Determination of kynurenic acid in Linum usitatissimum L.

Abstract Kynurenic acid (KYNA) is a bioactive compound exhibiting positive effects on human health due to its antioxidant, anti-inflammatory and anti-virus properties. Despite notable progress in the research focused on KYNA observed during the last 10 years, KYNA presence in flax (Linum usitatissimum L.) has not been proven so far. In the present study, parts of flax plants were analysed for KYNA synthesis. Moreover, eight different cultivars of flax seeds were tested for KYNA presence, resulting in maximally 0.432 µg/g FW in the seeds of the cultivar Jan. The level of KYNA was also tested in stems and roots of two selected flax cultivars: an oily cultivar (Linola) and a fibrous cultivar (Nike). The exposure of plants to the KYNA precursors tryptophan and kynurenine resulted in higher KYNA accumulation in flax shoots and roots. Thus, the obtained results indicate that KYNA might be synthesized in flax. The highest amount of KYNA (295.9 µg/g dry weight [DW]) was detected in flax roots derived from plants grown in tissue cultures supplemented with 10 mM tryptophan. The content of KYNA in flax cultivated on tryptophan-enriched medium was about 90-fold higher than in potato tubers and 600-fold higher than in flax seeds in the present study. These data suggest that flax tissue cultures enriched with tryptophan might be an efficient source of KYNA.