title: A validated UHPLC-tandem mass spectrometry method for quantitative analysis of flavonolignans in milk thistle (Silybum marianum) extracts.
abstract: Validated methods are needed for the analysis of natural product secondary metabolites. These methods are particularly important to translate in vitro observations to in vivo studies. Herein, a method is reported for the analysis of the key secondary metabolites, a series of flavonolignans and a flavonoid, from an extract prepared from the seeds of milk thistle [Silybum marianum (L.) Gaertn. (Asteraceae)]. This report represents the first UHPLC MS-MS method validated for quantitative analysis of these compounds. The method takes advantage of the excellent resolution achievable with UHPLC to provide a complete analysis in less than 7min. The method is validated using both UV and MS detectors, making it applicable in laboratories with different types of analytical instrumentation available. Lower limits of quantitation achieved with this method range from 0.0400μM to 0.160μM with UV and from 0.0800μM to 0.160μM with MS. The new method is employed to evaluate variability in constituent composition in various commercial S. marianum extracts, and to show that storage of the milk thistle compounds in DMSO leads to degradation.
authors.affiliation: Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, 27402, USA.
authors.forename: Tyler N
authors.initials: TN
authors.lastname: Graf
authors.affiliation: Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, 27402, USA.
authors.forename: Nadja B
authors.initials: NB
authors.lastname: Cech
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, WA, 98104, USA; Department of Global Health, University of Washington, Seattle, WA, 98104, USA; Department of Microbiology, University of Washington, Seattle, WA, 98104, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Polyak
authors.affiliation: Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, 27402, USA. Electronic address: nicholas_oberlies@uncg.edu.
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Oberlies
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D005419:Flavonoids / Q000032:analysis / Q000302:isolation & purification; D044947:Flavonolignans / Q000032:analysis* / Q000302:isolation & purification; D057230:Limit of Detection; D020944:Silybum marianum / Q000737:chemistry*; D010936:Plant Extracts / Q000032:analysis / Q000737:chemistry; D012639:Seeds; D012997:Solvents / Q000737:chemistry; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D005419:Flavonoids; D044947:Flavonolignans; D010936:Plant Extracts; D012997:Solvents; D004121:Dimethyl Sulfoxide
keywords: Flavonolignans; Milk thistle; Silybum marianum; Silymarin; Validation