Biomedical subjects

Yoji Hayasaka

Publications and source records attributed to Yoji Hayasaka.

8 recordsLinked to original sources

PubMed2005

Genetic determinants of volatile-thiol release by Saccharomyces cerevisiae during wine fermentation.

Volatile thiols, particularly 4-mercapto-4-methylpentan-2-one (4MMP), make an important contribution to the aroma of wine. During wine fermentation, Saccharomyces cerevisiae mediates the cleavage of a nonvolatile cysteinylated precursor in grape juice (Cys-4MMP) to release the volatile thiol 4MMP. Carbon-sulfur lyases are anticipated to be involved in this reaction. To establish the mechanism of 4MMP release and to develop strains that modulate its release, the effect of deleting genes encoding putative yeast carbon-sulfur lyases on the cleavage of Cys-4MMP was tested. The results led to the identification of four genes that influence the release of the volatile thiol 4MMP in a laboratory strain, indicating that the mechanism of release involves multiple genes. Deletion of the same genes from a homozygous derivative of the commercial wine yeast VL3 confirmed the importance of these genes in affecting 4MMP release. A strain deleted in a putative carbon-sulfur lyase gene, YAL012W, produced a second sulfur compound at significantly higher concentrations than those produced by the wild-type strain. Using mass spectrometry, this compound was identified as 2-methyltetrathiophen-3-one (MTHT), which was previously shown to contribute to wine aroma but was of unknown biosynthetic origin. The formation of MTHT in YAL012W deletion strains indicates a yeast biosynthetic origin of MTHT. The results demonstrate that the mechanism of synthesis of yeast-derived wine aroma components, even those present in small concentrations, can be investigated using genetic screens.

Fermentation↗

PubMed2004

Mass spectrometric evidence for the existence of oligomeric anthocyanins in grape skins.

The fractionation of a grape skin extract by multilayer countercurrent chromatography coupled with step gradient elution allowed the preparation of a fraction almost devoid of free anthocyanins. This fraction appeared to be almost exclusively polymeric, as judged by liquid chromatographic-mass spectrometric (LC-MS) analysis, color-bleaching tests with sulfur dioxide, and thiolysis. Electrospray mass spectrometric analysis indicated that the pigmented material in this fraction was chiefly composed of direct condensation products of anthocyanin extending up to trimers. With regard to their linkages, the anthocyanin units in the oligomers were possibly linked by either an A-type (by both carbon-carbon and ether bonds) or B-type (by carbon-carbon bond) linkage, like proanthocyanidins. The terminal anthocyanin unit of the oligomers is consistently in the flavylium form but the extension units are in the flavan form for the A-type oligomers and in the flavene form for the B-type oligomers. Although their linkages still need to be defined rigorously, this is the first mass spectrometric evidence confirming the existence of anthocyanin oligomers in the grape skin extract.

Anthocyanins↗

PubMed2004

Fractionation of grape anthocyanin classes using multilayer coil countercurrent chromatography with step gradient elution.

Grape anthocyanins from rosé wine pomace and grape skins were fractionated by multilayer coil countercurrent chromatography (MLCCC). Tert-butyl methyl ether/n-butanol/acetonitrile/water acidified with trifluoroacetic acid (2/2/x/5) was chosen as the solvent system because of its demonstrated efficiency in separating anthocyanins. A method combining MLCCC and step gradient elution has been developed. This method enabled the fractionation of anthocyanins as series of glucosides, and the corresponding acetylated, coumaroylated, and caffeoylated derivatives. The different anthocyanins were identified on the basis of their UV spectra, their elution time on reversed-phase HPLC as well as by mass spectrometry. A polar-colored fraction free of anthocyanin monomers and corresponding to the material remaining in the stationary phase after the completion of the gradient was recovered.

Anthocyanins↗

PubMed2003

Application of stir bar sorptive extraction for wine analysis.

