Thuja Orientalis (L) (Platycladus orientalis) belongs to the family of Cupressaceae. This species is an important herb inoriental world medicine as used in treatment of so many diseases. In this work the essential oil content variation andantimicrobial activity have been determined. Fresh leaves of Th. Orientalis, grown in the south Syria were subjected tohydro distillation using a Clevenger-type apparatus and the chemical composition of the essential oil have been studiedusing gas chromatography-mass spectrometry (GC-MS). Mono and sesquiterpenoids in essential oil were reported as chemical constituents of this plant. Twenty-four components (97.59%) were identified. The major components were α-pinene(22.25%), 3-carene (20.65%), cedrol (18.71%), β –Caryophyllene (6.13%), α-Humulene (5.68%), Terpinolene (4.53%),and Limonene (3.35%). The present study led to investigate the antimicrobial activity of the essential oil against somepathogenic microorganisms. The essential oil showed appreciable antibacterial effect against some Gram-positive less thanGram negative bacteria. Minimum inhibitory concentration (MIC) revealed the lowest activity against Streptococcus pyogens and Vibrioparahaemplyticus (1.6 mg/mL) while the highest activity was against Bacillus subtilis and Staphylococcusaureus (0.4 mg/mL). The MBC activity was from (1.6 mg/mL) to (3.2 mg/mL).

Thuja Orientalis (L) (Platycladus orientalis) belongs to the family of Cupressaceae. This species is an important herb inoriental world medicine as used in treatment of so many diseases. In this work the essential oil content variation andantimicrobial activity have been determined. Fresh leaves of Th. Orientalis, grown in the south Syria were subjected tohydro distillation using a Clevenger-type apparatus and the chemical composition of the essential oil have been studiedusing gas chromatography-mass spectrometry (GC-MS). Mono and sesquiterpenoids in essential oil were reported as chemical constituents of this plant. Twenty-four components (97.59%) were identified. The major components were α-pinene(22.25%), 3-carene (20.65%), cedrol (18.71%), β –Caryophyllene (6.13%), α-Humulene (5.68%), Terpinolene (4.53%),and Limonene (3.35%). The present study led to investigate the antimicrobial activity of the essential oil against somepathogenic microorganisms. The essential oil showed appreciable antibacterial effect against some Gram-positive less thanGram negative bacteria. Minimum inhibitory concentration (MIC) revealed the lowest activity against Streptococcus pyogens and Vibrioparahaemplyticus (1.6 mg/mL) while the highest activity was against Bacillus subtilis and Staphylococcusaureus (0.4 mg/mL). The MBC activity was from (1.6 mg/mL) to (3.2 mg/mL).