Antiplasmodial activity of alkaloids from Croton linearis leaves

Croton linearis is a shrub that grows in Caribbean regions, which is rich in metabolites such as alkaloids. The main aim of this study was to evaluate the antiplasmodial effect of alkaloids from this species. Three isoquinoline alkaloids, i.e. reticuline (1), laudanidine (2) and 8,14-dihydrosalutaridine (3), were isolated from the leaves of C. linearis by flash chromatography and semi-preparative HPLC-DAD-MS. Their structures were elucidated by spectroscopic techniques. Antiplasmodial activity against the chloroquine-resistant strain Plasmodium falciparum K1 and cytotoxicity against MRC-5 cells (human fetal lung fibroblast cells) were assessed in vitro. Reticuline, laudanidine and 8,14-dihydrosalutaridine showed moderate antiplasmodial activity with IC₅₀ values of 46.8 ± 0.6, 17.7 ± 0.6 and 16.0 ± 0.5 μM, respectively, but no cytotoxicity was observed in a concentration up to 64.0 μM. This is the first report on the antiplasmodial activity of laudanidine and 8,14-dihydrosalutaridine.