title: Bioassay-guided isolation of antioxidants from Astragalus altaicus by combination of chromatographic techniques.
abstract: An efficient method for bioassay-guided preparative isolation of antioxidants from the n-butanol extract of Astragalus altaicus Bunge was ingeniously developed by combination of silica gel column chromatography and high-speed counter-current chromatography. Under the bioassay-guidance of antioxidant activities, the antioxidants were gradually separated from the crude sample of Astragalus altaicus Bunge by silica gel column chromatography and high-speed counter-current chromatography. Silica gel column chromatography separation was performed with chloroform, chloroform-methanol (100:1~5:1, v/v) and chloroform-methanol-water (5:1:0.1~2:1:0.1, v/v/v). High-speed counter-current chromatography separation was performed with a two-phase solvent system composed of ethyl acetate-n-butanol-water (2:1:6, v/v/v), which was successfully selected by thin layer chromatography analysis, at a flow rate of 1.5 mL/min. As a result, isorhamnetin-3-gentiobioside (20.8 mg), rutin (82.0 mg), and narcissin (12.8 mg) were obtained for the first time from 200 mg of the crude sample, ABS-5 of Astragalus altaicus Bunge. The purities were all at over 95% by high-performance liquid chromatography analysis, and their structures were unambiguously identified by mass spectroscopy, (1) H, and (13) C nuclear magnetic resonance spectroscopy. Antioxidant activities of the three compounds were also assayed by in vitro ABTS [2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) diamonium salt] radical cation scavenging activity. Among them, rutin possessed the highest antioxidant capacity with SC(50) value of 22.15 μg/mL.
authors.affiliation: Key Laboratory of Xinjiang Indigenous Medicinal Plants Resource Utilization, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, China.
authors.forename: Chunyan
authors.initials: C
authors.lastname: Yang
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.forename: Haji Akber
authors.initials: HA
authors.lastname: Aisa
authors.forename: Xuelei
authors.initials: X
authors.lastname: Xin
authors.forename: Hairong
authors.initials: H
authors.lastname: Ma
authors.forename: Abulimiti
authors.initials: A
authors.lastname: Yili
authors.forename: Yongxin
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D000975:Antioxidants / Q000032:analysis / Q000302:isolation & purification*; D027883:Astragalus Plant / Q000737:chemistry*; D001681:Biological Assay / Q000379:methods*; D005591:Chemical Fractionation / Q000379:methods*; D002853:Chromatography, Liquid / Q000379:methods*; D010936:Plant Extracts / Q000032:analysis / Q000302:isolation & purification*
chemical_list: D000975:Antioxidants; D010936:Plant Extracts