Figure 2

Principal component analysis (PCA) of the relative metabolite amounts obtained after different extraction methods. The PCA was created by PAST (Palaeontological Statistics). PAST settings were as follows: Matrix: Var-covar and Boot N: 0 .A) PCA of all GC-MS based results of the extraction efficiency tests. a (red): boiling ethanol, b (black): cooled methanol, c) (purple): cooled ethanol, d (dark blue): boiling water, e (green): methanol-chlorofom-water-mixture, f (cyan): acetonitrile, g (light blue): 1M formic acid (Principal component (PC)1: 93.35% variance and PC2: 4.76% variance) B) PCA of the GC-MS based result for the extraction power of a) boiling ethanol, b) cooled methanol, c) cooled ethanol (PC1: 63.90% variance and PC2: 18.66% variance).