Centric 322 a

STSs (50 mg/mL) from rhizomes were prepared separately. Powdered lyophilized plant material was dispersed in 4 mL of 70% aqueous acetone. The resulting suspension was vortexed (1 min at 2800 rpm; IKA lab dancer, Sigma-Aldrich) and then centrifuged at 4500 rpm (Centric 322 A, Tehtnica, Železniki, Slovenia) for 5 min. The supernatant was fil tered through a 0.45 µm polyvinylidene fluoride (PVDF) membrane filter (Millipore, Billerica, MA, USA) into amber glass storage vials, which were stored at −20 °C. After thawing, smaller particles were present on the bottom of some STSs’ vials. The solutions were then centrifuged for 3 min at 13,400 rpm (MiniSpin centrifuge, MiniSpin, Eppendorf, Hamburg, Germany) and the supernatants (STSs from rhizomes of all three knotweeds) were transferred into GC vials. These undiluted STSs were then used for HPTLC and HPTLC–MS/MS analyses.

STSs (50 mg/mL) from leaves were prepared separately by dispersing 200 mg of powdered lyophilized plant material in 4 mL of 70% aqueous acetone followed. Suspension was vortexed (1 min at 2800 rpm; IKA lab dancer, Sigma-Aldrich) and then centrifuged at 4500 rpm (Centric 322 A, Tehtnica, Železniki, Slovenia) for 5 min. Supernatant was filtered through a 0.45 µm polyvinylidene fluoride (PVDF) membrane filter (Millipore, Billerica, MA, USA). The obtained supernatants were stored in an amber glass storage vial at −20 °C. Due to smaller particles that appeared on the bottom of some STSs vials after thawing, those solutions were centrifuged for 3 min at 13,400 rpm (MiniSpin centrifuge, MiniSpin, Eppendorf, Hamburg, Germany). Supernatants (STSs from leaves of all knotweeds) were transferred into GC vials and were used undiluted for HPTLC and HPTLC-MS/MS analyses.