Bioassay-guided study of the ethanol extract from the cashew Anacardium occidentale furnished cardol triene (1), cardol diene (2), anacardic acid triene (3), cardol monoene (4), anacardic acid diene (5), 2-methylcardol triene (6), and 2-methylcardol diene (7). 1D- and 2D-NMR experiments and HRMS analysis confirmed the structures of compounds 1-7. Compounds 2 and 7 were active against Schistosoma mansoni adult worms in vitro, with LC50 values of 32.2 and 14.5 μM and selectivity indices of 6.1 and 21.2, respectively. Scanning electron microscopy of the tegument of male worms in the presence of compound 7 at 25 μM after 24 h of incubation showed severe damage as well as peeling and reduction in the number of spine tubercles. Transmission electron microscopy analyses revealed swollen mitochondrial membrane, vacuoles, and altered tegument in worms incubated with compound 2 (25 μM after 24 h). Worms incubated with compound 7 (25 μM after 24 h) had lysed interstitial tissue, degenerated mitochondria, and drastically altered tegument. Together, the results indicated that compound 7 presents promising in vitro schistosomicidal activity.
Keywords: alkyl-phenols; cashew Anacardium occidentale; schistosomicidal activity.