Relationship between chemical functional groups on Eucalyptus secondary metabolites and their effectiveness as marsupial antifeedants

Eucalyptus displays strong intraspecific variation in resistance to browsin g by marsupial folivores that can be attributed to variation in the concent ration and type of diformylphloroglucinol compounds (DFPCs) in the foliage. In this study, we ask which functional groups of diformylphloroglucinol co mpounds determine their effectiveness in deterring feeding. We used a simpl e and highly deterrent compound, jensenone, as a model DFPC and compared it s activity to structural variants that differ in the types of functional gr oups on the phloroglucinol molecule. Torquatone, a naturally occurring comp ound in the steam Volatile fraction of Eucalyptus torquata foliage, has nei ther the aldehyde nor phenol groups that are believed to contribute to the antifeedant actions of jensenone. From the naturally occurring compounds we have synthesized two intermediates, a capped phenol/free aldehyde compound (acetyl-jensenone) and a free phenol/no aldehyde compound (demethyl-torqua tone). Addition of jensenone and acetyl-jensenone to diets of common ringta il possums (Pseudocheirus peregrinus) substantially reduced their food inta kes. Torquatone showed less activity, and there was little reduction in foo d intake when demethyl-torquatone was added to the diet. We conclude that a t least the aldehyde groups attached to the aromatic nucleus are important in determining whether these compounds deter feeding by common ringtail pos sums, whereas the phenol groups may play only a minor role.