In spoken language, the ” Thujene ” often refers to α-Thujene (occasionally called “Yabai Xi” in Chinese context). Its double bond isomers are β-Thujene and Cedrene. They are bicyclic monoterpenoids, a class of volatile organic compounds. The biological sources of “Thujene” can come from the various plant oil. In China, they are often extracted from the Sichuan pepper oil (Zanthoxylum Schinifolium Sieb.et Zucc. or Zanthoxylum Bungeanum Maxim), Vine pepper oil (Zanthoxylum armatum DC.), Eucalyptus extracts, Fleabane extracts, Galbanum oil, and other plants. Overseas, they are commonly found in North American Arborvitae (Thuja plicata D. Don), Black Seed (Nigella Sativa) and Summer Savory. The standard specifications of commercially available “Thujene” in industrial production are typically prepared using steam distillation or organic solvent extraction. For pharmaceutical-grade applications, more expensive processes such as molecular distillation (MD) or short path distillation (SPD) are used for preparation. The Thujene supplied by Foreverest® mainly comes from various plants. α-Thujene, β-Thujene, and Cedrene can be extracted as by-products during the process of preparing Limonene, Linalool, 1,8-Cineole, α-Pinene, β-Pinene, and 3-Carene.
α-Thujene and β-Thujene are present in relatively high concentrations in the essential oils of some plants, such as Sichuan pepper, Vine pepper, or North American Arborvitae1, and are considered important volatile compounds for providing woody aromas in sensory perception. They are considered important volatile compounds that provide a woody sense2. Researchers in China have analyzed the characteristic flavor of vine pepper oils and found that samples with a higher relative concentration of β-Thujene have a more pronounced woody flavor, similar to that of crushed wood chips. In the comparative analysis of volatile components in Sichuan Zuye pepper fruit, Thujene has an average relative content of 13.01% in different species of Zuye pepper fruit. Its relative content ranks third in the proportion of volatiles and, together with linalool (with an average relative content of 31.27%) and limonene (with an average relative content of 15.53%), serves as an important flavor source of Sichuan Zuye pepper fruit3. Among them, linalool provides a multi-layered flavor of strong green sweetness and spiciness to the pepper, limonene brings fresh fruity flavor, while Thujene provides woody sense.
In addition to traditional fragrance applications, β-Thujene has begun to be explored in the application of pheromones for pest control. In a study on the volatile substances of Huashan pine cones, researcher found that the quantity of volatile components did not change after the cones were damaged by Pine cone borer, but the concentration increased significantly4. The oviposition inhibitors or attractants in comparison to Pinus tabuliformis Carr. may be the main reason for the lack of oviposition by the Pine cone borer. After the damage to Huashan pine cones, the relative content of α- Thujene (3-Thujene) increased by 186.36% (from 0.22% to 0.41%), and the relative content of humulene (4-Thujene) increased by 218.8% (from 5.53% to 12.1%)4. This provides a development direction for the application of pheromones in pest control.
In the study on the prevention and control of adult Semanotus bifasciatus, it was found that Semanotus bifasciatus in the forest prefers to infest weakened Platycladus orientalis. By comparing the volatiles from healthy and weakened Platycladus orientalis, it was discovered that the relative content of α-Thujene and β-Pinene detected in the bark of weakened Platycladus orientalis was significantly higher than that in the wood, indicating that these two substances are likely signal molecules for the decline of Platycladus orientalis and may play an important role in the host selection process of Semanotus bifasciatus5. After being attacked by insects, the bark of trees is prone to peeling off. Weakened Platycladus orientalis are more likely to wither and die after insect infestations. In traditional pest control methods, chemical control methods use methyl bromide, sulfuryl fluoride, or 56% aluminum phosphide tablets for fumigation treatment. This method causes more serious pollution. Using bait trees for pest control can achieve a certain effect, but if the bait trees are not dealt with in a timely manner, the bait collection zone can easily become a breeding ground for pests, leading to artificial spread and harm.
The researchers found that a mixture containing Isoterpinolene, α-Pinene, Caryophyllene, and Limonene, or a mixture of Isoterpinolene, γ-Terpinene, 3-Carene, α-Pinene, α-Cedrene and Caryophyllene worked best as an attractant for the Semanotus bifasciatus. Due to the hidden lifestyle of the Semanotus bifasciatus, after the adults emerge, they can use volatile compounds released by host plants to locate suitable hosts. Bio-based attractants can be used to monitor and control this pest instead of using bait trees. In the future, plant-based pest control products are expected to replace traditional chemical treatments and logging methods, using more environmentally friendly methods to achieve economic benefits.
- Chen You-di, Comparative Study on Chemical Constituents of Essential Oils from Several Parts of Platycladus Orientalis, Chemistry and Industry of Forest Products, 1984.
- Xiao Zuobing, Analysis of Flavor Substances in Chrysanthemum Essential Oils, Journal of Chinese Institute of Food Science and Technology, 2018.
- WANG Lihua, Comparative analysis of fruit volatile components based on less and plenty prickle strains of Zanthoxylum armatum DC., Non-Wood Forest Research, 2021.
- LI Xin-gang, Volatile Terpene Composition in Cones of Pinus armandi, Acta Botanica Boreali-Occidentalia Sinica, 2005.
- Sun Yueqin, Sensilla and Behavioral Responses of adults of Semanotus bifasciatus (Coleoptera: Cerambycidae) to Volatile Compounds of Platycladus orientalis, P63, 2008.