effects of tannin and extracts of and on the exsheathment of infective larvae of .

(Euphorbiaceae) and (Rubiaceae) are two plants of the beninese pharmacopeia used for the control of gastrointestinal nematodes (GINs) in small ruminants. The objective of the present study is to explore the mechanism of bioactive compounds involved in the action of these two plants on the third-stage infective larvae (L3s) of . Thus, sheathed L3s of were incubated with acetone extracts of and at concentrations of 0, 150, 300, 600 and 1200 µg/mL for 3 h at 25°C. The L3s were then washed and artificially submitted to exsheathment in the presence of sodium hypochlorite solution. The role of tannins was verified by adding a tannin inhibitor, polyvinyl polypyrrolidone (PVPP), to the acetone extracts of these two plants for 2 h at 25°C. Acetone extracts from and inhibited the exsheathment of larvae ( < 0.001) and this inhibitory effect was dose-dependent for at the concentrations tested. Treatment of and extracts with PVPP was associated with a partial restoration of the exsheathment kinetics of larvae ( < 0.001), confirming the predominant role of tannins but also the residual role of other secondary metabolites. These results suggest that these plants are endowed with anthelmintic (AHs) properties and therefore likely to be used as alternatives to synthetic molecules.