Loadings (mean ± standard deviation) of PC 1 and PC 2 of a PCA on metabolic fingerprints of the different pre-treatment methods (see Figure 1). Plantago lanceolata leaf material was either extracted directly, frozen in liquid nitrogen, lyophilised or air-dried for 24 hours at room temperature, before further extraction in 100% methanol. Extracts were analysed by HPLC. Number of replicates N = 5; air-dried samples N = 3. Differences among pre-treatments were tested with ANOVA followed by Tukey's HSD tests. Different upper case letters indicate significantly different scores of PC 1 (F3,14 = 3.121, P < 0.05); lower case letters indicate significantly different scores of PC 2 (F3,14 = 4.238, P < 0.01).