Yoshito Ohtani

Antioxidative and antiradical activities of Eucalyptus camaldulensis leaf oils from Thailand

The leaf essential oils (six samples) from three clones of Eucalyptus camaldulensis Dehnh. were characterized by gas chromatography-mass spectrometry. Radical scavenging and antioxidant properties were investigated by the 1,1-diphenyl-2-picylhydrazyl (DPPH) assay and the β-carotene bleaching test. It was found that the whole essential oil and its fractions had significant antioxidant effects when they were tested by each method. In the DPPH assay, the E. camaldulensis leaf oils showed IC50 inhibitory concentrations in the range of 1.75–12.62 mg/ml. In the β-carotene bleaching test, the IC50 valued were in the range of 14.30–118.55 μg/ml.

Combination treatment of kenaf bast fiber for high viscosity pulp

The viscosity of kenaf bast fiber has been found to be highly sensitive and variable with different pulping methods; therefore, it is important to choose proper chemicals and conditions for pulping and bleaching of kenaf bast fiber. From several pulping experiments, a nonconventional pulping method with a combination of ammonium oxalate pretreatment followed by soda pulping at normal pressure and then acidic chlorite delignification was developed to obtain high-viscosity pulp (162 centipoise). The optimum level of alkali dosage of soda pulping for high-viscosity pulp was found to be 15% (on pulp as NaOH). Pulps showed linear relations between viscosity and xylose or glucose contents, but the combination pulping method gave extremely high pulp viscosity, beyond the relations. The highest viscosity pulp from kenaf bast fiber demonstrated a tear index about twofold and a folding endurance 6.2-fold higher than those of Manila hemp pulp with comparable tensile and burst indexes. The high-viscosity pulp could be used in the production of high-quality currency paper or longevity paper for special uses.

Biological performance of Eucalyptus camaldulensis leaf oils from Thailand against the subterranean termite Coptotermes formosanus Shiraki

The antitermitic activities of leaf oils and their constituents, taken from three clones of Eucalyptus camaldulensis Dehnh. in Thailand, against Coptotermes formosanus Shiraki were investigated in contact and noncontact tests. The termiticidal mechanism was also examined. Antitermitic tests demonstrated that E. camaldulensis leaf oils were both contact toxicants and fumigants to C. formosanus with LC50 values ranging between 12.68 and 17.50 mg/g by the contact method, and between 12.65 and 17.50 mg/petri dish (100 cm3) by the noncontact method. p-Cymene and γ-terpinene were primarily responsible for the contact toxicity and 1,8-cineole was responsible for fumigation. From the investigation of termiticidal mechanism, E. camaldulensis leaf oils exhibited the inhibition of acetylcholinesterase activity and showed the common symptoms of a neurotoxic mode of action against C. formosanus.

Influence of the chemical composition of kenaf bast and core on the alkaline pulping response

The bast and core of kenaf,Hibiscus cannabinus L., have markedly different chemical components and alkaline cooking responses. The bast had about double the hot-water extractives content and only about half the lignin content of the core. The core contained a large amount of hemicellulose, mostly composed of xylan. The lignin structures of bast and core were also quite different: The former had a significant abundance of syringyl structures. Evidence showed that the bast was much more easily delignified than the core. When the bast and core were cooked together in alkaline condition, the pulp yields at the same kappa number were higher than those of the individual pulpings of bast and core. The bast-core pulping gave a positive effect on the yield of bast pulp in the sodaanthraquinone and kraft pulpings. On the other hand, kenaf was abundant in the hot water extractives. These extractives consumed alkali during cooking to a relatively large extent but acted as a protector of hemicellulose and slightly increased the pulp yields.

Physicochemical properties and chemical compositions of Melaleuca leucadendron leaf oils taken from the plantations in Java, Indonesia

