Presence of kynurenic acid in alcoholic beverages - Is this good news, or bad news?

Kynurenic acid (KYNA) is a metabolite of tryptophan formed enzymatically along kynurenine pathway in bacteria, fungi, plants and animals. It was suggested that yeast may produce KYNA during the fermentation process. Since KYNA was found to interact with alcohol metabolism by inhibition of aldehyde dehydrogenase activity the aim of this study was to measure the content of KYNA in selected alcoholic beverages of various type, beer, wine, mead and spirits. Moreover, the absorption and elimination rate of KYNA administered as a beverage was investigated in humans. Twelve healthy volunteers (6 female and 6 male) were studied. Fifty six samples of alcoholic beverages were of commercial origin. KYNA was determined by means of high-performance liquid chromatography method with fluorometric detection. KYNA was identified in all studied beverages. The amounts of KYNA found in various types of beverages differed significantly: mead 9.4-38.1 µg/100 ml, wine 1.4-10.9 µg/100 ml, beer 0.1-5.2 µg/100 ml, spirits 0.01-0.1 µg/100 ml. In human, it was found that KYNA is rapidly absorbed from digestive tract reaching its maximal concentration in blood 30 min after administration. Thus, the potential interaction between KYNA and alcohol occurring in human body after ingestion of alcoholic beverages was proven.

Fate and distribution of kynurenic acid administered as beverage.

BACKGROUND: Kynurenic acid (KYNA) is a biologically active metabolite of tryptophan exerting action on several receptors located in the brain and periphery. KYNA can be synthesized endogenously or supplied in the diet. It was documented that KYNA is present in various types of food. However, its presence in beverages was not yet investigated. Here, we measured content of KYNA in tea and coffee as well as analyzed distribution and fate of intragastrically administered labelled KYNA in mice. METHODS: 16 and 13 studied samples of tea and coffee, respectively were of commercial origin. Tea and coffee infusions were prepared according to the producers' guidelines. KYNA content in beverages was measured by means of HPLC detection. Adult male mice were used for analysis of fate of intragastrically administered labelled KYNA and collected samples were analyzed using liquid scintillation counter. RESULTS: KYNA was identified in all studied beverages. Amounts of KYNA found in various types of beverages differed significantly. The highest content of KYNA in tea and coffee was 8.7 µg/100 ml and 0.63 µg/100 ml, respectively. It was found that KYNA administered intragastrically as a liquid is absorbed from the digestive system and readily excreted in urine. The atypical kinetics of KYNA distribution were found in intestinal content of cecum, where it appeared later and persisted longer than in other tissues. CONCLUSIONS: Our data show that tea and coffee intake may contribute to KYNA content in the human organism. The distribution pattern of KYNA delivered as a liquid suggests that it either directly affects digestive system's functioning and intestinal microbiome composition, or participates in the whole body pool of KYNA.