天然糖甙类化合物^13C—NMR位移范围规律的计算机解析方法

本文从糖甙类化合物的数据特点出发,用较严格的数学推导总结出原则上适用于任何类型的~(13)C-NMR 图谱化学位移范围规律计算机自动解析的方法,并从多方面说明了该方法的研究及实现对实际的~(13)C-NMR 图谱解析工作的意义和重要作用。     

Fractionation of glycoside aroma precursors in neutral grapes. Hydrolysis and conversion by Saccharomyces cerevisiae

Glycoconjugated aroma precursors from neutral grape varieties were fractionated on 5 g C18 RP cartridge. Each of the seven fractions collected was divided in three parts: first part was hydrolysed with Pectinol in order to determine total aromatic heterosides, while the second part was treated with an active strain of the yeast Saccharomyces cerevisiae UCLM 325 and the third part with acetonic powder of the same yeast strain. The studied strain proved effective in the hydrolysis of the heterosides of nerol and geraniol, cis-8-hydroxy-linalool, 8-hydroxy-dihydro-linalool, some benzenoids and some norisoprenoids derivatives such as vomifoliol and 3-oxo-α-ionol. Only whole cells are able to convert geraniol to citronellol.     

Free and bound flavour components of Amazonian fruits: 3-glycosidically bound components of cupuacu

The total quantity (11.7 mg/kg of pulp) of aglycones released by enzymatic hydrolysis of the glycosidic extract indicates a significant aroma potential for cupuacu. Among the 47 aglycones identified, 24 are not present in the free volatile fraction, among them, 4-methylguaiacol, 4-propylguaiacol, 2,6-dimethyl-octa-1,7-dien-3,6-diol, 2,6-dimethyl-oct-7-en-1,6-diol, homovanillic acid, 2-methyl-but-3-en-1-ol and acetic acid. The quantitatively most important aglycones are 3-methyl-butan-1-ol, 2-phenylethanol, linalol, (Z)-2,6-dimethyl-octa-2,7-dien-1,6-diol, butan-1-ol and hexan-1-ol. The methylated alditol acetates analysis of monosaccharides released by acid hydrolysis of the heterosidic extract, indicates that glucose is involved in glucosidic and glycosidic structures. Moreover, rhamnopyranose and xylopyranose units, bound in the terminal position, suggest the presence of rutinosides and small amounts of primeverosides. Six glucosides, hexyl, benzyl, 2-phenylethyl, (R) and (S)-linalyl and geranyl β- -glucopyranosides, five rutinosides, benzyl, (R) and (S)-linalyl, -terpineyl and 2-phenylethyl rutinosides and 3-methyl-but-2-enyl vicianoside were identified by GC–EIMS after TFA derivatization of the crude heterosidic fraction. Moreover, four linalol oxides, octyl, 3-methyl-butyl β- -glucopyranosides and hexyl, octyl, two linalol oxides and 3-methyl-butyl rutinosides, have been tentatively identified from their TFA mass spectra. Some glucosides are probably substituted by malonyl and unidentified acyl residues.     

Evolution of the aroma composition of wines supplemented with grape flavour precursors from different varietals during accelerated wine ageing

The wines obtained by fermentation of a model medium supplemented with flavour precursors from different grape varieties (Muscat, Chardonnay, Grenache, Tempranillo, Merlot, Cabernet Sauvignon, Verdejo, and Syrah) were submitted to an accelerated ageing at 50 °C for 9 weeks simulating maturation in the bottle. The volatile compounds coming from grape flavour precursors were extracted by SPE and determined by GC–MS at the end of the alcoholic fermentation and after 1, 3, and 9 weeks of ageing. In general, the biggest changes were observed in the first week of accelerated ageing, most compounds showing a significant increase and a further steady decrease in their concentrations. Unexpectedly, Riesling acetal, 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), and trans-1-(2,3,6-trimethylphenyl)buta-1,3-diene (TPB) also followed this trend. However, vanillin derivatives, furan linalool oxides, 3-oxo-β-ionone, actinidols, 4-ethylphenol, and guaiacol showed a continuous increase during the ageing process. Syrah and Muscat were the most different varieties after fermentation and also at the end of the process. Differences between the rest of the varieties increased during the accelerated ageing, and, in most cases, differences were in accordance with those observed after acid and enzymatic hydrolysis of the grape precursor extracts.     

Preparation of Glycosyltriazenes

O‐Unprotected glycosyltriazenes are prepared for the first time by coupling of 1‐anthraquinone‐1‐diazonium hydrogensulfate with β‐glycopyranosylamines to afford 1‐ (anthraquinone‐1‐yl)‐3‐( β‐glycopyranosyl)triazenes 3a—h . Acetylation of compounds 3 furnished the O‐acetates 4a—g . The stability of triazenes 3 results from fixation of the NH proton in an intramolecular hydrogen bond to one of the anthraquinone carbonyl oxgen atoms. Treatment of triazenes 4 with tert‐butyl hypochlorite afforded acetoglycosyl chlorides 6 and 1‐azidoanthraquinone 7 . With acetic acid the triazene 4a formed tetra‐O‐acetyl‐D‐xylopyranose 9 together with 1‐ aminoanthraquinone 10 .     

