Agonistic/antagonistic properties of lactones in food flavors on the sensory ion channels TRPV1 and TRPA1.

Flavor compounds provide aroma and sensations in the oral cavity. They are not present alone in the oral cavity, but rather in combination with several other food ingredients. This study aimed to clarify the relationship between the mixing of pungent flavor compounds and the response of pungent receptors, TRPV1 and TRPA1 channels. We focused on lactones that activate TRPV1 despite their presence in bland foods, such as dairy products and fruits, and analyzed their interaction with receptors using TRPV1- and TRPA1-expressing HEK293 cells. We found that γ-octalactone, γ-nonalactone, and δ-nonalactone activated TRPA1. When mixed with pungent components, some γ- and δ-lactones inhibited capsaicin-mediated TRPV1 responses, and δ-dodecalactone inhibited allyl isothiocyanate-mediated TRPA1 responses. Furthermore, the dose-response relationship of capsaicin and γ-nonalactone to TRPV1 suggests that γ-nonalactone acts as an agonist or antagonist of TRPV1, depending on its concentration. Conversely, γ-nonalactone and δ-dodecalactone were found to act only as agonists and antagonists, respectively, against TRPA1. These results suggest that lactones in foods may not only endow food with aroma, but also play a role in modulating food pungency by acting on TRPV1 and TRPA1. The dose-response relationships of a mixture of flavor compounds with TRPV1 and TRPA1 provide insights into the molecular physiological basis of pungency that may be the cornerstone for developing new spice mix recipes.

Application of integrative physiological approach to evaluate human physiological responses to the inhalation of essential oils of Japanese citrus fruits iyokan (Citrus iyo) and yuzu (Citrus junos).

This study investigated the effects of essential oil odors from Japanese citrus fruits, iyokan (Citrus iyo) and yuzu (Citrus junos), on human psychology and both the autonomic and central nervous systems. The inhalation of both essential oils significantly increased miosis rate and fingertip temperature and could induce parasympathetic dominance by suppressing sympathetic nerve activity. Oxyhemoglobin concentration in the prefrontal cortex increased after the inhalation of yuzu essential oil and decreased after the inhalation of iyokan essential oil. Subjectively, the inhalation of both essential oils reduced the feelings of fatigue and improved the feelings of refreshment, suggesting that the effect of autonomic nervous activity might involve in these psychological changes directly. Moreover, we observed that task performance improved after inhaling yuzu essential oil, which may be due to the increase in oxyhemoglobin concentration in the prefrontal cortex.

Potent Odorants of Characteristic Floral/Sweet Odor in Chinese Chrysanthemum Flower Tea Infusion.

An investigation using the aroma extract dilution analysis (AEDA) technique applied to the aroma concentrates prepared from the tea infusions of two different types of Chinese chrysanthemum flowers (flower buds, blooming flowers) revealed that 29 aroma peaks were detected in the aroma concentrates, and 17 compounds were newly identified or tentatively identified in the chrysanthemum flower tea. AEDA also revealed that the aroma peaks having high flavor dilution factors mainly consisted of a floral/sweet note in addition to metallic and phenol-like/spicy notes. Among them, four aroma peaks having a floral/sweet were identified as verbenone, ethyl 3-phenylpropanoate, propyl 3-phenylpropanoate, and ethyl cinnamate, and a semiquantitative analysis revealed that the flower buds were rich in these compounds. Furthermore, a chiral analysis revealed that (-)-verbenone existed in both flowers at a 3 times higher concentration than (+)-verbenone. Additionally, because the detection threshold of (-)-verbenone was lower than that of the (+)-verbenone, it is concluded that the (-)-isomer was a main contributor of the aroma peak of verbenone in the chrysanthemum flower tea.

Aroma compounds in Japanese sweet rice wine (Mirin) screened by aroma extract dilution analysis (AEDA).

Thirty-nine key aroma compounds were newly identified or tentatively identified in the aroma concentrate of Japanese sweet rice wine (Mirin) by an aroma extract dilution analysis technique based on the 68 detected peaks. Among them, 3-(methylthio)propanal, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, 3-methylbutanoic acid, 2-methylbutanoic acid, and 2-methoxy-4-vinylphenol were detected with the highest FD factors in this study.

Investigation of fluorinated (Meth)acrylate monomers and macromonomers suitable for a hydroxy-containing acrylate monomer in UV nanoimprinting.

