Novel derivatives of niclosamide synthesis: Its bioactivity and interaction with Schistosoma japonicum cercariae

Two novel niclosamide derivatives were synthesized by adding polyethylene glycol groups of differing lengths to a niclosamide core. The modified niclosamide derivatives were characterized using 1H NMR and HRMS spectra. Anti-cercarial bioactivity results showed that the niclosamide derivative constructed to float on the surface of the water was able to kill cercariae when the number of hydrophilic groups was >3. A fluorescent niclosamide derivative containing naphthalimide was further synthesized to observe the interaction between the cercaricide and Schistosoma japonicum cercariae. Confocal fluorescence microscopy revealed that the fluorescent niclosamide derivative could easily penetrate into the cercarial body beyond the circulatory system leading to the rapid death of cercariae.