood, and pain. Melatonin is a hormone modulating sleep and wakefulness.
Protein supplement in health care products.

L-Amino Acids
Catalog number
CAS number
Molecular Formula
Molecular Weight
(2S)-2-amino-3-(1H-indol-3-yl)propanoic acid
H-Trp-OH; L-Tryptophane; L-Tryptohan
White to Slightly Yellowish Crystals or Crystalline Powder
Melting Point
280-285 °C (dec.)
Boiling Point
447.9 ℃ / 760 mmHg
Store at RT
water, 2848 mg/L @ 25 °C (est)
Ingredient of health care products.
InChI Key
Canonical SMILES
1.Assessment of tryptophan metabolism and signs of depression in individuals with carbohydrate malabsorption.
Enko D;Wagner H;Kriegshäuser G;Brandmayr W;Halwachs-Baumann G;Schnedl WJ;Zelzer S;Mangge H;Meinitzer A Psychiatry Res. 2018 Apr;262:595-599. doi: 10.1016/j.psychres.2017.09.049. Epub 2017 Sep 22.
This prospective cross-sectional study aimed to investigate the potential association between primary-adult lactose malabsorption, fructose malabsorption, tryptophan (TRP) metabolism and the presence of depressive signs. Overall 251 patients, who were referred for lactase gene C/T;-13910; polymorphism genotyping and fructose hydrogen/methane breath testing, were included. All participants filled out the Beck Depression Inventory (BDI II). Serum concentrations of tryptophan (TRP), kynurenine (KYN), kynuric acid (KYNA), and TRP competing amino acids (leucine, isoleucine, valine, phenylalanine, tyrosine) were measured by high-pressure liquid-chromatography. Logistic regression analysis was performed with lactose malabsorption, fructose malabsorption and all potential biomarkers of TRP metabolism to assess the effect on signs of depression, defined as a BDI II score > 13. Primary-adult lactose malabsorption and fructose malabsorption was detected in 65 (25.90%) and 65 (25.90%) patients, respectively. Fructose malabsorption was significantly associated with BDI II score, whereas no such relationship was found for lactose malabsorption. Serum levels of TRP and TRP metabolites were no predictors of depression.
2.Short-term supplementation of isocaloric meals with L-tryptophan affects pig growth.
Liu HN;Hu CA;Bai MM;Liu G;Tossou MCB;Xu K;Li FN;Liao P;Kong XF;Wu X;Yin YL Amino Acids. 2017 Dec;49(12):2009-2014. doi: 10.1007/s00726-017-2440-3. Epub 2017 May 24.
L-Tryptophan (Trp) and some of its metabolites regulate the circadian rhythm in mammals. We aimed to investigate the effects of short-term supplementation of Trp in isocaloric meals on growth performance using the parameters of multiple blood biomarkers and free amino acids in growing pigs. A total of 32 Landrace × Yorkshire barrows with a mean body weight of 8.64 (±1.13) kg were randomly assigned to four groups and then fed with various concentrations of Trp diets daily. Our results showed that sequential supplementation of different concentrations of Trp in isocaloric meals decreased the feed:gain (F:G) ratio (P = 0.079) and plasma urea and albumin (P = 0.019), whereas the level of total protein did not. Among the essential and conditionally essential amino acids, the concentrations of histidine, isoleucine, proline, threonine, arginine, and valine in the plasma decreased (P < 0.05), whereas the concentrations of Trp, glycine, serine, and methionine increased (P < 0.01). In addition, concentrations of branched chain amino acids also significantly decreased (P = 0.004), while the rate of conversion of Trp to branched chain amino acids increased (P < 0.001). Taken together, we show that administration of a high concentration of Trp in breakfast with decreasing concentrations of Trp in lunch and dinner positively affected feed utilization and improved feed efficiency, at least in part, through the optimization of amino acid interconversions and nitrogen utilization.
3.Effects of tryptophan-containing peptides on angiotensin-converting enzyme activity and vessel tone ex vivo and in vivo.
Khedr S;Deussen A;Kopaliani I;Zatschler B;Martin M Eur J Nutr. 2018 Apr;57(3):907-915. doi: 10.1007/s00394-016-1374-y. Epub 2017 Jan 19.
PURPOSE: ;Over-activation of the renin-angiotensin axis and worsening of vascular function are critical contributors to the development of hypertension. Therefore, inhibition of angiotensin-converting enzyme (ACE), a key factor of the renin-angiotensin axis, is a first line treatment of hypertension. Besides pharmaceutical ACE inhibitors, some natural peptides have been shown to exert ACE-inhibiting properties with antihypertensive effects and potentially beneficial effects on vascular function. In this study, the ACE-inhibiting potential and effects on vascular function of tryptophan-containing peptides were evaluated.;METHODS: ;The ACE inhibitory action and stability of tryptophan-containing peptides was tested in endothelial cells-a major source of whole body ACE activity. Furthermore, the efficacy of peptides on vascular ACE activity, as well as vessel tone was assessed both ex vivo and in vivo.;RESULTS: ;In human umbilical vein endothelial cells (HUVEC), isoleucine-tryptophan (IW) had the highest ACE inhibitory efficacy, followed by glutamic acid-tryptophan (EW) and tryptophan-leucine (WL). Whereas none of the peptides affected basal vessel tone (rat aorta), angiotensin I-induced vasoconstriction was blocked.

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