Alcohol extraction of botanical dietary supplements was performed because it mimics industrial and research conditions [24].
Methanol extracts were obtained using a modification of the previously described procedure [25]. For each phytopharmaceutical
preparation, a total of 10 tablets were weighed and made into a fine
powder or the contents of 10 capsules were emptied and weighed. An
accurately weighed portion of the contents equivalent to one tablet or
capsule was extracted with 25 mL of 70% aqueous methanol using a
sonicator (WUC-D06H Ultrasonic Sonicator, Daihan Scientific, Korea)
for 30 min. The sample solutions were then filtered through 0.45-mm
disposable filters. The general procedures for the HPLC method
described under calibration (Section 2.4) were followed, and the
concentrations of EGC, CAF, EC, B2 and EGCG were calculated.