Anti-insect Activity of Bufadienolides from Urginea maritima

Squill [Urginea maritima (L.) Baker, Liliaceae] is a native medicinal and ornamental plant from the Mediterranean area. The bulbs were an ancient source of rodenticide products replaced later on by warfarin and modern anticoagulant raticides. Since rats have developed resistance to such products there is now renewed interest in the species. In the 1950s, attempts were made in the United States to introduce this new crop for arid lands. A collection of bulbs are still maintained at Gentry Experimental Farm, Murrieta, California. Some limitations concerning variability in toxicity were previously discussed (Verbiscar et al. 1986a; Gentry et al. 1987). Scilliroside, a high toxicity bufadienolide glycoside, is the main active principle. Other glycosides and aglycones have also been isolated from the bulb (Verbiscar et al. 1986b). We tested this plant in our research program to screen botanicals for insecticidal activity at “Centro de Investigacion y Desarrollo Agroalimentario” in Murcia, Spain. In Spain squill is a wild plant of coastal areas (Fig. 1). Ethanolic extracts of bulbs have been active against stored product pests (Pascual-Villalobos and Fernandez 1999), although such anti-insect effects could not be attributed to specific compounds in that study. The objective of this work was to test pure bufadienolides isolated from U. maritima.