Eucalyptus leaf byproduct inhibits the anthracnose-causing fungus Colletotrichum gloeosporioides

Colletotrichum gloeosporioides is a major anthracnose-causing agent, causing dark spots in important fruit crops such as banana, papaya and mango. Eucalyptus trees and shrubs are native to Australia, but are currently widely distributed. There is evidence that Eucalyptus species display activity against Colletotrichum gloeosporioides. In this work, the antifungal activity of essential oils and ethanolic extracts of three Eucalyptus species cultivated for wood in Colombia (Eucalyptus camaldulensis Dehn., Eucalyptus globulus Labill. and Eucalyptus tereticornis Smith.)was evaluated. Leaf from the three Eucalyptus species was extracted by hydrodistillation and ethanol maceration to yield respectively the essential oil and ethanolic extract, which were tested against C. gloeosporioides Penz., using an agar macrodilution assay. Ethanolic extracts showed stronger inhibition than essential oils. Although the ethanolic extract of E. camaldulensis provided 98 percent of inhibition at a concentration of 5000 mg/L, the ethanolic extract of E. globulus inhibited by 50 percent at a lower concentration of 500 mg/L. The metabolites from essential oils and ethanol extracts were examined respectively by gas chromatography coupled to mass spectrometry (GC-MS)and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Both E. camaldulensis and E. globulus ethanolic extracts may be considered for antifungal formulations and as source of interesting anti-Colletotrichum compounds.