Abstract

Eucalyptus pellita F. Muell., a high-yielding timber species commercially planted in many clonal plantations in North Sumatra, Indonesia has been exploited only for its wood, but the leaf biomasses are relatively understudied for their bioactivity. The aim of this study was to investigate the potential secondary metabolites in E. pellita leaf extracts to support its future utilization other than timber production. Crude extracts were obtained by maceration technique using ethyl acetate, hexane, and methanol then each fraction was analyzed for phytochemical contents (phenolics, flavonoids), total antioxidant capacity, antioxidant activity (2,2-diphenyl-1-picrylhydrazyl/DPPH radical scavenging) and antibacterial activity against Bacillus subtilis, Escherichia coli and Staphylococcus aureus. Compounds were isolated and purified using column chromatography and preparative thin-layer chromatography (TLC), following their structural elucidation and characterization based on UV-Vis, FT-IR, and 1H-NMR outputs. The ethyl acetate fraction among the fractions revealed the highest phenolic (205.2 mg GAE/g of extract) and flavonoid (44.7 mg QE/g of extract) contents and strongest antioxidant activity (IC50 = 62.55 µg/mL). The n-hexane fraction produced the largest inhibition zones (15.5–19.2 mm), followed by the ethyl acetate fraction (14.8–15.1 mm) and the methanolic fraction (10.1–13.2 mm) against the tested bacteria. Structural analysis resulted in the identification of cudracusisoflavone, an isoflavone, as the major compound in the ethyl acetate fraction. These findings promote the use of E. pellita leaves as a rich source of bioactive phytochemicals, especially cudracusisoflavone which can be utilized for drug development.