Nile red

Nile red
IUPAC name 9-diethylamino-5-benzo[α]phenoxazinone
Other names Nile red, Nile blue oxazone
Identifiers
CAS number	7385-67-3 Y
PubChem	65182
ChemSpider	58681 Y
ChEBI	CHEBI:52169 N
ChEMBL	CHEMBL144472 Y
Jmol-3D images	Image 1
SMILES CCN(CC)c1ccc2c(c1)oc-3cc(=O)c4ccccc4c3n2
InChI InChI=1S/C20H18N2O2/c1-3-22(4-2)13-9-10-16-18(11-13)24-19-12-17(23)14-7-5-6-8-15(14)20(19)21-16/h5-12H,3-4H2,1-2H3 Y Key: VOFUROIFQGPCGE-UHFFFAOYSA-N Y InChI=1/C20H18N2O2/c1-3-22(4-2)13-9-10-16-18(11-13)24-19-12-17(23)14-7-5-6-8-15(14)20(19)21-16/h5-12H,3-4H2,1-2H3 Key: VOFUROIFQGPCGE-UHFFFAOYAM
Properties
Molecular formula	C20H18N2O2
Molar mass	318.369 g/mol
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Nile red under visible and ultraviolet (366 nm) light in different solvents
From left to right: 1. water, 2. methanol, 3. ethanol, 4. acetonitrile, 5. dimethylformamide, 6. acetone, 7. ethyl acetate, 8. dichloromethane, 9. n-hexane, 10. methyl-tert-butylether, 11. cyclohexane, 12. toluene.

Nile red (also known as Nile blue oxazone) is a lipophilic stain. It is produced by boiling a solution of Nile blue with sulfuric acid.^[1] As can be seen from the structural formulae, this process replaces an amino group with a carbonyl group. Nile red stains intracellular lipid droplets red. In most polar solvents Nile Red will not fluoresce, however when in a lipid-rich environment can be intensely fluorescent, with varying colours from deep red to strong yellow-gold emission. It excites at 485 nm, and emits at 525 nm (552/636 nm in methanol), the fluorescence of the dye is heavily dependent on the solvent used.

Since the reaction to generate Nile red does not usually completely exhaust the supply of Nile blue, additional separation steps are required if pure Nile red is needed.

References

1. ^ SD Fowler and P Greenspan (1985). "Application of Nile red, a fluorescent hydrophobic probe, for the detection of neutral lipid deposits in tissue sections: comparison with oil red O". Journal of Histochemistry and Cytochemistry 33 (8): 833–836.