tryptophan

American  

[trip-tuh-fan] / ˈtrɪp təˌfæn /

Also tryptophane

noun

Biochemistry.

1. an essential amino acid, (C 8 H 6 N)CH 2 CH(NH2 )COOH, colorless, crystalline, and aromatic, released from proteins by tryptic digestion and a precursor of serotonin. Trp; W

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tryptophan British  

/ ˈtrɪptəˌfæn /

noun

1. an essential amino acid; a component of proteins necessary for growth

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tryptophan Scientific  

/ trĭp′tə-făn′ /

1. An essential amino acid. Chemical formula: C ₁₁ H ₁₂ N ₂ O ₂ .

2. See more at amino acid

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Etymology

Origin of tryptophan

1900–05; trypto- (irregular combining form representing Greek trīptós “rubbed”) + -phan(e) ( def. )

Example Sentences

As a result, tryptophan is redirected toward the kynurenic pathway, which produces neurotoxic compounds, while the production of protective neurotransmitters such as serotonin and melatonin declines.

From Science Daily • Jan. 15, 2026

Partly because I was exhausted from the tryptophan I had ingested with my turkey the day before and could not get out of bed.

From The Wall Street Journal • Nov. 28, 2025

No—they’re football tryptophan, a snoozy bore to watch.

From The Wall Street Journal • Nov. 24, 2025

Again, based on pathogen levels and inflammation, when these three metabolites alone were fed to the mice, they had the same protective effect as giving the mice a full tryptophan diet.

From Science Daily • Mar. 13, 2024

Maize lacks digestible niacin, the amino acids lysine and tryptophan, necessary to make proteins and diets with too much maize can lead to protein deficiency and pellagra, a disease caused by lack of niacin.

From "1491" by Charles C. Mann