Abstract: The leaf essential oil of Platycladus orientalis obtained by hydro-distillation was investigated by GC and GC-MS. 8-Propoxy cedrane (15.41%), terpinen-4-ol (12.98%), α-pinene (9.85%), sabenene (9.92%), and 3-carene (6.77%) were the major compounds of the 29 identified components which accounted for 96.64% of the total oil of P. orientalis. The oil was rich in monoterpenoids and sesquiterpenoids. It was assayed to have the broad spectral antibacterial activity with the MBC values ranged from 0.10 mg/mL to 1.0 mg/mL, the MIC values from 0.063 mg/mL to 0.90 mg/mL, and the IC50 values from 0.044 mg/mL to 0.763 mg/mL. The essential oil was subjected to the screening for the antioxidant activity by ferrozine-Fe2+ complex formation and β-carotene bleaching inhibition assays. It inhibited both the formation of ferrozine-Fe2+ complex and β-carotene-linoleic acid oxidation in a dose dependent manner with the IC₅₀ values of 0.409 mg/mL and 0.526 mg/mL, respectively.

Key words: Platycladus orientalis, essential oil, chemical composition, antibacterial activity, antioxidant activity