Contribution of free and glycosidically-bound volatile compounds to the aroma of muscat “a petit grains” wines and effect of skin contact

Free and glycosidically-bound volatile compounds of must, skin and wine from Muscat “a petit grains” cultivated in Spain were determined, and the effect of different skin contact times on the aroma composition and sensory characteristics of wines was investigated. Must and wine had a large quantity of mono-terpenes, mainly linalool, geraniol, and nerol. The most abundant glycosylated fraction was the mono and poly-oxygenated terpenes, followed by benzene compounds and norisoprenoids. Must skin contact at 18 °C during 15 and 23 h produced an important increase in the free and bound varietal compounds, which suggests the use of glycosidic enzymes, together with skin maceration, to increase wine aroma. From a sensory standpoint, must skin contact was very positive, since it brought about an increase in the fresh and fruity characteristic of the wines, and they also had more body.     

Formation of damascenone derived from glycosidically bound precursors in green tea infusions

Damascenone is well-known for its potent flavour with an extremely low odour threshold. Several glycosidically bound precursors of damascenone have been isolated from several plants, but little is known about their occurrences in green tea infusions. In this work, three major glycosidic precursors of damascenone, 9-O-β-d-glucopyranosyl-megastigma-6,7-dien-3,5,9-triol (1a), 9-O-β-d-glucopyranosyl-3-hydroxy-7,8-didehydro-β-ionol (2a), and 3-O-β-d-glucopyranosyl-3-hydroxy-7,8-didehydro-β-ionol (2b) were isolated and identified in green tea infusions, and the stereochemistries at C-3 and C-9 positions of aglycone parts of the three glycosidic precursors were determined as (3S, 9R)-1a, (3R, 9R)-2a, and (3R, 9R)-2b, respectively. Compounds 1a, 2a, and 2b as well as 3-O-β-d-glucopyranosyl-megastigma-6,7-dien-3,5,9-triol (1b) were hydrolysed to form damascenone in a model system with strong acidic conditions (pH 2.0) and at high temperature (90 °C). In contrast to hydrolysis of 2a and 2b, more damascenone was transformed from 1a and 1b. Furthermore, the β-d-glucosyl moiety at the C-3 position gave a higher dehydration rate from megastigma-6,7-dien-3,5,9-triol to 3-hydroxy-7,8-didehydro-β-ionol than compound 1a carrying the sugar residue at C-9 position. Interestingly, the four glycosidic precursors of damascenone were not hydrolysed to give damascenone under slightly acidic conditions (pH 5.4 and 120 °C for 10 min), but they could be transformed to damascenone in the presence of green tea infusions even under the equal conditions.     

糖苷类香料前驱体研究进展

本文阐述了糖苷类化合物作为一类香料前驱体的基本原理、其天然存在形式和转化途径。指出了研究此类化合物的意义 ,介绍了国内外研究现状 ,提出了一些具有参考价值的研发趋势 ,展望了它在食品风味化学领域的广阔应用前景。     

Cycloaddition Reactions of 1,3‐Diaza‐2‐azoniaallene Salts and Glycals

The 1,3‐diaza‐2‐azoniaallene salt 3a reacts stereoselectively with glycals ( 5a—e ) to afford pyrano[2,3‐d]‐1,2,3‐ triazolium salts 6a—e . In contrast to other 1,3‐dipolar cycloadditions of glycals reported so far, the stereoselectivity of compounds 6 is not determined by the substituent on C‐3 of the glycal. Both cis ( 6a,b ) and trans ( 6d,e ) substitutions on C‐7 and C‐7a were found for bicyclic compounds 6 (crystal structure of 6a ). Under the influence of acid 6e opens the pyran ring to give the triazolium salt 9 . Addition of antimony pentachloride to a solution of the glycal 5e and the chlorotriazene 2a results in the formation of the pyranotriazene 12 containing two triazene units. In the presence of acid the pyranotriazene 6c reacts with alcohols to afford 2‐hydrazino glycosides 13a,b, 15 , which with zinc dust in acetic acid are reduced to 2‐amino glycosides 14a,b .     

Aroma potential of Albillo wines and effect of skin-contact treatment

Free and glycosidically-bound aroma compounds were analysed in Albillo grape must, skin and wines, and the effects of different skin-contact treatments on aroma composition and wine sensory characteristics were evaluated. Musts and wines contained large amounts of C₆ and benzene compounds. Must skin contact, at 18 °C for 15 and 23 h, prompted a considerable increase in free and bound varietal compounds. Therefore, this technique, and the use of glycosidases are two methods recommended as a means for enhancing wine aroma. Skin-contact treatment intensified the fresh and fruity properties that were scored positively by wine tasters.