Estragole: An acute toxic principle from the volatile oil of the leaves of clausena anisata

The toxicity of the volatile oil of the leaves of Clausena anisata Hook. f. (Rutaceae) to variegated grasshopper Zonocerus variegatus L. is reported. The plant species has a strong, aromatic odor compared by some to aniseed and by others to garlic (1). Its uses in some parts of Africa and the Phillipines had earlier been reviewed (1). One of the many uses is the burning of the dried plant to repel mosquitoes. Novak also demonstrated that the volatiles from the leaves of the plant had repellent activities against a tick, Ixodes ricimus (2). Steam distillation of the fresh leaves yielded a strong, sweet-smelling, brownish-yellow oil. Acute toxicity tests on the oil showed that it was toxic to the third nymphal instar of the grasshopper. Chromatography led to the isolation of estragole (the major component of the oil) which was l¹/₂ times more toxic than the crude oil. This represents the first report of the biological activity of this compound. Furthermore, its isolation as the major compound from the volatile oil of the leaves of this plant contradicts the earlier report of anethole as the major constituent (1).