Kynurenine and kynurenic acid: Two human neuromodulators found in Cannabis sativa L.

L-Kynurenine (KYN) and kynurenic acid (KYNA) are products of the metabolism of L-tryptophan (TRP) in the central nervous system of animals, but they are not commonly found in plants. In particular, KYNA is known for its interesting pharmacological properties (anti-oxidative, anti-inflammatory, hypolipidemic, and neuroprotective), which suggest a potential functional food ingredient role. The three compounds were identified in samples of Cannabis sativa L. by means of high-performance liquid chromatography coupled to high-resolution mass spectrometry using an untargeted metabolomics approach. Their concentrations were evaluated using a targeted metabolomics method in three organs of the plant (roots, stem, and leaves) in soil at two different growth stages and in hydroponics conditions. The distribution of TRP, KYN and KYNA was found tendentially higher in leaves compared to stem and roots and changed over time. Moreover, the levels of KYNA found in this study are unprecedentedly high compared to those found so far in other plant species, suggesting that Cannabis sativa L. could be a promising alternative source of this metabolite.