Journal of Chemical Ecology

, Volume 15, Issue 9, pp 2347–2355

Induction of cytochrome P450-mediated detoxification of xanthotoxin in the black swallowtail


  • Michael B. Cohen
    • Department of EntomologyUniversity of Illinois
  • May R. Berenbaum
    • Department of EntomologyUniversity of Illinois
  • Mary A. Schuler
    • Department of Plant BiologyUniversity of Illinois

DOI: 10.1007/BF01012086

Cite this article as:
Cohen, M.B., Berenbaum, M.R. & Schuler, M.A. J Chem Ecol (1989) 15: 2347. doi:10.1007/BF01012086


Xanthotoxin is a phototoxic allomone found in many of the host plants of the black swallowtail,Papilio polyxenes (Lepidoptera: Papilionidae). When added to the diet of final instar larvae, xanthotoxin can induce the cytochrome P450 monooxygenase (P450) activity in midgut microsomes by which it is detoxified. Induction is dose-dependent, increasing sevenfold when larvae feed on parsley treated topically with xanthotoxin at 0.5 or 1.0% fresh weight. Although xanthotoxin exerts much of its toxic effects when photoactivated by ultraviolet light, induction of P450 activity did not differ in the presence or absence of ultraviolet light. Despite a 4.7-fold induction of xanthotoxin-metabolizing P450 activity, total P450 content measured in the same microsomal samples did not increase significantly. These data indicate that multiple forms of P450 exist in the black swallowtail midgut and that they are differentially induced by xanthotoxin.

Key words

Black swallowtailPapilio polyxenesLepidopteraPapilionidaemicrosomal cytochrome P450inductionxanthotoxinfuranocoumarinsplant defensive compounds

Copyright information

© Plenum Publishing Corporation 1989