Bioassay-guided fractionation, GC–MS identification and in vitro evaluation of antioxidant and antimicrobial activities of bioactive compounds from Eucalyptus globulus stump wood methanolic extract

Abstract The biomass of Eucalyptus globulus , and particularly the stump wood, has received increased attention in recent years, including in a biorefinery perspective. A previous work evaluated the crude methanolic extract of E. globulus stump wood regarding its potential antioxidant and antimicrobial properties. That work concluded that E. globulus stump wood could be considered as a source of bioactive polyphenols. In the present study, the crude methanolic extract of E. globulus stump wood was thus fractionated in order to isolate the components responsible for such biological properties. This extract was subjected to bioassay-guided fractionation and the antioxidant and antimicrobial properties of the fractions were then evaluated. The antioxidant activity was assessed by the DPPH scavenging assay and the antimicrobial properties were studied by bioautography and resazurin microtiter methods. The fractions presented considerable capacity to scavenge the DPPH free radicals and to inhibit the growth of bacterial and yeast strains. The results obtained for the fractions were even better than the ones obtained with the crude extract. The GC–MS analysis revealed that the major compounds present in the extract were gallic acid, ellagic acid, citramalic acid and citric acid.