Chromogenic hydroxyanthraquinone-based enzyme substrates for the detection of microbial β-d-galactosidase, β-d-glucuronidase and β-d-ribosidase.

Di-β-d-galactopyranoside derivatives of quinizarin (1,4-dihydroxyanthraquinone) and anthrarufin (1,5-dihydroxyanthraquinone) were evaluated as microbial enzyme substrates in Columbia agar medium for the detection of clinically important microorganisms. Furthermore, these substrates were evaluated both in the presence and absence of iron salts which could chelate to the aglycone after microbial hydrolysis of the substrate. The quinizarin-based substrate resulted in the formation of black microbial colonies in the presence of iron salts and orange colonies in their absence.