| Summary: | From a bioactive methanolic extract of <i>Senecio fistulosus</i>, the antifeedant effects of the alkaloidal and non-alkaloidal fractions were tested against the insects <i>Spodoptera littoralis</i>, <i>Myzus persicae</i> and <i>Rhopalosiphum padi</i>, with the non-alkaloidal fraction being antifeedant. The phytochemical study of the non-alkaloidal fraction of <i>S. fistulosus</i>, resulted in the isolation of four compounds, two 9-oxo-furanoeremophilanes (<b>1</b>, <b>2</b>), an eremophilanolide, 1β,10β-epoxy-6-acetoxy-8α-hydroxy-eremofil-7(11)-en-8β,12-olide (<b>3</b>) and a maaliol derivative (<b>4</b>). The alkaloidal fraction yielded two known pyrrolizidine alkaloids (<b>5</b>, <b>6</b>). Compounds <b>1</b>, <b>3</b> and <b>4</b> are new natural products. Furanoeremophilane <b>2</b> was a strong antifeedant against <i>S. littoralis</i> and maaliane <b>4</b> inhibited the settling of <i>M. persicae</i>.
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