Kokki Sakai

The Difference of Reactivity between Syringyl Lignin and Guaiacyl Lignin in Alkaline Systems

The difference of reactivity between syringyl lignin and guaiacyl lignin in alkaline systems were investigated by using syringyl and guaiacyl types of β-aryl ether lignin model compounds, softwood and hardwood dioxane lignins, and softwood and hardwood meals. In the lignin model study, β-aryl ether of syringyl lignin model was cleaved much faster than that of guaiacyl lignin model by soda and soda/anthraquinone treatment. The formation of coniferyl alcohol and sinapyl alcohol from guaiacyl lignin model and syringyl lignin model, respectively, was almost proportional to the cleavage of β-aryl ether under these conditions. Based on the model studies, coniferyl alcohol and sinapyl alcohol from isolated lignin and protolignin by soda and soda/anthraquinone treatments were determined in order to evaluate the extent of β-aryl ether cleavage in the terminal units of lignin. The results in both the dioxane lignins study and the wood meals study also indicate that β-aryl ether of syringyl lignin is cleaved much more easily than that of guaiacyl lignin and that there is no difference of reactivity of guaiacyl lignin in hardwood lignin and softwood lignin. This high reactivity of syringyl lignin may contribute the faster delignification rate of hardwood than softwood.

Biodegradable polyurethane materials from bark and starch. I. Highly resilient foams

Liquefaction of the bark of Acacia mearnsii (BK) and cornstarch (CS) was conducted by using a solvent mixture consisting of poly(propylene glycol) (PPG), glyc- erol, and sulfuric acid with a weight fraction of 94/5/1 at 150°C. Solubilities of BK and CS were about 80% after 60 min and 100% after 20 min in the same solvent, respec- tively. Highly elastic or highly resilient (HR) polyurethane foams (PUFs) suitable for car-seat cushions were prepared from the liquefied BK and CS without removing the insoluble residue from the liquefaction mixture. About 20% of the insoluble residue from BK contributed remarkably to the improvement of flame resistance of the result- ing PUFs. HR PUFs having better resilience properties were prepared using PPG of molecular weight around 4000, as compared with poly(ethylene glycol) having the same hydroxyl value. PUFs were synthesized from three BKs with different tannin contents, that is, BK0 (tannin: 0%), BK1 (tannin: 43%), and BK2 (tannin: 48.5%), to evaluate the effect of the tannin content on their performance of resilience. Both the resilience value and density of the PUFs increased with increasing BK content for all BK systems. BK2 was chosen to prepare PUFs in the further work. When CS replaced part of BK, the density and compressive strength of the PUFs decreased with an increasing cornstarch proportion, whereas the resilience value had its maximum value when the weight ratio of CS:BK was 1:1. The PUFs were, to some extent, biodegradable: The average weight loss of samples buried in soil for 6 months was 15.6 wt %.

Novel vitamin E derivative with 4-substituted resorcinol moiety has both antioxidant and tyrosinase inhibitory properties.

A novel vitamin E derivative, (6″-hydroxy-2″,5″,7″,8″-tetramethylchroman-2″-yl) methyl 3-(2′,4′-dihydroxyphenyl)propionate (TM4R), which has a chromanoxyl ring and 4-substituted resorcinol moieties, was synthesized; and its inhibitory effects on tyrosinase, antioxidant ability, and lightening effect of ultraviolet B (UVB)-induced hyperpigmentation were estimated. TM4R showed potent inhibitory activity on tyrosinase, which is the rate-limiting enzyme in melanogenesis. The scavenging activities of TM4R on 1,1-diphenyl-2-picrylhydrazyl and hydroxyl radicals were found to be nearly the same as those of α-tocopherol. Furthermore, an efficient lightening effect was observed following topical application of TM4R to UVB-stimulated hyperpigmented dorsal skin of brownish guinea pigs. These results suggest that TM4R may be a candidate for an efficient whitening agent, possibly by inhibiting tyrosinase activity and biological reactions caused by reactive oxygen species.

Analysis of lignin by pyrolysis-gas chromatography. I. Effect of inorganic substances on guaiacol-derivative yield from softwoods and their lignins

To obtain lignin-derived pyrolysis products in larger yields. Curie-point pyrolysis was performed on the softwood species Japanese red pine (Pinus densiflora Sieb. et Zucc.), Japanese cedar (cryptomeria japonica D. DON) and Japanese cypress ( Chamaecyparis obtusa Endl.), and their dioxane lignins treated with various inorganic substances, over the temperature range 358-764℃. The resulting guaiacol derivatives (guaiacol, 4-methyl-, 4-ethyl- and 4-vinylguaiacols, eugenol, vanillin, cis- and trans-isoeugenol, and acetovanillone) were determined by gas chromatography. The softwood samples sandwiched between two sheets of heat-resistant filter paper made of borosilicate glass fibers yielded from 1.56 to 1.64 times more guaiacol derivatives than unsandwiched samples. Sandwiching the dioxane lignins between heat-resistant papers also increased the guaiacol-derivative yield. by 13 to 27%. The sandwich-2 method developed in this study is widely applicable as a sample preparation method for increasing the yield of lignin-derived products on Curie-point pyrolysis. Gas chromalo8rqhy; glass fiber. borosilicate; guaiacol derivatives; lignin; pyrolysis, Curiepoint., softwoods.

