From the Italian scientists who first found THCp and CDBh in cannabis plants comes another discovery. Researchers discovered tryptophan and its active metabolites, including l-kynurenine acid and kynurenic acid, in cannabis. (1) Anyone who remembers the sleepy feeling after Thanksgiving turkey might have heard that tryptophan causes sedation.

Cannabinoids and terpenes are two big classes of active compounds in cannabis. And cannabinoids are a special type of terpenoid. Beyond the terps exists several other groups of important molecules including flavonoids and esters. Less discussed, is the composition of amino acids in cannabis plants.

Tryptophan is found in various foods, but unlike cannabis, plants rarely metabolize the amino acid to KYN or KYNa.

Tryptophan and its metabolites, a Thanksgiving tradition

Parmesan cheese and turkey are good sources of the amino acid — tryptophan. As it turns out, cannabis appears to be a richer source of this amino acid and its metabolites, l-kynurenine (KYN) and kynurenic acid (KYNa). Importantly, the latter of the two facilitates therapeutic properties. Therefore, the first discovery of tryptophan and it’s metabolites in cannabis plants delves into the secrets of the entourage (or ensemble) theory for edibles.

Adding to this, serotonin but also melatonin are products of tryptophan. Melatonin production is what causes food rich in tryptophan, possibly even hemp and cannabis leaves, to encourage better sleep. As it turns out, different amino acids in turkey interrupt tryptophan’s absorption into the body. For turkey dinner, sedation rather occurs after the big meal alters blood flow.

In the leaves — cannabis growth conditions and tryptophan

Hemp leaves were consistently more potent with amino acids relative to roots and stems, (1) which is not the same case for triterpenes. (2) Research funded by the Italian Ministry found further deep variations in the potency of tryptophan dependent on growth conditions. Yet, soil-grown and hydroponic cannabis cultivations both had remarkable amounts of tryptophan’s two metabolites — KYN and KYNa. (1)

Tryptophan is a precursor for several important neurotransmitters.

Animals cannot synthesize tryptophan and require plants to acquire it. At the same time, plants poorly break the amino acid down to KYN or KYNa. Instead, plants tend to absorb the metabolites through their roots from soil microbes. For this reason, the quantity of KYN and KYNa in cannabis was considered unprecedented in the study funded by The Italian Ministry of Education, Universities and Research.

In plants, KNY and KYNa might have protective properties against certain toxins. For humans, though, the metabolites have been shown to possess protective properties for the brain and heart. Anti-oxidant and anti-inflammatory effects might be involved with it’s protective functions. Beyond this, tryptophan metabolites have great potential for regulating lipids and attenuating obesity.

Let us know in the comments if you think the Italian researchers should be allowed to analyze tryptophan in cannabis flowers next. And stay tuned to learn more about the anti-inflammatory properties of cannabis root extract next week.

This story was updated on May 25, 2022, to better interpret the cause of sedation after eating turkey.

Show their work

  • The researchers cultivated plants into early and late vegetative stage from certified hemp seeds using strict growing procedures for the hydroponic experiment.
  • Hemp samples from open-field cultivations were collected for the soil-grown test.
  • Tryptophan and it’s metabolites are polar compounds, which the researchers employed standard techniques for extraction.
  • Extracts of hemp samples were analyzed using Ultra-high-preformance-liquid-chromatography in conjunction with an Ultra-High-Resolution-Mass Spectrometer.


  1. Russo F, Tolomeo F, Vandelli MA, et al. Kynurenine and kynurenic acid: Two human neuromodulators found in Cannabis sativa L. J Pharm Biomed Anal. 2022;211:114636. doi:10.1016/j.jpba.2022.114636
  2. Kim YN, Sim KS, Park S, Sohn HY, Kim T, Kim JH. In Vitro and In Vivo Anti-Inflammatory Effects of Cannabis sativa Stem Extract. J Med Food. 2022;25(4):408-417. doi:10.1089/jmf.2021.K.0200