Stir bar sorptive extraction (SBSE) coupled with gas chromatography/mass spectrometry (GC/MS) was used to analyse wine samples for three applications: flavour and compositional analysis; 2,4,6-trichloroanisole (TCA), a common off-aroma in wine; and agrochemicals. SBSE was found to be orders of magnitude more sensitive than modern conventional methodology, allowing for lower detection and quantitation levels, and improved confirmation of identity; SBSE often gave better signal to noise in scan mode than other methods in selective ion monitoring (SIM) mode. With the help of their characteristic mass spectra all agrochemicals could be identified unambiguously at concentrations of 10 microg L(-1) in wine and a further 100 constituents were detected in a Cabernet Sauvignon sample. Thus it is now possible to analyse complex samples such as wine by scan mode, with better confirmation of identity, and without sacrificing sensitivity, where previously SIM methodology had to be used.

Agrochemicals↗

PubMed2003

Characterization of proanthocyanidins in grape seeds using electrospray mass spectrometry.

Two proanthocyanidin (PA) fractions, one (Sdp3) with the mean degree of polymerization (mDP) of 3 and the other (Sdp9) with mDP of 9, were obtained from a Vitis vinifera cv. Shiraz grape seed extract. The PA fractions were directly analyzed by electrospray ionization mass spectrometry (ES-MS) and negative ion mass spectra were recorded. The mass spectrum of Sdp3 exhibited only singly charged ions corresponding to the molecular mass of PA with a degree of polymerization (DP) up to 9 (nonamers). In contrast, Sdp9 yielded rather complex mass spectra featuring ions with single [M - H](-), double [M - 2H](2-) and triple [M - 3H](3-) charge representing the molecular masses of PAs up to a DP of 28. In addition, the degree of galloylation per procyanidin (DG) was observed to be up to 5 (pentagallates) in Sdp3 and 8 (octagallates) in the Sdp9. This is the first evidence obtained by mass spectrometry for the distribution of grape seed PAs with such a high degree of polymerization and a broad diversity of galloylation. ES-MS data together with the complementary information provided by acid hydrolysis provides a detailed picture of the composition of grape seed PAs.

Anthocyanins↗

PubMed2003

Chemical and olfactory characterization of odorous compounds and their precursors in the parotoid gland secretion of the green tree frog, Litoria caerulea.

When stressed or challenged by a predator, the Australian green tree frog, Litoria caerulea, emits a characteristic nutty odor from its parotoid glands. This study identifies the source of the odor as the cyclic amide 2-pyrrolidone (2-PyrO). In addition, we demonstrate the presence of 2-PyrO's straight chain form, gamma-aminobutyric acid or GABA, in the frog's glandular secretion and propose an odorant-precursor relationship. What role both compounds play in the frog's defensive strategy remains unknown. Prolonged exposure to the odor is shown to result in adverse effects that may be attributed to a GABAergic mechanism. It is our hypothesis, however, that the odor acts as an aposematic signal, indicating the toxicity of the frog's nonvolatile secretion.

Animal Communication↗

PubMed2002

Screening for potential pigments derived from anthocyanins in red wine using nanoelectrospray tandem mass spectrometry.

Red wine extracts were screened for potential wine pigments derived from anthocyanins, using a combination of nanoelectrospray tandem mass spectrometry techniques. Fourteen aglycons were considered to be of anthocyanidin origin on the basis of their MS/MS spectra. The proposed structures of the aglycons were anthocyanidin C-4 substituted with vinyl linkage between C-4 and the hydroxy group at C-5. The anthocyanidin derivatives identified in the wine extracts were vinyl, vinylmethyl, vinylformic acid, 4-vinylphenol, 4-vinylguaiacol, and vinylcatechin adducts of malvidin as well as vinylformic acid and 4-vinylphenol adducts of peonidin and petunidin. The presence of vinyl alcohol, 4-vinylcatechol, and 4-vinylsyringol adducts of malvidin was also proposed.

Anthocyanins↗

PubMedDate not supplied

Purification of anthocyanins from species of Banksia and Acacia using high-voltage paper electrophoresis.

A new method has been developed for the isolation and rapid identification of anthocyanins from two floricultural crops based on the use of high-voltage paper electrophoresis with bisulphite buffer. Using this method, anthocyanin pigments were successfully purified as their negatively charged bisulphite-addition compounds from crude extracts of plant tissue. In conjunction with liquid chromatography-electrospray mass spectrometry, the method enabled the anthocyanins from the flowers of two Banksia species and the leaves of two Acacia species to be identified. The Banksia flowers contained both cyanidin and peonidin-based pigments, while the Acacia leaves contained cyanidin and delphinidin derivatives.

Acacia↗