Tryptophan (C₁₁H₁₂N₂O₂) — Properties, Uses & Safety

Overview

Tryptophan (C11H12N2O2) is an essential amino acid with a molar mass of 204.23 g/mol, meaning the human body cannot synthesize it and must obtain it from dietary sources. It appears as a white crystalline solid and has a distinctive molecular structure featuring an indole ring system — a bicyclic aromatic group consisting of a benzene ring fused to a pyrrole ring — attached to the standard amino acid backbone (amino group, carboxylic acid group, and alpha-carbon). This indole side chain makes tryptophan the largest and most structurally complex of the 20 standard amino acids and gives it unique UV-absorption properties (absorption maximum near 280 nm), which is why protein concentration can be estimated by UV spectroscopy. Tryptophan is famously associated with the drowsiness people feel after Thanksgiving turkey, though in reality, turkey contains no more tryptophan than other meats — the sleepiness is more likely due to overeating and carbohydrate-rich side dishes. Biochemically, tryptophan is the precursor to serotonin (a neurotransmitter that regulates mood, sleep, and appetite) and melatonin (the hormone that controls the sleep-wake cycle). It is also converted to niacin (vitamin B3) in the body. Dietary sources include turkey, chicken, cheese, nuts, seeds, tofu, and eggs. Tryptophan has no significant GHS hazard classifications. For chemistry students, tryptophan illustrates amino acid structure and classification, aromatic heterocyclic chemistry (the indole ring), chirality (only L-tryptophan is biologically active), UV spectroscopy and chromophores, peptide bond formation, and the biochemical pathways connecting amino acids to neurotransmitters and hormones. It demonstrates how a single amino acid can have far-reaching effects on brain chemistry and human behavior, bridging organic chemistry with neuroscience and nutrition.

IUPAC Name

(S)-2-amino-3-(1H-indol-3-yl)propanoic acid

CAS Number

73-22-3

PubChem CID

6305

Molecular Formula

C₁₁H₁₂N₂O₂

Molar Mass

204.228 g/mol

State at STP

solid

Appearance

White crystalline solid