PYRROLIZIDINE ALKALOIDS IN CHROMOLAENA-ODORATA - CHEMICAL AND CHEMOECOLOGICAL ASPECTS

The tropical weed Chromolaena odorata contains the N-oxides of five pyrrolizidine alkaloids (PAs):7-and 9-angeloylretronecine, intermedine, rinderine and 3'-acetylrinderine. Highest concentrations occur in roots and mature flower heads, while leaves and stems are almost devoid of alkaloids, and no PAs are present in nectar. The polyphagous grasshopper Zonocerus variegatus sequesters intermedine and rinderine from Chromolaena flowers and transforms up to 20% of these PAs into lycopsamine and echinatine, respectively, by inversion of configuration at C-3'. Pure rinderine injected into the haemolymph of Zonocerus is partly converted into intermedine, indicating inversion of configuration at C-7.