Tryptophan

Tryptophan is an essential aromatic amino acid that humans must obtain from the diet because it cannot be synthesized de novo. It serves primarily as a precursor for the neurotransmitter serotonin (5‑hydroxytryptamine) and the hormone melatonin, thereby influencing mood, sleep, and a variety of neuro‑endocrine functions.

• Chemical Identity: L‑Tryptophan (C₁₁H₁₂N₂O₂) is a non‑polar, aromatic α‑amino acid.
• IUPAC Name: (2S)-2-amino-3-(indol-3-yl)propanoic acid.
• Structure: Its structure features a central α‑carbon bearing an amino group, a carboxyl group, and a side‑chain consisting of an indole ring (a fused benzene‑pyrrole system) attached at the 3‑position.
• Chirality: The molecule is chiral; the naturally occurring L‑enantiomer is biologically active.
• Molecular Weight: 204.23 g/mol; pKa values: ~2.4 (carboxyl) and ~9.4 (amino).
• Solubility and Stability: It is moderately water‑soluble (≈10 g/L at 25 °C) and exhibits limited stability in aqueous solution at pH > 7, where it can undergo oxidation to kynurenine derivatives.
• BBB Permeability: The indole moiety confers aromaticity and contributes to its ability to cross the BBB via LAT1.

• Dietary Sources: Dietary tryptophan is abundant in high‑protein foods: turkey, chicken, eggs, dairy, fish, and legumes (e.g., soy, lentils).
• Supplement Production: Commercial supplements are produced by enzymatic hydrolysis of protein sources (e.g., soy or wheat) followed by chromatographic purification to yield ≥99 % L‑tryptophan.
• Fermentation: Fermentation using Corynebacterium glutamicum or E. coli engineered for high tryptophan production is increasingly common, providing a non‑allergenic, GMO‑controlled source.
• Quality Considerations: Quality considerations include verification of ≥99 % purity, absence of the 1990s‑era contaminants (e.g., 1‑methyl‑4‑phenyl‑pyridyl), and compliance with USP/NF or European Pharmacopeia standards.
• Third-Party Testing: Third‑party testing (e.g., USP, NSF) is recommended to ensure batch‑to‑batch consistency and to avoid heavy‑metal or microbial contamination.