We investigated reactive fluorinated (meth)acrylate monomers and macromonomers that caused segregation at the cured resin surface of a viscous hydroxy-containing monomer, glycerol 1,3-diglycerolate diacrylate (GDD), and decreased the demolding energy in ultraviolet (UV) nanoimprinting with spin-coated films under a condensable alternative chlorofluorocarbon gas atmosphere. The X-ray photoelectron spectroscopy and contact angle measurements used to determine the surface free energy suggested that a nonvolatile silicone-based methacrylate macromonomer with fluorinated alkyl groups segregated at the GDD-based cured resin surface and decreased the surface free energy, while fluorinated acrylate monomers hardly decreased the surface free energy because of their evaporation during the annealing of the spin-coated films. The average demolding energy of GDD-based cured resins with the macromonomer having fluorinated alkyl groups was smaller than that with the macromonomer having hydrocarbon alkyl groups. The fluorinated alkyl groups were responsible for decreasing the demolding energy rather than the polysiloxane main chains. We demonstrated that the GDD-based UV-curable resin with the fluorinated silicone-based macromonomer was suitable for step-and-repeat UV nanoimprinting with a bare silica mold, in addition to silica molds treated by chemical vapor surface modification with trifluoro-1,1,2,2-tetrahydropropyltrimethoxysilane (FAS3) and tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane (FAS13).

Identification and characterization of volatile components causing the characteristic flavor in miso (Japanese fermented soybean paste) and heat-processed miso products.

The aroma concentrates of two types of raw miso (traditional Japanese fermented soybean paste) were prepared by combining solid phase extraction (SPE) and solvent-assisted flavor evaporation (SAFE) techniques. The aroma extract dilution analysis (AEDA) applied to the volatile fraction revealed 39 odor-active peaks with FD factors between 4(1) and 4(8). Among the perceived odorants, 32 odorants were identified or tentatively identified from the 39 odor-active peaks, and the newly identified odorants for the miso were half of them. Furthermore, by comparison of the FD factors between the raw miso and heat-processed miso, it was found that one increasing odorant (methional) and three decreasing odorants (1-octen-3-one, (Z)-1,5-octadien-3-one, and trans-4,5-epoxy-(E)-2-decenal) contributed to the flavor change during the heat processing. This finding suggested that the flavor change in the raw miso during heat processing is attributed to relatively few odorant changes. In addition, it was assumed that the amino acids included in the miso have a significant influence on the remarkable disappearance of the three decreasing odorants.

Key aroma compounds in roasted in-shell peanuts.

An investigation by using an aroma extract dilution analysis (AEDA) of the aroma concentrates made from freshly roasted in-shell peanuts and stored peanuts revealed a total of 43 key aroma compounds, including 8 newly identified compounds in peanuts. Among them, 2-isobutyl-3-methoxypyrazine, exhibiting an earthy note, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone, exhibiting a caramel-like note, were detected with the highest flavor dilution (FD) factor of 4096 in the fresh peanuts, followed by 3,5-dimethyl-2-ethylpyrazine, exhibiting a nutty note, as having the next highest FD factor of 1024. A quantitative analysis of the key aroma compounds having high FD factors in the fresh peanuts and stored peanuts revealed that 2-methyl-3-furanthiol, 2-acetyl-1-pyrroline, 2-propionyl-1-pyrroline, and 3,5-dimethyl-2-vinylpyrazine significantly decreased during storage, while methyl 2-methyl-3-furyl disulfide, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, and 2-methoxy-4-vinylphenol significantly increased. The sensory experiments revealed that the fresh peanuts presented strong roasty/meaty, popcorn-like, and nutty notes, as well as moderate spicy/burnt and caramel-like notes, whereas the stored peanuts presented significantly weak roasty/meaty and popcorn-like notes and a significantly strong spicy/burnt note. Based on the comparative AEDAs, the quantitative analysis, and the sensory analysis, it was concluded that the freshly roasted peanut aroma comprised the significant contributions of 2-methyl-3-furanthiol exhibiting a roasty/meaty note, and of 2-acetyl-1-pyrroline and 2-propionyl-1-pyrroline exhibiting a popcorn-like note, and the lesser contribution of 2-methoxy-4-vinylphenol exhibiting a spicy/burnt note. In particular, 2-methyl-3-furanthiol, which was only detected in the freshly roasted peanut aroma concentrate, might be an essential component describing the freshness of the roasted peanut aroma by its diffusive roasty/meaty note.

Studies on the key aroma compounds in raw (unheated) and heated Japanese soy sauce.

