L-NIL is primarily used in research settings to study the role of nitric oxide synthase (NOS) in various biological processes. It is a selective inhibitor of inducible nitric oxide synthase (iNOS), making it valuable in investigating inflammatory diseases, as iNOS is often upregulated during inflammation. Researchers use L-NIL to explore its potential therapeutic effects in conditions like arthritis, sepsis, and neurodegenerative disorders where excessive nitric oxide production contributes to tissue damage. Additionally, it aids in understanding the mechanisms of immune response and vascular function, providing insights into drug development for inflammatory and autoimmune diseases.