Synthesis, Odour Characteristics, and Antimicrobial Activity of Optically Active (Z)-7-Decen-4-olide and Its Derivatives.

Six optically active (Z)-7-decen-4-olide derivatives (1a-1f) were synthesized in 99% enantiomeric excess using diastereomeric resolution. The odour properties of the racemic and optically active 1a-1f were evaluated in terms of their orthonasal aromas. All of the stereoisomers had different odour characteristics and thresholds. Decen-4-olides (1a-1c) had a strong fruity note, whereas undecen-4-olide (1d and 1e) and dodecen-4-olide (1f) had a strong green note. For 7-alken-4-olides (1a, 1d, and 1f), the (R)-enantiomer had a lower odour threshold than the (S)-enantiomer. In contrast, no difference in the odour threshold was observed for the enantiomers of the 8-alken-4-olides (1b and 1e). Furthermore, the antimicrobial activity against Escherichia coli (E. coli; ATCC 25922) and Staphylococcus aureus (S. aureus; ATCC 29213) were investigated. Although the no differences in the antimicrobial activity of the stereoisomers was observed, 1d and 1e showed slight antimicrobial activity against E. coli, whereas only 1f showed antimicrobial activity against S. aureus. No antimicrobial activity was exhibited by (R)-1f, whereas (S)-1f exhibited strong antimicrobial activity.

Enzyme-assisted Extraction of Bioactive Phytochemicals from Japanese Peppermint (Mentha arvensis L. cv. 'Hokuto').

In this study, we provide a method for obtaining essential oil from Mentha arvensis L. in large quantities. Three types of polysaccharide-degrading enzymes were investigated, namely cellulase A "Amano" 3, cellulase T "Amano" 4, and hemicellulase "Amano" 90. The optimum extraction conditions were the combined use of 2 wt% cellulase T and 2 wt% hemicellulase 90, and 3 h of incubation. Enzymeassisted extraction increased the amount of the essential oil from 2.2 mL to 3.0 mL, compared with the amount extracted without an enzyme.

Conversion and Hydrothermal Decomposition of Major Components of Mint Essential Oil by Small-Scale Subcritical Water Treatment.

Thermal stabilities of four major components (l-menthol, l-menthone, piperitone, and l-menthyl acetate) of Japanese mint essential oil were evaluated via subcritical water treatment. To improve experimental throughput for measuring compound stabilities, a small-scale subcritical water treatment method using ampoule bottles was developed and employed. A mixture of the four major components was treated in subcritical water at 180-240 °C for 5-60 min, and then analyzed by gas chromatography. The results indicated that the order of thermal resistance, from strongest to weakest, was: l-menthyl acetate, l-menthol, piperitone, and l-menthone. In individual treatments of mint flavor components, subsequent conversions of l-menthyl acetate to l-menthol, l-menthol to l-menthone, l-menthone to piperitone, and piperitone to thymol were observed in individual treatments at 240 °C for 60 min. As the mass balance between piperitone and thymol was low, the hydrothermal decomposition of the components was considered to have occurred intensely during, or after the conversion. These results explained the degradation of mint essential oil components under subcritical water conditions and provided the basis for optimizing the extraction conditions of mint essential oils using subcritical water.

Preparation of Optically Active δ-Tri- and δ-Tetradecalactones by a Combination of Novozym 435-catalyzed Enantioselective Methanolysis and Amidation.

A combination of Novozym 435-catalyzed methanolysis and amidation using racemic N-methyl-5-acetoxytridecan- and tetradecanamides as a substrate proceeded in good enantioselectivity to afford the corresponding (R)-N-methyl-5-acetoxyalkanamides, (S)-N-methyl-5-hydroxyalkanamides, and (S)-N-cyclohexyl-5-hydroxyalkanamides. Both enantiomers of δ-tri- and δ-tetradecalactones were synthesized in over 90% enantiomeric excesses from the corresponding (R)- or (S)-alkanamides. Addition of cyclohexylamine to Novozym 435-catalyzed methanolysis shortened 24-hour reaction time to reach about 50% conversion. Enantiomers of optically active δ-tri- and δ-tetradecalactones had different odors and thresholds.

Combination of Novozym 435-catalyzed enantioselective hydrolysis and amidation for the preparation of optically active δ-hexadecalactone.

A new enzymatic method for synthesis of enantiomerically enriched δ-hexadecalactone (3) based on the enzymatic kinetic resolution of N-methyl-5-acetoxyhexadecanamide (1) is described. A combination of lipase-catalyzed hydrolysis and amidation improved enantioselectivity. Lipase-catalyzed amidation was also investigated. Detailed screening of solvents and additive amines was performed. The addition of cyclohexylamine to lipase-catalyzed hydrolysis afforded the best results to give both enantiomers of 3 with more than 90% enantiomeric excess.

