Chemical Composition and Antibacterial Activity of Essential Oils from Different Parts of Leonurus japonicus Houtt.

The herb and fruits of Leonurus japonicus Houtt., named Yimucao and Chongweizi, respectively, in Chinese, have been widely used in China as gynecological medicines. The components of the essential oils obtained by hydrodistillation were investigated by GC-MS. The antibacterial activity of the essential oils was determined by micro-dilution assay. The results showed large variations in the chemical composition and antibacterial activity of the oils. The oil of Yimucao showed antibacterial activity against various Gram-positive bacteria and consisted mainly of sesquiterpenes and diterpenes, with phytone, phytol, caryophyllene oxide and beta-caryophyllene being the most significant constituents, whereas the oil of Chongweizi, mainly made up of bornyl acetate and aliphatic hydrocarbons, was inactive in the antibacterial assay. Further study of the main compounds in Yimucao oil showed that beta-caryophyllene had wide-spectrum activity against Gram-positive bacteria.