Study of the amino acid composition of raw material of Oxytropis pilosa (L.) DC., growing in the Saratov region

Introduction. Amino acids (AAs) are key components of living organisms. Medicinal plants are valuable sources of AAs, which enhance the bioavailability of other metabolites and potentiate their pharmacological effects. However, the amino acid composition of many plants, including Oxytropis pilosa (L.) DC., remains unexplored.

Aim. To establish the qualitative and quantitative composition of free and bound amino acids in O. pilosa raw material growing in the Saratov region.

Materials and methods. O. pilosa raw material collected during the period of mass flowering in the Saratov region was used as the object of the study. Qualitative analysis of free AAs was performed by thin-layer chromatography (TLC) using an n-butanol – acetone – glacial acetic acid – water system (35 : 35 : 10 : 20) with 2 % ninhydrin in alcohol as the detection reagent. Quantitative determination of the total free AAs was carried out by spectrophotometry using a Shimadzu UV-1800 spectrophotometer (Japan) at an analytical wavelength of 568 nm. Qualitative and quantitative analysis of free and bound AAs was performed by HPLC on a Shimadzu LC-20 Prominence chromatograph equipped with an SPD-M20A detector (Japan), an SIL-20A autosampler, and LabSolutions data acquisition and processing software. Reference standards of AAs were used for compound identification. AA content was expressed in mg/g of dry raw material. The obtained data were statistically processed using MS Excel 2017.

Results and discussion. The composition of free AAs in aqueous extracts from the herb, flowers, and leaves of O. pilosa was determined by TLC. Six AAs (aspartic acid, proline, serine, threonine, valine, and isoleucine) were identified in all studied samples. The highest total free AA content was found in the herb of O. pilosa (30.70 ± 0.39 mg/g). HPLC analysis of AAs in the extract from the herb after preliminary hydrolysis revealed 15 AAs, among which the predominant ones were alanine (66.056 ± 0.584 mg/g), 4-hydroxyproline (25.912 ± 0.278 mg/g), proline (17.834 ± 0.168 mg/g), and histidine (13.030 ± 0.086 mg/g).

Conclusion. The qualitative and quantitative composition of free and bound AAs in O. pilosa raw material has been established for the first time. The total amino acid content was 165.659 ± 0.806 mg/g, with essential AAs accounting for 16.958 ± 0.139 mg/g.

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