In vitro effects of the polyphenols resveratrol, mangiferin and (-)-epigallocatechin-3-gallate on the scuticociliate fish pathogen Philasterides dicentrarchi

This study investigated the in vitro effects of the polyphenols resveratrol, mangiferin and (-)-epigallocatechin-3-gallate (EGCG) on the histiophagous ciliate Philasterides dicentrarchi, which causes fatal scuticociliatosis in farmed turbot Scophthalmus maximus L. Of the 3 polyphenols, resveratrol showed strongest antiprotozoal activity, reducing ciliate density after 1 wk culture by, on average, 91 % at 50 muM, and 96 % at 500 muM. EGCG reduced ciliate density by, on average, 93 % at 500 muM, with no significant effect at 50 muM. Mangiferin reduced ciliate density by, on average, 56 % at 500 muM, again with no significant effect at 50 muM. In view of these findings, we discuss the potential utility of chemotherapy with polyphenols as a strategy for the control of scuticociliatosis in farmed turbot.