L-tryptophan
noun
L-tryp·to·phan
ˈel-ˈtrip-tə-ˌfan 
: the levorotatory form of tryptophan that is a precursor of serotonin and was used formerly as a dietary supplement especially to promote sleep and relieve depression
Examples of L-tryptophan in a Sentence
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Not just another gourmet candy bar, the dark chocolate with lavender and blueberry flavors is infused with the hormone melatonin, the amino acid L-tryptophan, a blend of soothing botanicals and something called PharmaGABA, an artificial version of a neurotransmitter that calms the brain.
—
Karen Kaplan, Los Angeles Times, 4 Dec. 2024
This could be due to ingredients like ginger or L-tryptophan, which can irritate sensitive stomachs.
—Amber Smith, Discover Magazine, 5 Aug. 2023
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Karen Kaplan, Los Angeles Times, 4 Dec. 2024
This could be due to ingredients like ginger or L-tryptophan, which can irritate sensitive stomachs.
—Amber Smith, Discover Magazine, 5 Aug. 2023
Cite this Entry
“L-tryptophan.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/L-tryptophan. Accessed 31 Oct. 2025.
Copy CitationMedical Definition
L-tryptophan
noun
L-tryp·to·phan
ˈel-ˈtrip-tə-ˌfan
: the levorotatory form of tryptophan that is a precursor of serotonin and was formerly used in some health food preparations in the belief that it promoted sleep and relieved depression see eosinophilia-myalgia syndrome
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