Novel detection of formylated phloroglucinol compounds (FPCs) in the wound-associated wood of Eucalyptus globulus and E. nitens

This study characterized the chemical responses of Eucalyptus globulus and Eucalyptus nitens to artificial inoculation with a basidiomycete decay fungus. Nine-year-old trees responded to mechanical wounding or inoculation with the decay fungus by producing new wound wood characterized by the presence of dark extractives 17 months after wounding. Analysis of crude wound wood extracts by HPLC coupled to negative ion electrospray mass spectrometry revealed the presence of a complex mixture of many unidentified formylated phloroglucinol compounds (FPCs), in addition to a diverse range of other polyphenolic compounds (hydrolyzable tannins, proanthocyanidins, flavanone glycoside, stilbene glycosides). Prior to this study, FPCs have only been reported from leaves and buds of Eucalyptus spp. Unequivocal evidence for the presence of macrocarpal A and B, and sideroxylonal A and B in the crude extracts was obtained, as well as evidence for a wide range of as yet unreported FPCs. Subsequent preliminary in vitro fungal and bacterial bioassays did not support an antimicrobial role for FPCs in host-pathogen interactions in eucalypts.