Determination of Bioactive Compound Kynurenic Acid in Linum usitatissimum L.

Kynurenic acid (KYNA) is a bioactive compound exhibiting multiple actions and positive effects on human health due to its antioxidant, anti-inflammatory and neuroprotective properties. KYNA has been found to have a beneficial effect on wound healing and the prevention of scarring. Despite notable progress in the research focused on KYNA observed during the last 10 years, KYNA's presence in flax (Linum usitatissimum L.) has not been proven to date. In the present study, parts of flax plants were analysed for KYNA synthesis. Moreover, eight different cultivars of flax seeds were tested for the presence of KYNA, resulting in a maximum of 0.432 µg/g FW in the seeds of the cultivar Jan. The level of KYNA was also tested in the 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 levels of 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 tryptophan. A spectroscopic analysis of KYNA was performed using the FTIR/ATR method. It was found that, in tested samples, the characteristic KYNA vibration bands overlap with the bands corresponding to the vibrations of biopolymers (especially pectin and cellulose) present in flax plants and fibres.