In vitro metabolism of a linear furanocoumarin (8-methoxypsoralen, xanthotoxin) by mixed-function oxidases of larvae of black swallowtail butterfly and fall armyworm.

Studies were made of the comparative in vitro metabolism of [(14)C]xanthotoxin and [(14)C]aldrin by homogenate preparations of midguts and bodies (carcass minus digestive tract and head) of last-stage larvae of the black swallowtail butterfly (Papilio polyxenes Fabr.) and the fall armyworm [Spodoptera frugiperda (J. E. Smith)]. The two substrates were metabolized by 10,000g supernatant microsomal preparations from both species. Evidence gained through the use of a specific inhibitor and cofactor indicated that mixed-function microsomal oxidases were major factors in the metabolism and that the specific activity of this enzyme system was considerably higher in midgut preparations fromP. polyxenes than in similar preparations fromS. frugiperda. Aldrin was metabolized 3-4 times faster byP. polyxenes, and xanthotoxin 6-6.5 times faster.