Claude L. Bayonove

The aroma of grapes. I. Extraction and determination of free and glycosidically bound fractions of some grape aroma components

Abstract A method of extraction and determination of free and glycosidically bound terpenols and of benzyl and 2-phenylethyl alcohols is suggested. The extraction was carried out by adsorbing these compounds on a non-ionic resin, Amberlite XAD-2, and then elution with various selective solvents. Free forms were directly determined by gas chromatography; glycosidically bound forms were first enzymatically hydrolysed to release aglycones. This method was applied to a number of mature grape varieties. The levels of glycosidically bound terpenols and aromatic alcohols were always high, usually much higher than the free forms. The varieties can be classified in two groups: those rich in free and bounds forms which give aromatic wines (Muscat varieties and Gewurztraminer), and those which contain small amounts of these compounds and which give more neutral wines.

Sequential enzymic hydrolysis of potentially aromatic glycosides from grape

Abstract The mechanism of action of α- l -arabinofuranosidase, α- l -rhamnopyranosidase, and β- d -glucopyranosidase on p -nitrophenyl and grape monoterpenyl disaccharide-glycosides has been studied. First, the (1→6) linkage is cleaved by either α- l -arabinofuranosidase or α- l -rhamnosidase, and arabinose, rhamnose, and the corresponding monoterpenyl β- d -glucosides are released. Subsequently, liberation of monoterpenol takes place after action of β- d -glucosidase. The possible use of these glycosidases for the enhancement of the aroma of grape juice and derived beverages is emphasised.

Analytical methods for monoterpene glycosides in grape and wine. II. Qualitative and quantitative determination of monoterpene glycosides in grape.

Free and glycosidically bound terpenes of five Vitis vinifera grape cultivars (muscat of Alexandria, muscat of Frontignan, muscat of Hamburg, muscat Ottonel and Gewürztraminer) were investigated. The free and bound fractions were separated by selective retention on Amberlite XAD-2 resin. The glycosidic fractions were analysed by gas chromatography and gas chromatography-mass spectrometry using either enzymic hydrolysis and subsequent analysis of the released aglycones or trimethylsilyl (TMS) and trifluoroacetyl derivatives. The known monoterpenyl, benzyl and 2-phenylethyl beta-D-glucopyranosides, beta-rutinosides, 6-O-alpha-L-arabinofuranosyl-beta-D-glucopyranosides and 6-O-beta-D-apiofuranosyl-beta-D-glucopyranosides were determined. A number of other glycosides were detected and the structures of some of them, mainly apiosylglucosides and glucosides with aglycones in higher oxidation state than linalol, were tentatively identified using the mass spectra of their TMS and TFA derivatives and the results obtained from the analysis of their aglycones.

Analytical methods for monoterpene glycosides in grape and wine: I. XAD-2 extraction and gas chromatographic—mass spectrometric determination of synthetic glycosides☆

Synthetic monoterpene and aromatic beta-D-glucopyranosides, beta-rutinosides and 6-O-(alpha-L-arabinofuranosyl)-beta-D-glucopyranosides and their corresponding alcohols, diluted in a synthetic solution imitating wine, were isolated and separated by selective retention on Amberlite XAD-2. The corresponding recoveries and the conditions for the direct determination of these glycosides by gas chromatography and gas chromatography-mass spectrometry after derivatization were determined. Trifluoroacetylation gave the best results but trimethylsilylation provided complementary results. The separation of some diastereoisomeric monoterpene glycosides was also examined.

Purification and partial characterization of β-glucosidase from grape

Abstract β-Glucosidase was isolated from mature grapes (cv Muscat of Alexandria) and partially purified. The procedure used chromatography on Ultrogel AcA 44 and DEAE-Sepharose CL-6B. Two distinct peaks with β-glucosidase activity were reported. Except for their M r (98 000 for β-glucosidase 1, 50 000 for β-glucosidase 2) no differences occurred in other biochemical characteristics. For both, the optimum pH of activity was 5.0, the optimum pH for stability between 6 and 8, and the optimum temperature 45°. Their heat stabilities were also quite similar. The K m and V max values differ according the substrates. Affinity was maximal for p -nitrophenyl-β- d -glucoside. For natural substrates, the two enzymes had a high affinity for geranyl-β- d -glucoside. Glucose and gluconolactone were competitive inhibitors with K i of 170 and 0.215 mM respectively. Ca 2+ and Cu 2+ ions and p -chloromercuribenzoate also inhibited the enzymes.

