In vitro antibacterial, antifungal and antioxidant activities of Eucalyptus spp. leaf extracts related to phenolic composition

The crude methanolic extracts from leaves of Eucalyptus camaldulensis L., E. camaldulensis var obtusa and E. gomphocephala grown in Egypt were investigated to explore their chemical composition as well as their antibacterial, antifungal and antioxidant activities. Major phenolics found were ellagic acid, quercetin 3-O-rhamnoside, quercetin 3-O-b-D-glucuronide, caffeic acid and chlorogenic acid. The antioxidant activities were examined by the 2,2′-diphenypicrylhydrazyl (DPPH) and β-Carotene-linoleic acid assays. E. camaldulensis extracts showed the highest phenolic content, antioxidant and antimicrobial activities compared to other cultivars. MIC values reported for antibacterial activity of E. camaldulensis ranged from 0.08 μg/mL (Bacillus cereus) to 0.22 μg/mL (Staphylococcus aureus), while MBC values ranged from 0.16 μg/mL (Dickeya solani and B. cereus) to 0.40 μg/mL (S. aureus). The inhibitory activities against growth of bacteria and fungi used is an indication that E. camaldulensis a might be useful resource for the development and formulation of antibacterial and antifungal drugs.