Labeling analysis of three neuropeptides（Met-enkephalin, Leu-enkephalin, and neurotensin） with 7-methoxycoumarin-3-carboxylic acid N-succinimidyl ester（MCSE） was investigated. The experimental conditions for labeling reaction and HPLC analysis of the neuropeptide derivatives were optimized. It was found that the labeling reatction could be achieved at 37 ℃ for one hour in H3BO3-NaCl-Na2B4O7 buffer（pH=8.3） with a labeling ratio of about 80%. The derivative mixture from the three peptides can be separated in a 40 min linear gradient from 60% to 20% of solvent A（100 mmol/L sodium acetate, pH=5.0） and from 40% to 80% of solvent B[60%（volume fraction） acetonitrile in water]. The resulting labeled products were also confirmed by MALDI-TOF-MS analysis. Compared with the native neuropeptides, the resulting labeled products have a longer absorption and fluorescence wavelengths, which is beneficial to the effective elimination of background fluorescence interference from biological matrix.
