Compounds from Diospyros canaliculata (Ebenaceae) and their Antiparasitic Activities

Abstract

Aims: Discovering new lead compounds against parasitic diseases is a crucial step to ensuring a sustainable global pipeline for new effective drugs. This study focus on the isolation and the antiparasitic screening of secondary metabolites of the dichloromethane-methanol (1:1) extract of the stem bark of Diospyros canaliculata which showed antiprotozoal activity in vitro during preliminary screening. Study Design: According to the literature, plants of the genus Diospyros are potential sources of antiparasitic secondary metabolites. As far as we know, extracts from D. caniculata have not yet been investigated for their antiparasitic activity. Methodology: The air-dried and ground stem bark of Diospyros canaliculata was extracted at room temperature with a mixture of dichloromethane-methanol (1:1). The extract was concentrated to dryness under vacuum and the residue was subjected to repeated column chromatographic separation. The structures of the isolates were established by means of spectroscopic methods. These compounds were screened in vitro for their activity against four parasitic protozoa: Plasmodium falciparum, Leishmania donovani, Trypanosoma brucei rhodesiense and Trypanosoma cruzi and for their cytotoxic potential on mammalian cells. Results: The dichloromethane-methanol (1:1) extract of the stem bark of D. canaliculata showed antiprotozoal activity in vitro during preliminary screening. Phytochemical investigation of this extract led to the isolation of a new coumarinyl naphtoquinone canaliculin (1) together with the known canaliculatin (2), betulin (3), plumbagin (4), ismailin (5), gerberinol (6) and betulinic acid (7). Compounds 2-7 were evaluated in vitro for their antiprotozoal activities against P. falciparum (NF54), L. donovani, T. b. rhodesiense and T. cruzi. Plumbagin (4) exhibited good activity against all the tested strains with IC50 below 0,9 µg/mL while other tested compounds exhibited weak to moderate activity, generally with limited selectivity. Conclusion: From the present study, we infer that the dichloromethane-methanol (1:1) extract of the stem bark of D. canaliculata contains antiparasitic compounds. Unfortunately, the antiparasitic potency of these compounds may reflect general toxicity, as shown by their low IC50 recorded against the mammalian cell line