The use of herbal medicines is common among people living in rural areas and increasingly popular in urbanized countries. Kynurenic acid (KYNA) is a metabolite of kynurenine possessing anti-inflammatory, anti-oxidative and pain reliving properties. Previous data indicated that the content of KYNA in the synovial fluid of patients with rheumatoid arthritis is lower than in patients with osteoarthritis. Rheumatoid arthritis is a chronic, systemic inflammatory disorder affecting about 1% of the world's population.
The aim of the presented study was to investigate the content of KYNA in 11 herbal preparations used in rheumatic diseases.
The following herbs were studied: bean pericarp, birch leaf, dandelion root, elder flower, horsetail herb, nettle leaf, peppermint leaf and willow bark. An anti-rheumatic mixture of the herbs Reumatefix and Reumaflos tea were also investigated. The herbs were prepared according to producers' directions. In addition, the herbal supplement Devil's Claw containing root of Harpagophytum was used. KYNA content was measured using the high-performance liquid chromatography method, and KYNA was detected fluorometrically.
KYNA was found in all studied herbal preparations. The highest content of KYNA was found in peppermint, nettle, birch leaf and the horsetail herb. The lowest content of KYNA was found in willow bark, dandelion root and in the extract from the root of Harpagophytum.
These findings indicate that the use of herbal preparations containing a high level of KYNA can be considered as a supplementary measure in rheumatoid arthritis therapy, as well as in rheumatic diseases prevention.