A new substrate to measure laccase activities in complex environments: Application to litters

Measuring laccase activities in natural environments requires improvement since this oxidation usually produces radical compounds which can interfere with other molecules from these complex media, leading to misinterpretation of the results. Here the syringaldazine skeleton was used to synthesise a new substrate whose quinone is soluble in water and chemically stable. Hydrophilic moieties were added to syringaldazine at the 3 and 5 positions on both aromatic rings to enhance its solubility in water. Syringaldazine analogue 6c was selected. Laccases from two white-rot fungus strains were first tested and a strong affinity for this substrate was observed. Moreover the laccase activity found using a litter extract was higher with 6c which can be explained by the strong stability of its quinone in water.