Bioconversion of Birch Wood Hemicellulose Hydrolyzate to Xylitol.

A sugar solution containing 42.9 g l(-1) of xylose was prepared from the wood of Japanese white birch (Betula platyphylla var. japonica) by hydrolysis with 3 % sulfuric acid with a liquor-to-solid ratio of 4 (g g(-1)) at 120 °C for 1 h. During the acid hydrolysis, undesirable by-products were generated, such as acetic acid, furfural, and low-molecular-weight phenols, which inhibit bioconversion of xylose to xylitol. These inhibitors were successfully removed from the hydrolyzate by sorption onto a steam-activated charcoal followed by treatment with an anion exchange resin. Bioconversion of the detoxified hydrolyzate to xylitol by the yeast Candida magnoliae was investigated under the microaerobic conditions. The oxygen transfer rate (OTR) varied from 9.6 to 22.3 mmol O2 l(-1) h(-1). The best fermentative performance of C. magnoliae in the birch wood hydrolyzate (xylitol yield 0.74 g xylitol g xylose(-1); volumetric productivity 1.0 g l(-1) h(-1)) was obtained at the OTR of 12.6 mmol O2 l(-1) h(-1).

Preparation of optically pure δ-lactones using diastereomeric resolution with amino acid as resolving agent.

Synthesis of optically pure δ-lactones by diastereomeric resolution was investigated. Amino acid derivatives, which can be obtained at a relatively low cost, were used as resolving agents. Six optically pure δ-lactones were efficiently synthesized using Cbz-L-alanine without other expensive resolving agents. Both enantiomers of δ-lactone obtained had over 98% enantiomeric excesses. This diastereomeric resolution is very efficient for the preparation of optically pure δ-lactones.

Synthesis of hydroxycinnamoyl ß-D-xylopyranosides and evaluation of their antioxidant properties.

Various hydroxycinnamoyl ß-d-xylopyranosides were efficiently prepared from 2,3,4-tri-O-acetyl-α-d-xylopyranosyl bromide (TAXB) with amine by amine-promoted glycosylation. The resulted acetylated hydroxycinnamoyl ß-d-xylopyranosides with acetoxy groups at C-2, C-3, and C-4 were regioselectively deacetylated at C-4 position with Novozym 435. Antioxidant activities of free hydroxycinnamic acids and the respective ß-d-xylopyranosides were evaluated by DPPH radical scavenging activity as well as their inhibitory effect on autoxidation of bulk methyl linoleate. The radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) decreased in the order ferulic acid>caffeic acid≈caffeoyl ß-d-xylopyranosides≈sinapinic acid>sinapoyl ß-d-xylopyranosides≈feruloyl ß-d-xylopyranosides>p-coumaric acid>p-coumaroyl ß-d-xylopyranosides. In bulk methyl linoleate, the antioxidant activity order against autoxidation was almost consistent with the scavenging activity order. The results showed that caffeoyl ß-d-xylopyranosides and sinapoyl ß-d-xylopyranosides were as effective as free caffeic acid, sinapinic acid, and ferulic acid.

Synthesis of glycosyl ferulate derivatives by amine-promoted glycosylation with regioselective hydrolysis using Novozym 435 and evaluation of their antioxidant properties.

Various glycosyl ferulates were efficiently synthesized from 2,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide (TAGB) with amine by amine-promoted glycosylation without using heavy metal. The resulted acetylated glycosyl ferulates with acetoxyl groups at C-2, C-3 and C-4 were regioselectively deacetylated at C-4 and C-6 positions with Novozym 435. Antioxidant abilities of free ferulic acids and its synthetic glycosyl ferulates were evaluated by inhibitory effect on autoxidation of bulk methyl linoleate as well as their radical scavenging activity. The radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH·) decreased in the order ferulic acid>sinapinic acid ≈ glycosyl sinapinates ≈ glycosyl ferulates>p-coumaric acid>glycosyl p-coumarates. In bulk methyl linoleate, the antioxidant activity order against autoxidation was very consistent with the scavenging activity order. The results showed that glycosyl ferulates and sinapinates were effective as well as free carboxylic acid forms.

Acyclic monoterpenes in tree essential oils as a shrinking agent for waste-expanded polystyrene.

We examined the dissolution of polystyrene (PS) into acyclic monoterpenes present in tree essential oils, to develop an environmentally friendly shrinking agent for waste-expanded polystyrene (EPS). The dissolving powers of geranyl acetate, geranylacetone, and geranyl formate [221.8-241.2 g PS (100 g solvent)(-1)] compared favorably with that of (R)-limonene [181.7 g PS (100 g solvent)(-1)]. Their favorable dissolving powers for PS can be explained by their flexible linear structures, which may be more accessible to the inside of bulk PS compared with cyclic monoterpenes. These acyclic monoterpenes and PS were recovered almost quantitatively by simple steam distillation of the PS solution.