First record of pyrrolizidine alkaloids in the southern African biotype of Chromolaena odorata (Asteraceae).

• Alkaloids were detected in the leaves of southern African biotype of C. odorata by Mayor's and Dragendorff's reagents. • The main alkaloids were two epimeric pyrrolizidine N -oxides rinderine and intermidine. • Alkaloids in the leaves varied significantly in sites with and without specialist herbivore P. insulata. • Thin-layer chromatography did not demonstrate differences in alkaloids in the roots collected from sites with and without P. insulata. • Gas Chromatography-Mass Spectrometry identified rinderine N -oxides and intermidine N -oxides in the roots of SAB C. odorata. • One directional proton nuclear magnetic resonance analysis was used to confirm the structures of rinderine and intermidine. Pyrrolizidine alkaloids (PAs) are amino alcohols, often esterified with mono- or dicarboxylic acids, found in several plant families, including the Asteraceae. Pyrrolizidine alkaloids are used for plant defence against generalist invertebrate herbivores. However, specialist herbivores that are able to sequester PAs from the host plant species derive a number of benefits from these defence compounds. This study investigated alkaloids and PAs from the leaves and roots of the southern African biotype (SAB) of Chromolaena odorata in different regions and habitats in South Africa, with and without the specialist herbivore Pareuchaetes insulata. Alkaloid N -oxides were initially detected in leaf samples by Mayor's and Dragendorff's reagents and later by thin-layer chromatography on root samples with detection by successive treatment with acetic anhydride and Ehrlich's reagent. Two pyrrolizidine alkaloids, rinderine and the stereoisomer intermidine, were isolated from the reduced root extract of the SAB C. odorata and identified by Gas Chromatography-Mass Spectrometry. The structures and configuration of the compounds were confirmed by chemical and spectroscopic methods, especially one-dimensional 1H Nuclear Magnetic Resonance analysis. Pyrrolizidine alkaloids are known to be used by arctiine moths to find their host plant and are sequestered for mating purposes, and furthermore, these compounds render these lepidopterans unpalatable to predators. This study is the first to detect the presence of alkaloids and pyrrolizidine alkaloids in the SAB C. odorata. [ABSTRACT FROM AUTHOR]