An investigation using the aroma extract dilution analysis (AEDA) technique of the aroma concentrate from a raw Japanese soy sauce and the heated soy sauce revealed 40 key aroma compounds including 7 newly identified compounds. Among them, 5(or 2)-ethyl-4-hydroxy-2(or 5)-methyl-3(2H)-furanone and 3-hydroxy-4,5-dimethyl-2(5H)-furanone exhibited the highest flavor dilution (FD) factor of 2048, followed by 3-(methylthio)propanal, 4-ethyl-2-methoxyphenol, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone having FD factors from 128 to 512 in the raw soy sauce. Furthermore, comparative AEDAs, a quantitative analysis, and a sensory analysis demonstrated that whereas most of the key aroma compounds in the raw soy sauce were common in the heated soy sauce, some of the Strecker aldehydes and 4-vinylphenols contributed less to the raw soy sauce aroma. The model decarboxylation reactions of the phenolic acids during heating of the raw soy sauce revealed that although all reactions resulted in low yields, the hydroxycinnamic acid derivatives were much more reactive than the hydroxybenzoic acid derivatives due to the stable reaction intermediates. Besides the quantitative analyses of the soy sauces, the estimation of the reaction yields of the phenolic compounds in the heated soy sauce revealed that although only the 4-vinylphenols increased during heating of the raw soy sauce, they might not mainly be formed as decarboxylation products from the corresponding hydroxycinnamic acids but from the other proposed precursors, such as lignin, shakuchirin, and esters with arabinoxylan.

Comparison of key aroma compounds in five different types of Japanese soy sauces by aroma extract dilution analysis (AEDA).

An investigation by the aroma extract dilution analysis (AEDA) technique of the aroma concentrate from five different types of Japanese soy sauces, categorized according to Japan Agricultural Standards as Koikuchi Shoyu (KS), Usukuchi Shoyu (US), Tamari Shoyu (TS), Sai-Shikomi Shoyu (SSS), and Shiro Shoyu (SS), revealed 25 key aroma compounds. Among them, 3-ethyl-1,2-cyclopentanedione and 2'-aminoacetophenone were identified in the soy sauces for the first time. Whereas 3-(methylthio)propanal (methional) and 3-hydroxy-4,5-dimethyl-2(5H)-furanone (sotolon) were detected in all of the soy sauce aroma concentrates as having high flavor dilution (FD) factors, 4-ethyl-2-methoxyphenol was detected as having a high FD factor in only four of the soy sauces (KS, US, TS, and SSS). Furthermore, 5(or 2)-ethyl-4-hydroxy-2(or 5)-methyl-3(2H)-furanone (4-HEMF) and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (4-HDMF), which were thought to be the key odorants in KS, were detected in KS, US, TS, and SSS, but the FD factors widely varied among them. The sensory evaluations demonstrated that the aroma descriptions of a cooked potato-like note and a caramel-like/seasoning-like note were evaluated as high scores with no significant differences among the five soy sauces. On the other hand, a burnt/spicy note was evaluated as having high scores in KS, TS, and SSS, but it was evaluated as having a low score in SS. The comparative AEDA experiments and the auxiliary sensory experiments demonstrated that the five different types of Japanese soy sauces varied in their key aroma compounds and aroma characteristics, and the key aroma compounds in KS might not always be highly contributing in the other types of Japanese soy sauces.

Studies on the key aroma compounds in soy milk made from three different soybean cultivars.

An investigation by aroma extract dilution analysis (AEDA) of the aroma concentrate of soy milk made from a major Japanese soybean cultivar, Fukuyutaka (FK), revealed 20 key aroma compounds having flavor dilution (FD) factors of not less than 64. Among them, 2-isopropyl-3-methoxypyrazine, cis-4,5-epoxy-(E)-2-decenal, trans-4,5-epoxy-(E)-2-decenal, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, and 2'-aminoacetophenone were identified as the key aroma compounds in soy milk for the first time. (E,E)-2,4-Decadienal exhibiting a fatty note and trans-4,5-epoxy-(E)-2-decenal exhibiting a metallic/sweet note were detected as having the highest FD factors of 4096, followed by hexanal (green), (E)-2-nonenal (fatty), and (E,E)-2,4-nonadienal (fatty) having FD factors of 1024. Although all of these compounds might be generated from lipids, various aroma components, which were thought to be generated from amino acids, sugars, and ferulic acid, were detected having FD factors of 64-256. Investigation by comparative AEDA experiments of the soy milk aroma concentrates of two cultivars for soybean curd and soy milk, FK and Vinton81 (VT), and one cultivar for boiled beans, Miyagishirome (MY), revealed that most of the key aroma compounds were common to all of them, but 2-isopropyl-3-methoxypyrazine, exhibiting a pea-like/earthy note, was detected only in FK and VT. In addition, a sensory experiment revealed that the pea-like/earthy notes in FK and VT were significantly stronger than that in MY. These results demonstrated that a pea-like/earthy note contributed by 2-isopropyl-3-methoxypyrazine might be one of the essential characteristics to describe soy milk aromas.

