Preparation of plant extracts
Wild, greenhouse-acclimatized and tissue culture-derived plants were seperated into aerial and underground parts, freeze-dried and lypholized. The ground materials (100 mg/mL) were homogenized with 80% methanol in a 2 mL Eppendorf, using an oscillation ball mill (MM 301, Retsch, Haan, Germany) at a frequency of 27 l/s for 3 min. The resultant extracts were centrifuged for 10 min at 20 000 rpm and the supernatant was retained for subsequent analysis.