For HPLC analysis, samples were stopped with ice-cooled deionized water and freeze-thawed. After centrifugation (21,500 ×g, 4 °C, 15 min), samples were analyzed with a KNAUER Azura or Agilent 1200 system using a Phenomenex (Aschaffenburg, Germany) reversed phase Kinetex EVO C18 column (250 × 4.6 mm) as previously described . Briefly, samples were measured at 260 nm and 34 °C with a flow rate of 1 mL min -1 . Isocratic elution was performed using 80% A (0.1 M KH 2 PO 4 /K 2 HPO 4 , 8 mM tetrabutylammonium bisulfate, pH ca. 5.4) and 20% B (70% A, 30% MeOH) for 4 min followed by a gradient to 40% A and 60% B over 10 min, to 38% A and 62% B in 12 min and back to 80% A and 20% B in 0.5 min. Initial conditions were maintained for 2.5 min.