Phenylazonaphtol-b-D-O-Glucoside 3 was prepared starting from p-nitrophenyl glucoside which was subjected to hydrogenolysis providing the p-aminophenyl glucoside 1. Further condensation with 2-naphtol sodium salt under weak acidic diazonium salt conditions afforded  Phenylazonaphtol-b-D-O-Glucoside 2, which was deprotected providing the target glucoside 3. The resulting glucoside was assayed as substrate for detection of b-glycosidase activity and its hydrolytic activity determined through the UV absorption of the released chromophore.