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Abstract Cinnamomum osmophloeum ct. linalool is one chemotype of indigenous cinnamon in Taiwan. Its leaf essential oil (LEO) and main component S-(+)-linalool both possess great anxiolytic activities. The aim of this study was to establish ultrasound-assisted microextraction (UAME) for extracting LEO from C. osmophloeum ct. linalool. The absolute content of S-(+)-linalool and chemical composition of LEO were analyzed using GC-MS and GC-FID. To obtain the optimal conditions for UAME, four parameters (ultrasonic extraction duration, power of ultrasound, times of extraction, and leaf weight of extraction) were investigated according to the S-(+)-linalool content extracted. Results showed that the optimal condition was 10 mg of leaf extracted using n-hexane in an ultrasonicator with ultrasonic power of 80 W for 1 min. Furthermore, the absolute content of S-(+)-linalool obtained by UAME (28.3 ± 0.5 mg/g leaf) was comparable with that extracted by the 30-min hydrodistillation (HD) (26.9 ± 2.7 mg/g leaf). UAME was then employed to extract S-(+)-linalool from leaves at different stages of maturity (young, semi-mature, and mature). Results indicated that only mature leaf contains large amounts of S-(+)-linalool. Of note is that the LEO extracted by UAME contains coumarin, while that extracted by HD does not. Coumarin is an important ingredient in a number of cosmetic products due to its odor-fixing properties. With UAME, the leaf of C. osmophloeum ct. linalool has potential to be used as an aromatic material for further applications. In conclusion, UAME established in the present study provides a simple and rapid method for the determination of S-(+)-linalool and chemical composition of LEO from C. osmophloeum ct. linalool.

The antifungal activity of leaf oils from different provenances of Cinnamomum osmophloeum was evaluated against Phellinus noxius and their chemical polymorphism. C. osmophloeum leaf oils of 15 provenances and their relative contents were classified into eight chemotypes, namely cinnamaldehyde, cinnamaldehyde/linalool, linalool, cinnamaldehyde/cinnamyl acetate, linalool/camphor, camphor/bornyl acetate, 1,8-cineole/p-cymene, and mixed types according to GC-MS, CA, and PCA. It was found that leaf oils of both cinnamaldehyde and cinnamaldehyde/cinnamyl acetate types had excellent inhibitory effects against P. noxius, and their IC50 values were 119.5 and 154.1 µg/ml, respectively. Furthermore, trans-cinnamaldehyde possessed the strongest antifungal activity among the constituents against P. noxius, and its IC50 values were 116.0 µg/ml.

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 xanthine oxidase inhibitory activity and thermostability of Cinnamomum osmophloeum leaf oil microencapsulated with β-cyclodextrin were evaluated in this study. The yield of leaf oil microcapsules was 86.3% using the optimal reaction conditions at the leaf oil to β-cyclodextrin ratio of 15:85 and ethanol to water ratio ranging from 1:3 to 1:5. Based on the FTIR analysis, the characteristic absorption bands of major constituent, trans-cinnamaldehyde, were confirmed in the spectra of leaf oil microcapsules. According to the dry-heat aging test, β-cyclodextrin was thermostable under the high temperature conditions, and it was beneficial to reduce the emission of C. osmophloeum leaf oil. Leaf oil microcapsules exhibited high xanthine oxidase inhibitory activity, with an IC50 value of 83.3 µg/mL. It is concluded that the lifetime of C. osmophloeum leaf oil can be effectively improved by microencapsulation, and leaf oil microcapsules possess superior xanthine oxidase inhibitory activity.