Nile red is a lipophilic stain. It stains intracellular lipid droplets. Nile red is also intensely fluorescent, with a strong yellow-gold emission if included into a lipid-rich environment.
Nile Red is an organic heterotetracyclic compound that is 5H-benzo[a]phenoxazin-5-one substituted at position 9 by a diethylamino group.
Nile Red is an uncharged hydrophobic molecule and a benzophenoxazone dye. It functions as a fluorescent probe for intracellular lipids and hydrophobic domains of proteins. This dye is fluorescent in all organic solvents. Its fluorescence colors range from golden yellow to deep red.
Using the 1,3-Naphthalenediol Approach to synthsis Nile red. To a solution of 1,3-naphthalenediol (0.50 g, 3.12 mmol) in anhydrous DMF (25 mL) was added 4-nitroso-N,N-diethylaniline (0.56 g, 3.12 mmol). This reaction mixture was stirred at 80 °C (DrySyn heating block) for 16 h and concentrated under reduced pressure. The crude product was purified by flash chromatography (0?50% EtOAc in hexanes) to obtain Nile Red, which crystallized from hexanes in green crystals (0.80 g, 2.50 mmol). Yield: 80%[1].
[1] Mick Hornum*. “Substituted 9-Diethylaminobenzo[a]phenoxazin-5-ones (Nile Red Analogues): Synthesis and Photophysical Properties.” The Journal of Organic Chemistry 86 2 (2020): 1471–1488.