Substrate-Specific Peroxidases in Woody Angiosperms and Gymnosperms Participate in Regulating the Dehydrogenative Polymerization of Syringyl and Guaiacyl Type Lignins

Substrate specificities of enzymes involved in monolignol biosynthesis are recognized to control differentiation of guaiacyl and syringyl lignin, but peroxidases are regarded to have rather less substrate specificity and their specificity related to lignification has not been fully elucidated. We have investigated the substrate specificity of peroxidases (EC1.11.1.7) in poplar (Populus alba L.) and Japanese cedar (Cryptomeria japonica D. Don) with respect to the dehydrogenative polymerization of monolignols. Peroxidases were fractionated into three groups, namely soluble peroxidases ionically bound peroxidases (IPO). and covalently bound peroxidases. Populus IPO was found to have the largest preference for sinapyl alcohol among all of peroxidases from both woody plant species, and only this peroxidase could produce the dehydrogenative polymer (DHP) from sinapyl alcohol. On the other hand. all peroxidases from both Cryptomeria and Populus easily produced the DHP from coniferyl alcohol. The results support that the participation of substrate-specific peroxidases is an important factor regulating the accumulation of syringyl and guaiacyl lignins in angiosperms and gymnosperms. Electrophoresis of IPO revealed the existence of syringyl-specific isoperoxidase only in Populus IPO.

Biodegradation of sugarcane bagasse with marine fungus Phlebia sp. MG-60

A marine fungus,Phlebia sp. MG-60, and three white-rot fungi were incubated with whole sugarcane bagasse (WSB). The residual lignin content and holocellulose content in the decayed WSB were determined, and based on their content delignification selection factors of the fungi were calculated. More than 50% of lignin in the WSB was degraded byPhlebia sp. MG-60, and less than 10% of the holocellulose was lost. The WSB was fractioned by sieving to separate long-fiber bagasse, shortfiber bagasse, and bagasse pith. WhenPhlebia sp. MG-60 was incubated with the three fractions, more efficient delignification activity on the bagasse pith was observed. As the most efficient utilization of bagasse, we predict that bagasse fiber might be employed as the raw material in the pulp and paper industry after biopulping withPhlebia sp. MG-60 and bagasse pith, or WSB might be used to produce animal feed after fermentation with the strain.

A geranylated chalcone with 5α-reductase inhibitory properties from Artocarpus incisus

A geranylated chalcone was isolated from leaves of Artocarpus incisus and it showed potent 5alpha-reductase inhibitory activity.

Biological activity of extracts from Cupressus lusitanica cell culture

Ethyl acetate extracts ofCupressus lusitanica suspension cell cultures were examined for their biological activities (viz., tyrosinase inhibitory, antioxidant, and antimicrobial activities). The extract from elicitor-treated cells showed all of the biological activities, whereas the extract from cultures without elicitor was not bioactive to a discernible extent. The biological activities shown by the cell culture extracts were almost solely accounted for byβ-thuj aplicin contained in the extracts. These results suggest that the ethyl acetate extract ofC. lusitanica cells treated with the elicitor is a valuable bioactive source without isolation or purification ofβ-thujaplicin.

Studies on hypersaline-tolerant white-rot fungi L: screening of lignin-degrading fungi in hypersaline conditions

To search for marine fungi that have significant lignin-degrading ability in a hypersaline environment, eight strains of marine fungi were selected from 28 strains isolated from mushrooms and driftwood sampled from mangrove stands in Okinawa, Japan. We evaluated the decolorization ability, delignification ability, and biobleaching properties of the strains; then strain MG-60 was screened as a hypersaline-tolerant lignin-degrading fungus. We have summarized its growth, decolorization ability, and biobleaching properties at various sea salt concentrations. The strain has been estimated to belong to thePhlebia family.

Novel stilbenoids isolated from the heartwood of Shorea laeviforia

Abstract Two novel stilbenoids, laevifonol (an ε-viniferin-ascorbic acid hybrid compound) and laevifoside (an O-glucoside of ampelopsin A) were isolated from the heartwood of Shorea laeviforia. Their structures were elucidated by nuclear magnetic resonance spectroscopic evidence including HMQC, HMBC, and NOESY. The novel compounds and other known stilbenoids from S. laeviforia were evaluated for inhibitory activity against rat liver 5α-reductase. Positive inhibitory activities were observed in resveratrol dimers and tetramers. No inhibitory activity was detected in laevifonol and ampelopsin A glucosides, laevifoside, or hemsleyanoside, whereas inhibitory activity was seen in their aglycon. These results suggest that the hydrophilic moiety in these compounds may inhibit action with the hydrophobic active site of the enzyme.