Hui-Ting Chang

Bioactivity of selected plant essential oils against the yellow fever mosquito Aedes aegypti larvae.

The bioactivity of 14 essential oils from five plants has been studied using the brine shrimp lethality test and the Aedes aegypti larvicidal assay. All essential oils screened had LC50 values smaller than 200 microg/ml, showing significant lethality against brine shrimp. In addition, nine of the 14 essential oils tested showed toxicity against the fourth-instar A. aegypti larvae in 24 h (LC50<100 microg/ml). Of these, the leaf and bark essential oils of Cryptomeria japonica demonstrated high larvicidal activity, the most active being the leaf essential oil of C. japonica, with a LC50=37.6 microg/ml (LC90=71.9 microg/ml), followed by the bark essential oil of C. japonica also showing high activity against A. aegypti larvae, with a LC50=48.1 microg/ml (LC90=130.3 microg/ml). The results obtained from this study suggest that the leaf and bark essential oils of C. japonica are promising as larvicides against A. aegypti larvae and could be useful in the search for new natural larvicidal compounds.

Antifungal activity of essential oil and its constituents from Calocedrus macrolepis var. formosana Florin leaf against plant pathogenic fungi.

Resistance to conventional fungicides causes the poor disease control of agriculture. Natural products from plants have great potential as novel fungicide sources for controlling pathogenic fungi. In this study antipathogenic activity of the leaf essential oil and its constituents from Calocedrus macrolepis var. formosana Florin were evaluated in vitro against six plant pathogenic fungi. Chemical analysis of leaf oil by GC/MS allowed identification of alpha-pinene (44.2%), limonene (21.6%), beta-myrcene (8.9%), beta-caryophyllene (8.2%), caryophyllene oxide (2.4%), alpha-cadinol (1.6%), beta-pinene (1.2%), and T-muurolol (1.1%) as main components. Sesquiterpenoid components of the oil were more effective than monoterpenoid components of the oil. In particular, T-muurolol and alpha-cadinol strongly inhibited the growth of Rhizoctonia solani and Fusarium oxysporum, with the IC(50) values < 50 microg ml(-1). These compounds also efficiently inhibited the mycelial growths of Colletotrichum gloeosporioides, P. funerea, Ganoderma australe and F. solani. These results showed that T-muurolol and alpha-cadinol possess antifungal activities against a broad spectrum of tested plant pathogenic fungi and could be used as potential antifungal agents for the control of fungal diseases in plants.

Comparisons of the photostability of esterified wood

Abstract The light stability of wood panel treated with acetic anhydride, succinic anhydride, maleic anhydride, and phthalic anhydride was compared. Results from the solid state CP/MAS 13 C NMR analyses revealed that the esterification of holocelluloses occurred mainly at the C-6 position in the amorphous cellulose component. After lightfastness testing, the change in the color of wood treated with phthalic anhydride was greater than that subject to the other treatments. The color difference and yellowness index of acetylated wood after irradiation were significantly less than controls, indicating that acetylation inhibited the photoyellowing of wood. In addition, results obtained from diffuse reflectance UV-VIS spectral analyses clearly demonstrated that the amount of chromophores generated in wood treated with phthalic anhydride was more than that of the untreated control after photodegradation, and that the amount of chromophores on the irradiated acetylated wood surfaces was much less than that of the others. Acetylation reduced the formation of colored derivatives on the wood surfaces and consequently inhibited the photodiscoloration of wood.

Antitermitic and antifungal activities of essential oil of Calocedrus formosana leaf and its composition.

Calocedrus formosana Florin (Cupressaceae) is an endemic tree species in Taiwan; its timber is recognized for natural decay resistance. To examine the antitermitic and antifungal activities of leaf essential oil and its main constituents, C. formosana leaves were extracted and the essential oils analyzed by GC-MS. Bioactivity tests against the termite Coptotermes formosanus demonstrate that the LC50 value of leaf essential oil is 27.6 mg/g. Furthermore, exposure to T-muurolol caused 100% mortality at a dosage of 5 mg/g after 14 d. Leaf oil constituents displayed activity against four fungi, Lenzites betulina, Pycnoporus coccineus, Trametes versicolor, and Laetiporus sulphureus. Two compounds, α-cadinol and T-muurolol, exhibited the strongest antifungal activity. The LC50 values of α-cadinol against L. sulphureus, L. betulina, and T. versicolor are 9.9, 28.6, and 30.4 μ g/ml, respectively.

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.

