A common pathway for metabolism of 4-hydroxybenzylglucosinolate in Pieris and Anthocaris (Lepidoptera: Pieridae)

Caterpillars of Pieris rapae L. (Lepidoptera: Pieridae) convert 4-hydroxybenzylglucosinolate (sinalbin) in brassicaceous plants into 4-hydroxybenzylcyanide sulfate (HBC sulfate), with 4-hydroxybenzylcyanide (HBC) as intermediate. This apparently serves as a detoxification, because alternative formation of a mustard oil is avoided. We confirmed the capacity of P. rapae to convert the intermediate HBC into HBC sulfate. Four additional Pieridae – Anthocaris cardamines L., Pieris virginiensis Harris, Pieris napi oleracea Edwards and Pieris brassicae L., likewise excreted HBC sulfate after ingesting leaves with topically added HBC or leaves naturally containing sinalbin and myrosinase, but not after ingesting control leaves devoid of HBC and sinalbin. We confirmed the capacity of the most distantly related pierid species (A. cardamines) for converting ingested (topically added) sinalbin into HBC sulfate. Larvae of two non-pierid Brassicaceae-feeding insects, the oligophagous sawfly Athalia rosae L. (Hymenoptera: Tenthrenidae) and the polyphagous moth Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), did not excrete HBC sulfate after ingesting sinalbin-containing leaves or topically added HBC.