Evaluation of cyclohexenoesculetin-beta-D-galactoside and 8-hydroxyquinoline-beta-D-galactoside as substrates for the detection of beta-galactosidase

We describe the synthesis of two new substrates for the detection of beta-galactosidase and evaluate their performance in comparison with that of 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal). Of 171 Enterobacteriaceae strains that were able to hydrolyze X-Gal, 166 (97.1%) also hydrolyzed cyclohesenocsculetin-beta-D-galactoside whereas only 96 (56.1%) showed evidence of hydrolysis of 8-hydroxyquinoline-beta-D-galactoside. No false-positive results were observed with either substrate.