Melaleuca leucadendron Linn. leaf oils from Gunung Kidul, Gundih and Sukun, Java, Indonesia, at tree ages of 5, 10, and 15 years were analyzed to elucidate their qualities and chemical compositions. These oils gave yields from 0.61% to 1.59%. The samples from Gundih produced the highest yields (1.42–1.59%) compared to those from Gunung Kidul and Sukun. These oils were colorless with an odor typical of Melaleuca oils. The specific gravity of essential oils in this study ranged from 0.870 to 0.912. The samples from Gunung Kidul were the highest in specific gravity (0.905–0.912). The refractive index values of oil samples ranged from 1.468 to 1.470, optical rotation ranged from (−)2.47° to (−)0.98°, and ratio miscibility of oils in 70% ethanol ranged from 1:1 to 1:9.67. The organoleptic profiles and physicochemical properties of M. leucadendron Linn. leaf oils in this study were evaluated based on the Indonesian National Standard (SNI) 06-3954-2006 for standard quality of Melaleuca essential oils; only a few specific gravity values were below the standard. GC-MS spectrometry analysis indicated the presence of 26 compounds. Among them, 1,8-cineole (44.76–60.19%), α-terpineol (5.93–12.45%), d(+)-limonene (4.45–8.85%), and β-caryophyllene (3.78–7.64%) were the major components. Samples from each site tended to decrease in 1,8-cineole content and increase in β-caryophyllene content as plant age increased. α-Terpineol was highest at plant age 10 years, and d(+)-limonene varied according to plant site and age.

A New Method of Sample Preparation for Kenaf Bast Fiber Length Analysis with Automated Fiber Length Analyzer

Summary Kenaf bast fiber bundles alternate radially in layers accompanied by sieve elements and phloem parenchyma cells. Fiber bundles are about 20 % in the area of a cross section of kenaf bast. Four sample preparation methods for kenaf bast fiber length analysis with an automated fiber length analyzer were compared and a new sample preparation method including three steps was proven to be accurate. Fiber bundles were obtained by acidified sodium chlorite treatment and an additional ammonium oxalate treatment. Following a 1% sodium hydroxide treatment, fiber bundles were completely separated into single fibers with no damage. Fiber length values of this method were more accurate and reliable than other three sample preparation methods and manual measurement with optical microscope.

Selection of plant population of kenaf (Hibiscus cannabinus L.) as a papermaking raw material on arid hillside land in China

Agronomic properties (whole stalk yield, fiber length distribution, chemical composition) and whole stalk kraft pulp characteristics (total pulp yield, pulp fiber length distribution, pulp sheet strengths) were examined for kenaf (variety Zhehong 8310) at four plant populations, ranging from 135 000 to 405 000 plants/ha on arid hillside land at Anji, Zhejiang, China. For agronomic properties, the final whole stalk yield was higher as the plant population increased and as the altitude of the location on the slope decreased. Average fiber lengths of bast and core showed maxima at 225 000 plants/ha. Cellulose content increased as the plant population increased. For the kraft pulp characteristics of kenaf whole stalk, the total pulp yield was lower as the plant population increased, with the maximum difference about 1.3%. Sheet strengths and average fiber length attained maxima at around 225000–315000 plants/ha. The largest pulp strengths (breaking length, burst index, and folding endurance) were seen at a plant population of 225000 plants/ha, and the largest tear index was seen at a plant population of 315 000 plants/ha. When the agronomic properties and whole stalk kraft pulp characteristics were combined, a plant population between 225 000 and 315 000 plants/ha, which is a little higher than that of kenaf bast production for textiles, was selected as the optimum cultivated kenaf plant population for whole stalk kraft pulp and papermaking on arid hillside land in China.

The Bioactive Compounds and Antioxidant Activity of Food Products of Rhizophora stylosa Fruit (Coffee and Tea Mangrove)

The objective of this study is to investigate the bioactive compounds and antioxidant activity of coffee and tea mangrove (locally known in Indonesia) produced from the fruit of Rhizophora stylosa. Furthermore, three raw materials of coffee mangrove were also investigated to clarify their potencies. The crude extracts of five samples were subjected to antioxidant assay using DPPH. The results show that the extract of tea mangrove has the strongest activity; then, it was successfully fractionated using different polarity of solvents and yielded acetone and methanol fractions that had high antioxidant activity. The acetone fraction was purified and gave fractions A1, A2, A3, A4, A5, and A6, but only A2 and A3 indicated antioxidant activity and, therefore, they were subjected to further purification. Fractions A3 (caffeine) and A2 gave AS1 (N,N-dimethyl-L-alanine), AS2 (quercetin-3-O-galactopyranoside), AS3 (dodecanoic acid), and AS4 that had the similar 1H-NMR spectrometric results with AS2, while the methanol fraction did not exhibit clear peaks on the chromatogram by HPLC. Therefore, the precipitation method was conducted to purify this fraction, and the precipitate was analyzed by NMR spectra. The results from 1H and 13C NMR indicate that this fraction is a typical polymer of condensed tannins, containing procyanidin and prodelphinidin units.