Effects of hycanthone and praziquantel on monoamine oxidase and cholinesterases in Schistosoma mansoni.

The effects of hycanthone and praziquantel on the activities of monoamine oxidases and cholinesterases were studied in the 600-g supernatant from homogenates of Schistosoma mansoni and mouse liver or brain. Hycanthone was shown to be a very potent inhibitor of monoamine oxidases from worms and mouse liver. Hycanthone also inhibited the specific and nonspecific cholinesterases of S. mansoni, but cholinesterase from mouse brain was not affected significantly by this drug. Praziquantel showed no effect on monoamine oxidase from mouse liver or the parasite; however, it was slightly inhibitory to S. mansoni cholinesterases at very high concentrations. Mouse brain cholinesterase required an even higher concentration of praziquantel to observe inhibition. The inhibition of monoamine oxidase in S. mansoni by hycanthone adds a new mode of action to our knowledge of this compound, and suggests another possibility for the development of future anthelminthics.