The present study aimed to examine the chemical compositions of the essential oils of Beilschmiedia madang and their antioxidant, antibacterial, antifungal, anticholinesterase and anti-tyrosinase activities. The major constituents of the essential oils of leaf and bark of B. madang were δ-cadinene (17.0 and 20.5 %), β-caryophyllene (10.3 and 6.7 %), α-cubebene (11.3 and 15.6 %), and α-cadinol (5.8 and 10.6 %). The essential oils were screened for their antioxidant activities using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, β-carotene/linoleic acid bleaching, and total phenolic content. The bark oil showed the highest β-carotene/linoleic acid bleaching (90.3 % ± 0.2) and DPPH radical scavenging (IC50 212.0 µg/mL), while the highest phenolic content was exhibited by the leaf oil (94.5 % ± 0.3 mg GA/g). The antibacterial and antifungal activities were investigated by the disc diffusion and micro dilution method. The leaf and bark oils showed moderate activity towards Bacillus subtilis and Staphylococcus aureus with minimum inhibitory concentration (MIC) value 125 µg/mL. For antifungal assay, the bark oil showed strong activity towards Aspergillus niger and Aspergillus fumigatus with MIC value 62.5 µg/mL. Anticholinesterase and anti-tyrosinase activities were evaluated against Ellman method and mushroom tyrosinase, respectively. The results showed that leaf oil gave significant percentage inhibition (I%: acetylcholinesterase 55.2 %, butyrylcholinesterase 60.4 %, tyrosinase 53.1 %).