Isolation and identification of the umami enhancing compounds in Japanese soy sauce.

To clarify the key compounds that account for the umami taste of soy sauce, a typical Japanese soy sauce, Koikuchi Shoyu, was separated by preparative chromatography, and the umami enhancing fractions were screened on the basis of an umami intensity of a 6.0 mM monosodium L-glutamate (MSG) solution. Liquid chromatography-time of flight mass spectrometry (LC-TOFMS), 1D/2D nuclear magnetic resonance spectroscopy (NMR) studies of the umami enhancing fractions led to the identification of N-(1-deoxy-D-fructos-1-yl)pyroglutamic acid (Fru-pGlu), N-(1-deoxy-D-fructos-1-yl)valine (Fru-Val), N-(1-deoxy-D-fructos-1-yl)methionine (Fru-Met), pyroglutamylglutamine (pGlu-Gln), and pyroglutamylglycine (pGlu-Gly). Although all the compounds identified were at sub-threshold concentrations in the soy sauce, a taste reconstitution experiment revealed that they contributed part of the umami taste of the soy sauce.

Ubiquitin chains in the Dsk2 UBL domain mediate Dsk2 stability and protein degradation in yeast.

Ubiquitin-like (UBL)-ubiquitin-associated (UBA) proteins, including Dsk2 and Rad23, act as delivery factors that target polyubiquitinated substrates to the proteasome. We report here that the Dsk2 UBL domain is ubiquitinated in yeast cells and that Dsk2 ubiquitination of the UBL domain is involved in Dsk2 stability, depending on the Dsk2 UBA domain. Also, Dsk2 lacking ubiquitin chains impaired ubiquitin-dependent protein degradation and decreased the interaction of Dsk2 with polyubiquitinated proteins in cells. Moreover, Dsk2 ubiquitination affected ability to restore the temperature-sensitive growth defect of dsk2Δ. These results indicate that ubiquitination in the UBL domain of Dsk2 has in vivo functions in the ubiquitin-proteasome pathway in yeast.

Gene systems network inferred from expression profiles in hepatocellular carcinogenesis by graphical Gaussian model.

Hepatocellular carcinoma (HCC) in a liver with advanced-stage chronic hepatitis C (CHC) is induced by hepatitis C virus, which chronically infects about 170 million people worldwide. To elucidate the associations between gene groups in hepatocellular carcinogenesis, we analyzed the profiles of the genes characteristically expressed in the CHC and HCC cell stages by a statistical method for inferring the network between gene systems based on the graphical Gaussian model. A systematic evaluation of the inferred network in terms of the biological knowledge revealed that the inferred network was strongly involved in the known gene-gene interactions with high significance (P < 10(-4)), and that the clusters characterized by different cancer-related responses were associated with those of the gene groups related to metabolic pathways and morphological events. Although some relationships in the network remain to be interpreted, the analyses revealed a snapshot of the orchestrated expression of cancer-related groups and some pathways related with metabolisms and morphological events in hepatocellular carcinogenesis, and thus provide possible clues on the disease mechanism and insights that address the gap between molecular and clinical assessments.

Molecular and sensory studies on the umami taste of Japanese green tea.

Aimed at defining the key drivers for the quality-determining umami taste of a high-grade powdered green tea, called mat-cha, a bioactivity-guided fractionation using solvent extraction, solvent precipitation, preparative chromatographic separations, and human psychophysical experiments was applied on freshly prepared mat-cha. Liquid chromatography-tandem mass spectrometry and one-/two-dimensional nuclear magnetic resonance studies on isolated fractions led to the identification of l-theanine, succinic acid, 3,4,5-trihydroxybenzoic acid (gallic acid), and (1R,2R,3R,5S)-5-carboxy-2,3,5-trihydroxycyclohexyl-3,4,5-trihydroxybenzoate (theogallin) as umami-enhancing compounds in the green tea beverage, and it can be shown by sensory studies that these compounds are able to raise the umami intensity of sodium l-glutamate proportionally.