Enzymatic synthesis of monoterpenyl β-D-glucosides by various β-glucosidases

Abstract β-glucosidases from Aspergillus niger, Trichoderma reesei, Candida molischiana , and almond have been shown to catalyze synthesis of β-glucosides of primary monoterpene alcohols, such as geraniol, nerol, and citronellol, using cellobiose as carbohydrate donor. Enzymes had the strongest glucosyl transferase activity for geraniol. Glucosylation of (±)-citronellol was nonselective. Among organic solvents tested, 30% acetone in enzyme assay gave the highest yield in glucoside synthesis. Monoterpene alcohols, such as linalool, α-terpineol, and menthol, were not used as acceptors in transglycosylation reactions.

Synthesis and n.m.r. spectral properties of grape monoterpenyl glycosides

Abstract Several grape 6-O-(6-deoxy-α- l -mannopyranosyl)-β- d -glucopyranosides and 6-O-α- l -arabinofuranosyl-β- d -glucopyranosides having (E)- and (Z)-3, 7-dimethyl-2, 6-octadien-1-yl, (R, S)-3, 7-dimethyl-1, 6-octadien-3-yl, (R, S)-1-methyl-1-(4-methyl-3-cyclohexen-1-yl)ethyl, benzyl, and 2-phenylethyl as aglycon group, as well as such diglycosides of chromogenic 4-nitrophenol, were synthesized by two methods, one involving mercuric cyanide-catalyzed glycosylation with glycosyl halides, and the other by acid-catalyzed glycosylation with glycosyl trichloracetimidates. Their 1H- and 13C-n.m.r. spectra, especially the glycosylation shifts of the 13C-signals, were investigated.

6-O-α-L-arabinopyranosyl-β-D-glucopyranosides as aroma precursors from passion fruit

Abstract The 6-O-α- l - Arabinopyranosyl -β- d - glucopyranosides of linalool, benzyl alcohol and 3-methyl-but-2-en-1-ol were isolated from passion fruit ( Passiflora edulis ) by adsorption chromatography on XAD-2 resin, then further extracted on the same resin after partial enzymic hydrolysis and semi-preparative chromatography on RP-18 phase by HPLC. Their structures were identified by 1 H NMR spectroscopy and mass spectral analysis and by methylation analysis of the carbohydrate moieties.

Multiple forms of glycosidases in an enzyme preparation from Aspergillus niger: Partial characterization of a β-apiosidase

Abstract Chromatofocusing on PBE 94 of a crude enzyme preparation from Aspergillus niger showed the presence of multiple forms of β-apiosidase, β-glucosidase, α-rhamnosidase, and α-arabinofuranosidase. A β-apiofuranosidase from the enzyme preparation was purified 27-fold by gel filtration and ion-exchange chromatography. The molecular mass of the enzyme and the Km value for p-nitrophenyl-β- d -apiofuranoside were 84,000 and 3.3 m m , respectively. The optimum pH and temperature for the enzyme activity were between pH 5.0–6.0 and 50–60°C, respectively. The enzyme was stable up to 50°C and between pH 4.0–7.0. Geranyl, linalyl apiosylglucosides, aroma precursors in grape, and a flavone apiosylglucoside were the substrates for the β-apiosidase.

Changes in free and bound fractions of aromatic components in vine leaves during development of muscat grapes

Abstract Some aroma components of the grape Vitis vinifera cv Muscat of Alexandria (free and glycosidically bound terpenols, benzyl and 2-phenyl ethyl alcohols) were studied in vine leaves during the period of development and maturation of the fruit. These components seem to be synthesized in the leaf blade. The leaf stalk was characterized by high levels of terpenols, particularly free ones such as geraniol and citronellol.