title: Validation of a HPLC method for flavonoid biomarkers in skullcap (Scutellaria) and its use to illustrate wide variability in the quality of commercial tinctures.
abstract: OBJECTIVE
  To compare the flavonoid biomarker content (baicalin, baicalein and wogonin) of eleven commercial tinctures derived from Scutellaria lateriflora aerial parts (n=7) and Scutellaria baicalensis root (n=4). S. lateriflora tinctures are used in by western herbal practitioners to treat anxiety whereas S. baicalensis tinctures are used to treat inflammatory disease.
  
  
  METHODS
  Baicalin and baicalein were purchased from Aldrich Chemical Co. and Wogonin was purchased from ChromaDex. The internal standard (4-hydroxybenzoic acid) was obtained from Acros Organics. The column used was a Luna C18, 5 m (150 x 4.6 mm, Phenomenex) maintained at ambient room temperature. A HP1050 HPLC system was used, comprising a gradient pump with degasser, a variable wavelength UV detector set to 270 nm, and an autosampler. Gradient elution was performed using 0.1% formic acid (eluent A) and methanol (eluent B). The gradient elution initial conditions were 45% B with linear gradient to 60% from 2 to 10 min, followed by linear gradient to 70% B at 30 min, and then linear gradient to 99% B at 31 min, this proportion being maintained for 1 min. The mobile phase was then returned to initial conditions at 33 min and maintained until the end of the run at 35 min. The flow rate was 1 mL/min. The assay was validated for sensitivity, accuracy and reproducibility.
  
  
  RESULTS
  The concentration range of biomarkers (baicalin, baicalein and wogonin) in commercial tinctures is reported for S. lateriflora (baicalin: 0-12.66 mg/mL; baicalein: 0-0.63 mg/mL; wogonin: 0-0.16 mg/mL) and for S. baicalensis (baicalin: 0.12-10.61 mg/mL; baicalein: 0.52-5.88 mg/mL; wogonin: 0.08-1.61 mg/mL).
  
  
  CONCLUSIONS
  The wide variability in biomarker concentrations between commercial tinctures has important implications for the manufacturers of commercial tinctures, for herbal practitioners in the choice of tinctures and not least for pharmacology and clinical researchers.
authors.affiliation: Medicines Research Group, School of Health and Bioscience, University of East London, Stratford, London UK.
authors.forename: Jiayu
authors.initials: J
authors.lastname: Gao
authors.forename: Alberto
authors.initials: A
authors.lastname: Sanchez-Medina
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Pendry
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hughes
authors.forename: Geoffrey P
authors.initials: GP
authors.lastname: Webb
authors.forename: Olivia
authors.initials: O
authors.lastname: Corcoran
mesh_terms: D015415:Biomarkers / Q000032:analysis / Q000737:chemistry; D002626:Chemistry, Pharmaceutical / Q000379:methods / Q000592:standards*; D002851:Chromatography, High Pressure Liquid / Q000379:methods / Q000592:standards; D005419:Flavonoids / Q000032:analysis* / Q000737:chemistry* / Q000592:standards; D035261:Plant Components, Aerial; D010936:Plant Extracts / Q000737:chemistry; D018517:Plant Roots; D031363:Scutellaria
chemical_list: D015415:Biomarkers; D005419:Flavonoids; D010936:Plant Extracts