Antifungal Potential of biobased oils from Citrus sinensis Peels and Eucalyptus globulus leaves in vitro against fungal isolates

Abstract

Biobased oils found in the leaves of many plants used as coating materials for the preservation of fruits influence the handling of citrus fruits. The effectiveness of these oils on the target organisms is associated with the ability to develop resistant strains. In the present study the antifungal activity of the biobased oils obtained from orange peel and eucalyptus leaves against Aspergillus niger, Aspergillus flavus, Rhizomucor pusillus and Penicillium citrinium was tested at various concentrations in vitro. Sample fruits showing signs of decay during postharvest storage were selected for isolation and identification of the fungi. A serial dilution method was applied at 10 fold for fungi isolates and concentrations were plated onto Potato Dextrose Agar (PDA) media 15 mL. The plates were incubated at room temperature (28 °C) and observed every 24 hrs for possible microbial growth. The pour plate method was used to investigate the antifungal activity of the oils on the test fungi in vitro. The results indicate a continuous decline in the inhibition of the biobased oil treatment during the period of inoculation. The interaction effect of the different biobased oil, their concentrations and the different isolates was significant (P ? 0.05) from day 1 to day 7 during the inoculation. The combined orange peels and eucalyptus leaves at 100% concentration recorded (69.35%) as the highest percent of inhibition which was significantly higher than all other interactions. The least percent inhibition was found with orange peels biobased oil at 1:1 v/v concentration against Aspergillus flavus (24.23 %). Biobased oils at full strength from eucalyptus combined with oil from orange peels demonstrated significant potential against Penicillium citrinium. This research revealed the potential antifungal properties in vitro of the biobased oils against pathogenic fungi. These findings provide the basis for the application of combined biobased oil as an effective antifungal remedy against pathogenic fungi.