Growth-inhibiting effects and chemical composition of essential oils extracted from Platycladus orientalis leaves and stems toward human intestinal bacteria

The growth-inhibiting activities of the essential oils extracted from Platycladus orientalis leaves and stems were examined against intestinal bacteria. The leaf oil exhibited a strong response against Clostridium difficile and C. perfringens at 5.0 mg/disc, but the stem oil showed no inhibitory activity against intestinal bacteria. The oils from P. orientalis leaves and stems were analyzed by GC-Mass spectroscopy. The main constituents of the essential oil in P. orientalis leaves: alpha-pinene (18.5%), cedrene (13.6%), alpha-cedrol (11.3%), beta-caryophyllene (10.2%), 3-carene (8.2%), and alpha-terpinyl acetate (5.1%), and in the stems: alpha-pinene (17.7%), 3-carene (16.3%), beta-caryophyllene (13.4%), beta-phellandrene (9.5%), beta-selinene (6.5%), and alpha-cedrol (6.1%). The cedrene isomers showed significant (33.1-34.7 mm) inhibitory effect against C. difficile and C. perfringens and moderate inhibitory effect against Escherichia coli at 2.0 mg/disc. The oil of P. orientalis leaves, in which cedrene isomers are the major component, could be used as a selective inhibitor against harmful bacteria.