Schistosomiasis may be caused by six different species of the genus Schistosoma. Current treatment is
based only on two drugs: oxamniquine, which is only effective against the Schistosoma mansoni species,
and praziquantel, which is ineffective against young parasites. Therefore, research on new drugs and
their targets for the treatment of this disease is urgently needed. In the present work, the efficacies of
several seaweeds extracts against S. mansoni were tested. Worm couples were incubated with different
concentration of seaweed extracts for 120 h and monitored after the first 2 h and then every 24 h to
evaluate death, mobility reduction and couple detachment. The extracts of 13 different seaweed species
were tested in a first trial and the active extracts were further evaluated in lower concentrations. The
extracts of Gracilaria ornata and species belonging to the genera Dictyota and Laurencia showed activity
at relatively low concentrations. The active extracts were analyzed by LC–MS, and possible candidates
are proposed.