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The thermal degradation of linalool-chemotype Cinnamomum osmophloeum leaf essential oil and the stability effect of microencapsulation of leaf essential oil with β-cyclodextrin were studied. After thermal degradation of linalool-chemotype leaf essential oil, degraded compounds including β-myrcene, cis -ocimene and trans -ocimene, were formed through the dehydroxylation of linalool; and ene cyclization also occurs to linalool and its dehydroxylated products to form the compounds such as limonene, terpinolene and α-terpinene. The optimal microencapsulation conditions of leaf essential oil microcapsules were at a leaf essential oil to the β-cyclodextrin ratio of 15:85 and with a solvent ratio (ethanol to water) of 1:5. The maximum yield of leaf essential oil microencapsulated with β-cyclodextrin was 96.5%. According to results from the accelerated dry-heat aging test, β-cyclodextrin was fairly stable at 105 °C, and microencapsulation with β-cyclodextrin can efficiently slow down the emission of linalool-chemotype C. osmophloeum leaf essential oil.

The essential oils from leaves of Taiwan's indigenous cinnamon (Cinnamomum osmophloeum ct. cinnamaldehyde) have similar constituents as compared to that from commercial bark cinnamons. This indigenous cinnamon has been proven to have excellent bioactivities. To understand whether this indigenous cinnamon contains a high level of the hepatotoxic compound, coumarin, as often seen in Cassia cinnamons, current research focused on determining the coumarin content in this indigenous cinnamon and screening the low-coumarin clones. The results demonstrated that the coumarin contents in all tested indigenous cinnamon clones were much lower than that found in Cassia cinnamons. In addition, this indigenous cinnamon contains about 80% (w/w) of cinnamaldehyde and 0.4-2.7% (w/w) of eugenol in its leaf essential oils. This combination could provide this indigenous cinnamon a better shelf life compared to that of regular commercial cinnamons. These results suggested that leaves of this indigenous cinnamon could be a potential resource for a safer cinnamon substitute.

The thermal stability of leaf essential oils from various Cinnamomum osmophloeum and their constituents was investigated for the first time. The results indicated that trans-cinnamaldehyde (Cin) content in eugenol-free essential oil from C. osmophloeum was affected by high temperatures. The retention of Cin (RC) decreased to 17.4% after the essential oil was incubated for 8 h at 100 °C. In contrast, essential oils containing eugenol showed greater thermal stability. Seven kinds of antioxidants were added to Cin to improve its thermal stability. Among them, eugenol endowed Cin with the best thermal stability. We also investigated the influence of various amounts of eugenol on the thermal stability of both essential oil and Cin. Both essential oil and Cin showed excellent thermal stability when 0.62 and 2.60% (v/v) eugenol were added. In short, the thermal stability of essential oil and Cin could be effectively improved by adding appropriate amounts of eugenol.

Cinnamomum osmophloeum ct. linalool is one of the chemotypes of the indigenous cinnamon in Taiwan. In this study, hydrodistillation was used for extracting the essential oils (EOs) of C. osmophloeum ct. linalool leaves collected from various plants and seasons, and GC-MS and GC-FID were used to examine variations and contents of the chemical composition in EOs. Moreover, the absolute configuration of the main constituent and its EO content were illustrated by GC-FID with a chiral column. In addition, we also investigated the effect of the extraction time (1, 2, 6, and 10 h) on the yield of EO and the contents of the main constituents. Results from this study revealed that the average EO yield of 12 plants was 3.7%, and linalool accounted for more than 90%. The linalool in the EO was proved to be pure S-(+)-linalool, and its content in the leaves ranged from 28.8 ± 0.3 to 35.1 ± 0.2 mg/g. Furthermore, there were no obvious differences in EO yield and S-(+)-linalool content from various plants and seasons. On the other hand, we also demonstrated that EO and S-(+)-linalool from C. osmophloeum ct. linalool leaves can be completely extracted out by 1 h of hydrodistillation.

