Evaluation of Oxasqualenoids from the Red Alga against .

genus is a widely distributed and opportunistic parasite with increasing importance worldwide as an emerging pathogen in the past decades. This protozoan has an active trophozoite stage， a cyst stage， and is dormant and very resistant. It can cause keratitis， an ocular sight-threatening disease， and granulomatous amoebic encephalitis， a chronic， very fatal brain pathology. In this study， the amoebicidal activity of sixteen oxasqualenoid metabolites and semisynthetic derivatives were tested against Neff. The results obtained point out that iubol () and dehydrothyrsiferol () possess potent activities， with IC values of 5.30 and 12.83 µM， respectively. The hydroxylated congeners thyrsiferol () and 22-hydroxydehydrothyrsiferol ()， active in the same value range at IC 13.97 and 17.00 µM， are not toxic against murine macrophages; thus， they are solid candidates for the development of new amoebicidal therapies.