2.3. HPLC sample preparation
The artificially dried roots were ground using an electric mill
with a 2 mm pore size. The finely powdered root material
(10 mg) was extracted with 10 ml methanol by sonication
(45 min, at room temperature) by obtaining a drug/extract ratio
of 35.2% (w/w). After centrifugation at 5000 rpm for 10 min with
a Thermo Scientific IEC CL10 Centrifuge from Thermo Electron
Industries SAS (Chateau-Gontier, France), the extracts were transferred
to a 10 ml volumetric flask, which was then filled up to
the final volume with extraction solvent. The sample solutions
were filtered through a 0.45 lm pore size nylon membrane filter
(Phenex, Phenomenex, Torrance, CA, USA) before injection into
the HPLC. All samples were stored in a refrigerator at the temperature
of 4 C until analysis. Each sample was analysed in triplicate.