Astragalus gymnolobus, A. leporinus var. hirsutus, and A. onobrychis: Phytochemical analysis and biological activity

Astragalus is a genus with many important medicinal plant species. The historical background of Astragalus species dates back to 2000-3000 years. In this study, it was aimed to investigate the phytochemical composition, antioxidant, tyrosinase and alpha-amylase inhibitory activities of the MeOH (methanol) extracts obtained from three different Astragalus species (A. gymnolobus Fisch., A. leporinus Boiss. var. hirsutus (Post) D.F. Chamb., and A. onobrychis L.). It was understood that A. gymnolobus and A. onobrychis extracts are richer than A. leporinus var. hirsutusin terms of phenolics and flavonoids. According to the results of Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometry (LC-ESI-MS/MS) analysis, it was determined that hesperidin and hyperoside were found in high amounts in the extracts. A strong correlation was found between the phytochemical compositions of the plants and their antioxidant activities. The order of the antioxidant activity of A. gymnolobus from strongest to the weakest was as follows: Ferric Reducing Ability of Plasma (FRAP) (1.13 mg/mL), ferrous ion chelating (1.53 mg/mL), Cupric Reducing Antioxidant Capacity (CUPRAC) (1.58 mg/mL), 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) (2.52 mg/mL), phosphomolybdenum (2.91 mg/mL), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) (3.86 mg/mL). In the case of A. onobrychis, the order of the antioxidant activity was found to be: FRAP (1.25 mg/mL), ferrous ion chelating assays (1.69 mg/mL), CUPRAC (1.93 mg/mL), ABTS (2.21 mg/mL), phosphomolybdenum (2.77 mg/mL), and DPPH (4.50 mg/mL). A. gymnolobus (1.27 mg/mL, 281.92 mg KAEs/g extract) and A. onobrychis (1.25 mg/mL, 287.89 mg KAEs/g extract) have also been found to be effective tyrosinase inhibitors. In a-amylase inhibitory activity test, A. leporinus var. hirsutus was found to show the highest activity (4.06 mg/mL, 298.54 mg ACEs/g extract). According to Pearson correlation test results, it was concluded that hesperidin significantly contributed to the biological activities of the extracts.