Coptisine acts as a nucleolus fluorescent probe in vitro.

Coptisine (COP) is a natural protoberberine isoquinoline alkaloid that is isolated from Coptis chinensis and exhibits a variety of pharmacological activities, such as the inhibition of tumor growth, bacterial infection, inflammation and oxidative stress. In this study, COP penetrated and produced fluorescent signals in living tumor cell lines, primary MEF cells and polyformaldehyde-fixed cells. The fluorescent signal was detected at a wavelength of 488 nm. The fluorescent signal of COP was observed predominantly in the nucleoli and colocalized with nucleolus fibrillarin and B23. The fluorescence intensity of COP was associated with tumor malignancy. Compared with cells with high fluorescent signals, cells with low fluorescent signals were highly malignant. Taken together, these data suggest that COP can function as a nucleolus probe and a probe candidate for distinguishing tumor cell malignancy.