6-Nitrofluorescein (isomer II) is widely used as a fluorescent probe in biochemical and cellular studies. Its strong fluorescence properties make it valuable for labeling and tracking molecules in various biological systems. It is often employed in fluorescence microscopy to visualize cellular structures and processes, providing insights into cell dynamics and interactions. Additionally, it serves as a pH-sensitive indicator, helping to measure and monitor pH changes in experimental setups. Its application extends to assays for enzyme activity, where it acts as a substrate or reporter molecule, enabling the detection of specific enzymatic reactions. This compound is also utilized in research involving oxidative stress, as it can be used to detect and quantify reactive oxygen species.