Londershausen_1991_Pest.Sci_33_427

Extracts of ground seeds from Annona squamosa revealed interesting insecticidal properties. By an activity-monitored fractionation, different acetogenins, called annonins and annonacin, were determined to be the active components. The investigation of ATP-levels (at the LT50 value) in Plutella xylostella under treatment with annonin I and antimycin A revealed values of 1.45 and 1.35 umole g-1 fresh weight respectively, whereas insecticides primarily afecting neurotoxic targets, e.g. cyfluthrin (sodium channels; 2.25 umole g-1 fresh weight) or parathion (acetylcholinesterase; 2.0 umole g-1 fresh weight) did not influence the ATP-levels significantly (control; 1.98 umole g-1 fresh weight). Further studies on the target site of annonins revealed an inhibitory effect on the NADH-cytochrome c-reductase and complex I of insect mitochondria with IC50 values of 4-8 nmole mg-1 protein and 0.8 uM respectively for annonin I. Similar results were observed for the inhibition of complex I from bovine heart muscle (IC50: <0.1 uM) or Neurospora crassa cells (IC50: 0.3 uM), whereas coupling sites II or III were not afected. Furthermore, annonins did not reveal any direct inhibition of oxidative phosphorylation or uncoupling efects.