Used as a chromogenic substrate in microbiological assays for the detection of enzyme activity, particularly for α-glucosidase. When the glycosidic bond is cleaved by the enzyme, it releases an indoxyl derivative that undergoes oxidation to form a blue-colored indigo pigment. This color change allows for easy visual or spectrophotometric detection, making it valuable in bacterial identification, enzyme screening, and diagnostic applications. Commonly employed in culture media to differentiate microbial species based on enzymatic activity.