Evaluation of phytochemical, antibacterial and antioxidant activity on Astragalus crysostachysBoiss roots

Astragalus is a well-known genus in Leguminosae family that represented more than 800 species growing in Iran. Nevertheless, there are a few reports on Astragalus plants endemic to Iran. The roots of Astragalus plants are rich in saponins, flavonoids and polysaccharides that possess various pharmacological activities. In present study, Chemical components, antioxidant and antibacterial activity of Astragalus crysostachys Boiss. roots were evaluated. For determination of phytochemicals in Astragalus chrysostachys Boiss. roots, total hydroalcoholic extract was fractionated with ethyl acetate and n-butanol. Ethyl acetate extract as a flavonoid rich extract was analyzed using vacuum liquid chromatography and preparative TLC and consequently a major flavonoid was isolated. The structure of the obtained compound was elucidated with 1D and 2D NMR experiments. Additionally, the essential oil of the roots was analyzed by GC-MS. Antioxidant activity of all extracts was evaluated by different assays. Moreover, antibacterial activities of the extracts were also investigated against 2 Gram-positive and 2 Gram-negative bacteria using Micro-dilution Broth method. Apigenin-6, 8-di-C-glucoside was detected in ethyl acetate extract for the first time in genus Astragalus. In addition, m-tolualdehyde, acetophenone, croweacin were found to be characteristics of the volatile oil of roots. Ethyl acetate extract revealed notable antioxidant activity in DPPH scavenging assay with IC50 value of 14.6 µg/mL. Evaluation of antibacterial activity on the tested extracts showed mild activity against Gram-positive bacteria. Since there have been no reports on Astragalus crysostachys Boiss. to date, the present data might be promising for application of this plant derivatives in phytotherapeutic practice.