Comparative Analysis of Volatile Terpenoids Composition in Rosemary Leaves in Response to Ionizing Radiation

This study examined differential regulation of volatile terpenoids produced by rosemary (Rosmarinus officinalis L.) leaves in response to ionizing irradiation. Headspace volatile collection from rosemary leaves by solid-phase microextraction-gas chromatography-mass spectrometry analyses revealed that rosemary leaves biologically synthesized 26 species of volatile terpenoids and their relative ratio were changed after the exposure to γ-irradiation. Relative ratio of oxygenated monoterpenes such as borneol, (-)-verbenone, lemonol, and bornyl acetate (except for 1,8-cineol, linalool, chrysanthenone, camphor, and (+)-verbenone) and sesquiterpene hydrocarbons (i.e., caryophyllene-type) increased when the rosemary leaves were exposed to γ-ray in a dose-dependent manner. On the contrary, the change of the ratio of oxygenated sesquiterpenes such as caryophyllene oxide was negligible, and that of monoterpene hydrocarbons like α-pinene, camphene, myrcene, and limonene was down-regulated. These results indicate that γ-irradiation can modify chemical structures of volatile terpenes, and can, thus, be applied to reconstitute chemical constituents in aromatic plants.