Moisture excluding efficiency and dimensional stability of wood improved by acylation

The dimensional stability and moisture excluding efficiencies (MEEs) of wood after acetylation, butyrylation, and hexanoylation, were evaluated in this study. After three acylation treatments, an excellent antiswelling efficiency of modified wood specimens was obtained. All the equilibrium moisture contents of acylated wood at three relative humidities (RHs) (33% RH, 65% RH, and 93% RH) were significantly reduced, as compared to those of untreated wood in the same RH, and the MEEs of acylated wood were greatly improved. Acylated wood has consistent MEE at each of the different RHs. With the same percentage of substituted hydroxyl groups, the decreasing order of the MEE of modified wood was hexanoylation > butyrylation > acetylation. This indicates that the molecular volume or hydrophobic property of the substituted acyl groups also has the influence on the MEE of modified wood, in addition to the degree of substitution of the hydroxyl groups.

Correlation between softwood discoloration induced by accelerated lightfastness testing and by indoor exposure

The correlation between accelerated lightfastness testing and indoor exposure in softwood discoloration was evaluated. The discoloration of softwood exposed to indoor environments was simulated by using an accelerated lightfastness tester equipped with UVA-351 lamps. The trends of the discoloration of three species of softwood (western hemlock, China fir, Japanese cedar) in the accelerated lightfastness testing were similar to those in the indoor exposure test. Bathochromic effects occurred in the spectral reflectance curves of wood with increase in exposure time, and consequently, its color turned yellowish-red. Using the acceleration shift factor (ASF), we could obtain a correlation between accelerated lightfastness testing and indoor exposure. Results from the ASFs of three softwoods examined indicate that discoloration in the accelerated lightfastness test is 250 times more severe than that in the indoor exposure test.

Inhibition of the photodiscoloration of wood by butyrylation

Summary The lightfastness of butyrylated China fir (Cunninghamia lanceolata var. lanceolata) and maple (Acer sp.) was evaluated in this study, and its effectiveness was compared with that of acetylated specimens. The color fading in acetylated China fir and maple woods was reduced to half that of untreated specimens, after a 24-day UV lightfastness test. The effectiveness of butyrylation on photodiscoloration prevention in wood was even more pronounced than that with acetylation. With an 18.57% weight percent gain, butyrylation remarkably inhibited the discoloration of wood following UV irradiation. Based on infrared spectral analysis, the lignin of both untreated and butyrylated woods deteriorated after exposure to UV light, but the holocellulose in butyrylated wood was more resistant to the UV light. Furthermore, results obtained from diffuse reflectance UV-VIS spectral analysis elucidated that the absorption of irradiated butyrylated wood, in comparison with that of the irradiated but untreated specimens, was lower in both UV light and visible light regions. It also revealed that the inhibition of photodiscoloration of wood by butyrylation was caused mainly by a significant reduction of chromophoric derivatives, such as quinoid compounds, formed on the wood surface.

Improvements in dimensional stability and lightfastness of wood by butyrylation using microwave heating

Microwave heating was used as the heat source for butyrylation of wood with the aim of reducing the reaction time. The photostability and dimensional stability of butyrylated wood were also investigated in this study. Chemical changes of wood were confirmed by cross polarization/magic angle spin 13C-nuclear magnetic resonance and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) after butyrylation by microwave heating. Results from DRIFT with the Si-Carb sampling technique revealed that, using microwave heating, a higher degree of butyrylation of maple wood occurred in the middle of the specimen than on the outer surface. The increase in yellowness index of butyrylated wood treated with microwave heating was much less than that of untreated wood after the lightfastness test, indicating that photoyellowing of wood is effectively inhibited by butyrylation using microwave heating. The dimensional stability of wood was also improved after modification.

Effects of chemical modification reagents on acoustic properties of wood.

Summary The acoustic properties of several chemically modified Sitka spruce samples (Picea sitchensis Carr.) were evaluated in the longitudinal direction of wood specimens. Sitka spruce treated with glyoxal and carboxymethyl cellulose (CMC) displayed superior acoustic properties to those obtained by the other treatments. The acoustic converting efficiency (ACE) of the glyoxal-CMC treated Sitka spruce was 1.84 times of that of the untreated specimen and the specific dynamic Youngs modulus (E′/r) was retained without decrement after such treatment. Changes in the tanδ of Sitka spruce treated with glyoxal and different concentrations of 1,4-butanediol were opposite. With a low concentration of 1,4-butanediol (10%), the tanδ of the treated specimen decreased as a result of the formation of crosslinked cyclic structures. The potential presence of more alkyl hydroxyl groups in the Sitka spruce, after being treated with glyoxal and a high concentration of 1,4-butanediol (20%), resulted in the increment of tanδ and the decrement of ACE. The impairment of the acoustic properties of Sitka spruce was caused by the introduction of free chains with endwise carboxylic acid groups into cell walls after the succinic anhydride treatment. Slight improvement on the ACE of Sitka spruce was achieved by the reaction with acetic anhydride and the decrease in the tanδ was about 15%, which was attributed to the partial formation of crosslinked matrix. These results revealed the improvement of the acoustic properties of chemically modified wood that was probably achieved only by the formation of network structures between wood components and reagents.