Chemical composition of essential oils extracted from six Murraya species and their repellent activity against Tribolium castaneum

Murraya genus (family Rutaceae) has been widely used as local traditional medicines in East Asia. The chemical composition of essential oils extracted from six Murraya species and their repellent activity against Tribolium castaneum was investigated. From the samples of Murraya tetramera, Murraya euchrestifolia, Murraya koenigii, Murraya kwangsiensis, Murraya exotica, and Murraya alata, essential oils were obtained by hydrodistillation and their yields were various from 0.03 to 0.23%. All together 36 components were identified by GC–MS from the essential oils samples. The constituents with relatively higher contents included α-cedrene (4.22–21.82%), β-caryophyllene (8.15–27.73%), γ-elemene (4.38–12.65%), γ-selinene (3.80–21.09%), α-selinene (2.60–10.68%), α-zingiberene (2.08–12.68%), spathulenol (3.08–11.80%), caryophyllene oxide (1.58–10.59%), β-eudesmol (1.33–25.32%), etc. Moreover, eight compounds, which were recognized as significant components in the essential oils of M. tetramera, and M. kwangsiensis, were isolated and they were identified as α-terpinene, β-caryophyllene, α-caryophyllene, alloaromadendrene, spathulenol, β-eudesmol, camphene and caryophyllene oxide. The repellent activity against T. castaneum was tested for all the six samples of essential oils and eight isolated compounds. The testing samples exhibited a variety of repellent activity against T. castaneum. Among them, the essential oils of two species (M. tetramera and M. kwangsiensis) and three isolated compounds (alloaromadendrene, spathulenol and caryophyllene oxide) showed the fair repellent activity with relatively higher yields of contents. They might be considered as potential materials for the development of natural repellents for control of insects in stored products. Meanwhile, cluster analysis was performed using the collectives of data which were obtained in the process of the experiments. It was found that the characteristics of the repellent activity against T. castaneum could be related to the chemical composition of the essential oils. There were some interesting senses brought out as well. Such as, the repellent activity of the essential oils would not be depend on the contents of individual bioactive compound, and the existence of some compounds might affect the repellent activity of the essential oils.