Validation of a HPLC method for flavonoid biomarkers in skullcap (Scutellaria) and its use to illustrate wide variability in the quality of commercial tinctures.

PURPOSE: 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). CONCLUSION: 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.

Comparison of rosmarinic acid content in commercial tinctures produced from fresh and dried lemon balm (Melissa officinalis).

PURPOSE: To measure the rosmarinic acid content of eight commercial tinctures derived from fresh (n= 5) and dried (n=3) Melissa officinalis herb. METHODS: Rosmarinic acid and the internal standard (esculin) were purchased from Aldrich Chemical Co. The column used was a Luna C18, 5 um (150 x 4.6 mm I.D., Phenomenex) maintained at ambient room temperature. The HPLC system consisted of a Shimadzu SCL-6B controller, Shimadzu LC-6A pumps, Shimadzu SPD-6A UV single wavelength spectrophotometric detector set to 320 nm and Shimadzu SIL-6B autosampler. Gradient elution of the samples and standard were performed using ammonium formate (0.02 M; pH 6.25 at 27 oC; eluent A) and methanol (eluent B). The gradient elution initial conditions were 2% of eluent B with linear gradient to 60% at 30 min, followed by linear gradient to 90% of eluent B at 31 min, this proportion being maintained for 4 min. The column was then returned to the initial condition at 36 min and maintained until the end of the run at 43 min. The flow rate was 1 mL/min. The assay was validated for sensitivity, accuracy and reproducibility. RESULTS: The content of rosmarinic acid in commercial tinctures was significantly higher in the tinctures made from dried plant material (2.96 - 22.18 mg/mL) compared to fresh plant tinctures (