The amino acid composition of knotweeds (Polygonum) of the series Amphibiae Kom

Introduction. The genus Polygonum (Persicaria Mill.) that belongs to the buckwheat family (Polygonaceae Juss.) is represented by a wide variety of species and types - from xerophytes to hydrophytes. The plant is widespread throughout Russia. Polygonum amphibium is a perennial herbaceous plant of the genus Polygonum. There are two known types: aquatic (P. amphibia (L.) Gray) and terrestrial (P. amphibia var. terrestris Delarbre) plants. According to the scientific literature, the aqueous plant has an antimicrobial effect and contains large amounts of phenolic compounds. There is insufficient information on the chemical composition of the terrestrial plant and the characteristics of its use in medicine. The composition of plant amino acids has not been investigated. Objective: to comparatively investigate the amino acid composition of two types of Polygonum amphibium (aquatic and terrestrial plants) stored in the Voronezh Region. Material and methods. The investigation objects were the dried samples of two types of Polygonum amphibium, which were stored in the coastal zone of the Voronezh River in the Voronezh Region in 2017. Free amino acids (AAs) were qualitatively analyzed by thin-layer chromatography (TLC) in the butanol : acetic acid : water (4 : 1 : 2) system; the detection reagent was a 0.2% alcoholic ninhydrin solution. The amount of free AAs was quantified by spectrophotometry by the ninhydrin reaction at an analytical maximum of 568 nm. The overall composition of AAs was determined by capillary electrophoresis. Results. Individual components were identified in the investigated types of Polygonum amphibium and differences were revealed in the profile of free AAs. Capillary electrophoresis could show that all the objects contained 17 AAs, of them 7 AAs were essential. Each sample exhibited AAs that were dominant in the composition of biologically active substances in the raw materials. The amount of free AAs in the aquatic type of Polygonum amphibium was found to account for 0.66%, which was 12% less than that in its terrestrial type. Conclusion. The composition of AAs in the investigated types of Polygonum amphibium indicates that the knotweed can be an additional source of AAs. The results of the investigation may be used when assessing the identity and high-quality of the weed of Polygonum amphibium.

Persicaria amphibia (L.) Gray, Persicaria amphibia var. terrestris Delarbre, amino acids, Polygonum amphibium (aquatic type), Persicaria amphibia (L.) Gray, Polygonum amphibium (terrestrial type), Persicaria amphibia var. terrestris Delarbre, TLC, capillary electrophoresis, spectrophotometry