The amino acid composition of the herb of some Astragalus L. species

Introduction. The genus Astragalus L. belonging to the legume (Fabaceae) family is represented by a wide variety of life forms and has about 3000 species. Saponins, flavonoids, and polysaccharides are the main biologically active substances (BASs) of plants of the genus Astragalus. Among the related compounds, amino acids (AAs) that are widely distributed in nature and participate in the regulation of different life processes in plants and animals are of interest. The search for new promising sources of AAs generates scientific interest and has practical significance in expanding the range of officinal medicinal plant raw materials. From this point of view, it is relevant to investigate the amino acid composition of Astragalus herb and to quantify this group of BASs in the examined samples. Objective: to comparatively study the amino acid composition of five Astragalus species growing in the Saratov Region Material and methods. The investigation objects were the herb samples of Astragalus henningii (Stev.) Klok., Astragalus varius S.G. Gmel., Astragalus testiculatus Pall., Astragalus dasyanthus Pall., and Astragalus zingeri Korsh., which had been collected in the Saratov Region in 2020–2021. Qualitative analysis was carried out using thin-layer chemical chromatography (TLC) in the n-butanol – glacial acetic acid – water (35:35:10:20) system. The reagent for detection was a 2% ninhydrin ethanol solution. The amount of free AAs was measured by a spectrophotometric method on a SHIMADZU UV-1800 spectrophotometer (Japan) at an analytical wavelength of 568 nm. Results. TLC was used to determine the amino acid composition of the aqueous extracts of the herb of the examined Astragalus species. Asparagine and proline were detected in all the samples analyzed. Nine amino acids, eight of which were significantly identified as arginine, asparagine, proline, glutamic acid, threonine, valine, methionine, and phenylalanine, were first found in the extracts from the herb of Astragalus henningii (Stev.) Klok., Astragalus varius S.G. Gmel., and Astragalus testiculatus Pall. The highest content of AAs was established to be in the aqueous extract from the herb of Astragalus henningii (Stev.) Klok. (5.50%) and Astragalus testiculatus Pall. (5.23%) and the lowest one was in Astragalus zingeri Korsh. (1.67%). Conclusion. The composition and quantification of the content of AAs in the examined samples show that the herb of these plants along with other BASs may be a promising source of AAs. The findings of this investigation can be used when assessing the identity and high quality of the herb of the Astragalus species analyzed.