Pyrrolizidine alkaloids in the pericopine moth scearctia figulina (Erebidae: Arctiinae): metabolism and chemical defense

Pyrrolizidine alkaloids (PAs) are defensive compounds present in several plant families. However, some specialist herbivore insects have overcome these toxic compounds and sequester PAs converted to N-oxide as a defense against predators and a precursor of male sexual pheromones. In this context, we investigated PA sequestration by the specialist pericopine moth Scearctia figulina (Erebidae: Arctiinae), which feeds on leaves of Heliotropium transalpinum (Boraginaceae) as larvae. Additionally, we examined the role of PAs against different predators. The PAs sequestered from the host plant were metabolized by larvae and transferred to adults via two main pathways: (i) rinderine and its acetyl derivative (7S, 3' R) were epimerized to intermedine (7R, 3' R) and lycopsamine (7R, 3' S), and (ii) insect PAs were biosynthesized from necine bases obtained from plant-acquired PAs, with necic acids of insect origin. Both metabolic products may be related to the biosynthesis of 7R male pheromone and to chemical defense. Larvae and adults were chemically protected against the spiders Nephila clavipes and Lycosa erythrognatha and the chick Gallus gallus, and this defense may be associated to PAs27814371443CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP306103/2013-32011/17708-