Chun-Ya Lin

Insecticidal activities of leaf and twig essential oils from Clausena excavata against Aedes aegypti and Aedes albopictus larvae.

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.

Antifungal Activities and Chemical Composition of Wood and Leaf Essential Oils from Cunninghamia konishii

Abstract In this study antifungal activities of essential oils from wood and leaf and their constituents of Cunninghamia konishii against four wood decay fungi and six plant pathogenic fungi were investigated. GC and GC-MS analyses show that the major compounds of wood essential oil were cedrol and α-pinene, while those of leaf essential oil were α-pinene and p-cymene. Antifungal tests demonstrated the wood oil from C. konishii used against Trametes versicolor, Lenzites betulina, Laetiporus sulphureus, and Gloeophyllum trabeum and leaf oil from C. konishii used against L. sulphureus had strong antifungal activities. Moreover, wood oil used against Rhizoctonia solani, Fusarium solani, Pestalotiopsis funereal, and Ganoderma australe also had strong antifungal activities. Among the seven constituents of wood oil, cedrol displayed the best antifungal properties, indicating that it may be used as potential antifungal agents for the control of fungal diseases in plants.

Phytochemicals from Cunninghamia konishii Hayata Act as Antifungal Agents

The aims of the present study were to isolate and identify the antifungal compounds from the ethanolic extract of Cunninghamia konishii wood and to evaluate their antifungal activities against wood decay fungi. The results showed that the n-Hex soluble fraction of the ethanolic extract from C. konishii wood had an excellent inhibitory effect against Lenzites betulina, Trametes versicolor, Laetiporus sulphureus, and Gloeophyllum trabeum, with IC(50) values of 33, 46, 62, and 49 μg/mL, respectively. By following the bioactivity-guided fractionation procedure, four sesquiterpenes, T-cadinol, cedrol, T-muurolol, and (-)-epi-cedrol, and three diterpenes, 13-epi-manool, cis-abienol, and isoabienol, were identified from the active subfractions. Among the main constituents of the ethanolic extract from C. konishii, T-cadinol, cedrol, and T-muurolol efficiently inhibited the growth of four wood-rot fungi at the concentration of 100 μg/mL, with antifungal indices of 51.4-100.0%, 68.3-100.0%, and 39.5-100.0%, respectively. Results of this study show that the ethanolic extract of C. konishii wood may be considered as a potent source of T-cadinol, cedrol, and T-muurolol as new natural antifungal agents.

Methods for Thermal Stability Enhancement of Leaf Essential Oils and Their Main Constituents from Indigenous Cinnamon (Cinnamomum osmophloeum)

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.

Potential source of S-(+)-linalool from Cinnamomum osmophloeum ct. linalool leaf: essential oil profile and enantiomeric purity.

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.

Rapid differentiation of three Chamaecyparis species (Cupressaceae) grown in Taiwan using solid-phase microextraction-gas chromatography/mass spectrometry, cluster analysis, and principal component analysis.

Three Chamaecyparis species (C. formosensis, C. obtusa, and C. obtusa var. formosana) are difficult to distinguish by the naked eye. Therefore, from the chemotaxonomic point of view, it would be valuable to find a simple and rapid method to differentiate these three Chamaecyparis species. In this study, the chemical compositions of biogenic volatile organic compounds (BVOCs) from mature leaves were analyzed using solid-phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS). Then cluster analysis (CA) and principal component analysis (PCA) were conducted for the BVOC constituents to reveal the differences among these three species. Results from SPME-GC/MS showed that the compositions of BVOCs from the three species were distinctly different. Moreover, these species were clearly differentiated according to the results of CA and PCA. In conclusion, the findings of this study suggest that SPME-GC/MS coupled with CA and PCA is a feasible and rapid technique to differentiate Chamaecyparis species with similar morphological characteristics.

Repellency of essential oils of Cryptomeria japonica (Pinaceae) against adults of the mosquitoes Aedes aegypti and Aedes albopictus (Diptera:Culicidae).

The purpose of this study was to investigate the repellent activities of essential oils from Cryptomeria japonica (sugi) against adults of mosquitoes Aedes aegypti and Aedes albopictus . Comparison of essential oils from four different plant parts of C. japonica revealed that essential oil from its leaf exhibited the best repellent activity against mosquitoes. To understand the relationship between volatile organic compounds and repellent activity, the solid-phase microextraction (SPME) method was employed to analyze volatile organic compounds of leaf essential oil. The SPME fiber was coated with divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS). The major volatile organic compounds in the cage were 3-carene, alpha-terpinene, limonene, gamma-terpinene, and terpinolene at 0 min. Results demonstrated that (-)-terpinen-4-ol was the major volatile organic compound adsorbed by SPME fiber during repellent assays. Furthermore, the repellent activities of six compounds against adults of the mosquitoes were evaluated, and the results revealed that (-)-terpinen-4-ol exhibited the best repellent activity against A. aegypti and A. albopictus.

Profiling of volatile compounds of Phyllostachys pubescens shoots in Taiwan.

This study examined the influence of heating temperature and duration on volatile aromatic components of spring and winter Phyllostachys pubescens shoots using SPME. Results from GC-MS analyses revealed that the main constituents in both bamboo shoots at ambient temperature include methoxy-phenyl oxime, followed by n-hexanol and 3Z-hexenal, which gives a fresh green aroma. Comparing the different compounds, between spring and winter shoots, revealed that spring bamboo shoots at ambient temperature comprise 12.30% methyl salicylate, which provides protection against insect attack, and 9.71% epi-cedrol; while winter bamboo shoots comprise 17.00% 1-octen-3-ol, which produces a distinct mushroom aroma. After heating at 100 °C for 60 min, a marked increase in relative content of benzyl salicylate (43.30%) and a significant decrease in methyl salicylate content in spring bamboo shoots were observed; while the major compound in winter bamboo shoots was n-heneicosane (78.09%) and the content of specific 1-octen-3-ol significantly decreased.

Chemical Composition and Antitermitic Activity against Coptotermes formosanusShiraki of Cryptomeria japonica Leaf Essential Oil

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 LD50 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.

A Potential Low-Coumarin Cinnamon Substitute: Cinnamomum osmophloeum Leaves

The essential oils from leaves of Taiwans 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.