MOBILITY INHIBITION AND NEMATOCIDAL ACTIVITY OF ASARONE AND RELATED PHENYLPROPANOIDS ON 2ND-STAGE LARVAE OF TOXOCARA-CANIS

The in vitro effect of asarone, the nematocidal principle of the rhizo me of Acorus calamus, on second-stage larvae of Toxocara canis is comp osed of two independent actions: one is a fast acting inhibition of th e larval mobility and the other is a slow acting larvicidal action. Mo bility of the larvae was rapidly inhibited when they were incubated wi th asarone. Dye exclusion assay revealed that larvae were alive at thi s stage, and their mobility was restored after the first inhibition, s uggesting that this effect was temporary and reversible. However, when the mobility decreased again during prolonged incubation, the cellula r viability of larvae disappeared, showing that they were killed by th e compound. The above two-stage effect of asarone was almost identical in two geometrical isomers ((E)- and (Z)-asarone). Di- and tri-methox ypropenyl or propylbenzenes carrying tao methoxy groups at a vicinal p osition on a benzene ring showed, more or less, a two-stage effect of this type. These two actions were suggested to be separable by an appr opriate modification of the structure.