Fig. 4

HPLC chromatogram of eight organic acids are presented as standards: glucuronic acid (peak 1), gluconic acid (peak 2), D-saccharic acid 1,4-lactone (DSL) (peak 3), L-ascorbic acid (peak 4), lactic acid (peak 5), acetic acid (peak 6), citric acid (peak 7), and succinic acid (peak 8).