Antifeedant activity of plant extracts and of new natural diglyceride compounds isolated from Ajuga pseudoiva leaves against Spodoptera littoralis larvae

Antifeedant activity of 215 natural extracts prepared from a range of medicinal plants growing in Tunisia, against larvae of Egyptian cotton leafworm. Spodoptera littoralis (Lepidoptera) has been studied. Feeding inhibition occurs with 35 extracts, of which 18 have been prepared from leaves. We also found potent antifeedant activity of petroleum ether, methylene chloride, acetone and methanol extracts of Olea europea stem barks. An active mixture of three new 1,3-diglyceride homologous compounds, ivaides A-C (I-III), was isolated from acetone extract of Ajuga pseudoiva leaves by chromatographic techniques guided by bioassay-positive responses. The behavioral response of Spodoptera littoralis larvae to these new natural compounds showed that significant activity might be associated with the presence in each of two beta -hydroxy-alkanoic moieties. This conclusion is reinforced by previous work showing the existence of 3-hydroxy-alkanoic acids and their derivatives in some biological systems and their production by micro-organisms. (C) 2001 Elsevier Science B.V. All rights reserved.