Anti-Toxoplasma gondii screening of eight species used in Côte d’Ivoire, and bio-guided isolation of three previously undescribed nor-sesquiterpenoids and one benzyl glycoside from Elaeis guineensis leaves

The apicomplexan parasite Toxoplasma gondii causes toxoplasmosis, a ubiquitous and cosmopolitan parasitosis, generally asymptomatic and potentially dangerous for the fetus and highly immunocompromised patients. Pyrimethamine and sulfadiazine, supplemented with folic acid, are the drugs of choice to treating the disease, but they produce severe side effects and treatments fail due to drug resistance. New anti-Toxoplasma compounds are needed, and natural compounds can be a good source for obtaining them. The antiparasitic activity of 40 polar and non-polar extracts of eight antiparasitic medicinal plants used in Côte d'Ivoire, and selected based on ethnopharmacological survey, were evaluated in vitro against T. gondii. Among them, the hydromethanolic extract of the Elaeis guineensis leaves exhibited the best parasite growth inhibition (94% ± 0.07) at 25 μg/mL without being cytotoxic at the same dose. The fractionation of this extract did not allow the recovery of antitoxoplasmic activity in its individualized fractions. The 13C-NMR based dereplication of this extract and the purification of two fractions highlighted the presence of saccharides (1-2), aliphatic acids (3 and 8-11), cardanols (12-13), triterpene (14), sterol (15), nor-sesquiterpene (16), megastigman derivatives (7 and 17-19), glycosylated benzyl (20-21), flavonoids (4-6 and 22), pseudoalkaloid (23), and allyl glycoside (24). Nine compounds 1-9 were identified during the dereplication process, whereas fifteen compounds 10-24 were identified after purification and four of them were undescribed (16-18 and 20). A synergistic effect between these metabolites is thought to be responsible for the anti-Toxoplasma activity. However, further studies should be carried out to confirm and explain this synergistic or antagonistic effect between the identified compounds.