Cryptomeria japonica D. Don, called 'sugi' in Japanese, is an abundant and renewable potential resource of valuable natural products that may serve as natural biocides in Taiwan. Hydrodistillation (HD) and steam distillation (SD) were used for extracting the essential oils from C. japonica leaves in this study. The chemical constituents of the two leaf essential oils were identified by GC/MS analysis, and their antitermitic activities were evaluated. The results from the antitermitic tests against Coptotermes formosanus Shiraki showed that the leaf essential oils extracted by HD and SD had excellent antitermitic activities, with LD(50) values of 1.57 and 1.72 mg/g after 7 d of testing, respectively. Comparison of the chemical composition of the two leaf essential oils revealed that oxygenated diterpenes (kaur-16-ene) and oxygenated sesquiterpenes (β-elemol) were the dominant constituents. In addition, 13 constituents isolated from the C. japonica leaf essential oils were tested individually against C. formosanus. Among these constituents, β-elemol and α-terpineol achieved 100% termite mortality at the dosage of 1 mg/g after 7 d of testing. These results demonstrated that both C. japonica leaf essential oils as well as β-elemol and α-terpineol possessed commendable antitermitic activity., (Copyright © 2012 Verlag Helvetica Chimica Acta AG, Zürich.)

The species differentiation between Chamaecyparis formosensis, C. obtusa var. formosana, and C. obtusa, based on the composition of the leaf essential oils, was studied. The characterization of the oils by GC-FID and GC/MS analyses showed remarkable differences between these three essential oils. Cluster analysis (CA) and principal-component analysis (PCA) distinguished three groups of essential oils. The C. formosensis oil was dominated by α-pinene while those isolated from C. obtusa var. formosana and C. obtusa were characterized by high levels of (-)-thujopsene and α-terpinyl acetate, respectively. Moreover, the phylogenetic relationships of the genus Chamaecyparis were in agreement with previous findings based on morphological and molecular evidence. In addition, the essential oils from C. obtusa var. formosana could be classified into three chemical types, according to their different characteristic main compounds (β-elemol, (-)-thujopsene, and cis-thujopsenal). The biochemical correlations between the major constituents of the Chamaecyparis species were examined and their relationship is discussed., (Copyright © 2011 Verlag Helvetica Chimica Acta AG, Zürich.)

Background: The current study investigates, for the first time, the mosquito larvicidal activities of leaf and twig essential oils from Clausena excavata Burm. f. and their individual constituents against Aedes aegypti L. and Aedes albopictus Skuse larvae. The yields of essential oils obtained from hydrodistillation were compared, and their constituents were determined by GC-MS analyses., Results: The LC(50) values of leaf and twig essential oils against fourth-instar larvae of Ae. aegypti and Ae. albopictus were 37.1-40.1 microg mL(-1) and 41.1-41.2 microg mL(-1) respectively. This study demonstrated that C. excavata leaf and twig essential oils possess mosquito larvicidal activity, inhibiting the growth of mosquito larvae for both species at a low concentration. In addition, results of larvicidal assays showed that the effective constituents in leaf and twig essential oils were limonene, gamma-terpinene, terpinolene, beta-myrcene, 3-carene and p-cymene. The LC(50) values of these constituents against both mosquito larvae were below 50 microg mL(-1). Among these effective constituents, limonene had the best mosquito larvicidal activity, with LC(50) of 19.4 microg mL(-1) and 15.0 microg mL(-1) against Ae. aegypti and Ae. albopictus larvae respectively., Conclusion: The findings suggested that the essential oils from Clausena excavata leaf and twig and their effective constituents may be explored as a potential natural larvicide., (2008 Society of Chemical Industry)

Eleven compounds from indigenous cinnamon (Cinnamomum osmophloeum) leaf essential oil were identified by GC-MS and the dominant constituent was trans-cinnamaldehyde (79.85%). The toxicity of leaf essential oil and trans-cinnamaldehyde were then determined to study their effectiveness in controlling the red imported fire ant, Solenopsis invicta Buren. The results of the toxicity tests indicated that both the indigenous cinnamon leaf essential oil and trans-cinnamaldehyde had an excellent inhibitory effect in controlling the red imported fire ant. The LT(50) values for both 2% leaf essential oil and 2% trans-cinnamaldehyde after open exposure were 105.0min and 32.2min; after close exposure were 18.5min and 21.2min, respectively.