Regionality in Australian Pinot noir wines: A study on the use of NMR and ICP-MS on commercial wines.

Wine quality and character are defined in part by the terroir in which the grapes are grown. Metabolomic techniques, such as nuclear magnetic resonance (NMR) spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS), are used to characterise wines and to detect wine fraud in other countries but have not been extensively trialled in Australia. This paper describes the use of ICP-MS and NMR to characterise a selection of Pinot noir wines. Wines from varying terroirs could be somewhat distinguished by their mineral content using principal component analysis (PCA). PCA was able to separate wines by their Australian states more clearly than by region. Metabolomic analysis of the wines using NMR did not find any correlations with climate/daytime temperatures, or region. An analysis of coinertia suggested that the two datasets were not redundant, and it is proposed that ICP-MS data is the most useful for determining regionality.

Removal of Volatile Phenols From Wine Using Crosslinked Cyclodextrin Polymers.

Volatile phenols have been implicated as contributors to off-odors associated with taints from bushfire smoke and microbial spoilage. Various methods for the amelioration of off-odors have been evaluated, but to date, they have not included cyclodextrin (CD) polymers. In the current study, two CD polymers were prepared from ß- and γ-CD, using hexamethylene diisocyanate (HDI) as a crosslinking agent. Adsorption tests were performed with four volatile phenols (guaiacol, 4-methylguaiacol, 4-ethylguaiacol and 4-ethylphenol) at concentrations up to 1 mg/L. The removal of volatile phenols by CD polymers achieved equilibrium almost instantly, with isotherm tests suggesting an adsorption capacity of 20.7 µg of volatile phenol per gram of polymer. Langmuir and Freundlich models were subsequently used to fit the data. In batch adsorption tests, the CD polymers achieved 45 to 77% removal of volatile phenols. Polymer reusability was also evaluated and was found to be excellent. A comparison between volatile phenol adsorption by CDs vs. CD polymers, determined using a novel four-phase headspace solid-phase microextraction (HS-SPME) method for gas chromatography-mass spectrometry (GC-MS), suggests CD polymers offer several advantages for use by the wine industry.

Development and Evaluation of a HS-SPME GC-MS Method for Determining the Retention of Volatile Phenols by Cyclodextrin in Model Wine.

Volatile phenols exist in wine and can be markers for Brettanomyces and smoke taint off-odors. Cyclodextrins (CDs) are found to be capable of forming inclusion complexes with volatile phenols. Cross peaks on 2D 1H ROESY nuclear magnetic resonance (NMR) spectra demonstrated inclusion of volatile phenols in the ß-CD cavity, while difference tests confirmed this resulted in a perceptible reduction of their sensory impact. However, a conventional headspace solid phase microextraction (HS-SPME) method using an isotopically labelled normalizing standard failed to quantify the residual volatile phenols by gas chromatography-mass spectrometry (GC-MS) because of inclusion of the standard by the CDs. A new method involving an additional liquid phase was developed and validated for quantitation of volatile phenols in the presence of CDs. The retention of eight volatile phenols by α-, ß-, and γ-CD was subsequently studied.

Preparation of Magnetic Polymers for the Elimination of 3-Isobutyl-2-Methoxypyrazine from Wine.

3-Isobutyl-2-methoxypyrazine (IBMP), the most prevalent grape-derived methoxypyrazine, can contribute green bell pepper, vegetative and herbaceous aromas and flavours to wines. At elevated concentrations, this potent odorant may mask desirable fruity and floral aromas in wine and may be considered as a fault. A new remediation method for wines with elevated IBMP levels has been trialled using magnetic polymers, prepared in the same way as ordinary polymers but with the incorporation of iron oxide nanoparticles as magnetic substrates. Characterisation by Fourier transform-infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) showed no difference between thermally synthesised and microwave synthesised polymers. Magnetic polymers were found to have removed over 40% of the IBMP present in spiked model wine and white wine within ten minutes. The addition of magnetic nanoparticles and microwave-induced polymerisation did not affect the adsorption properties of the polymer in model wine and the polymer could be regenerated at least five times. Both Langmuir and Freundlich isotherms were found to fit the data for both types of polymer. However, attempts to produce imprinted polymers were not achieved, as they were found not to be differentiated from non-imprinted counterparts via adsorption tests.

Hydroxycinnamoyl Glucose and Tartrate Esters and Their Role in the Formation of Ethylphenols in Wine.

Synthesized p-coumaroyl and feruloyl l-tartrate esters were submitted to Brettanomyces bruxellensis strains AWRI 1499, AWRI 1608, and AWRI 1613 to assess their role as precursors to ethylphenols in wine. No evolution of ethylphenols was observed. Additionally, p-coumaroyl and feruloyl glucose were synthesized and submitted to B. bruxellensis AWRI 1499, which yielded both 4-ethylphenol and 4-ethylguaiacol. Unexpected chemical transformations of the hydroxycinnamoyl glucose esters during preparation were investigated to prevent these in subsequent synthetic attempts. Photoisomerization gave an isomeric mixture containing the trans-esters and undesired cis-esters, and acyl migration resulted in a mixture of the desired 1-O-ß-ester and two additional migrated forms, the 2-O-α- and 6-O-α-esters. Theoretical studies indicated that the photoisomerization was facilitated by deprotonation of the phenol, and acyl migration is favored during acidic, nonaqueous handling. Preliminary LC-MS/MS studies observed the migrated hydroxycinnamoyl glucose esters in wine and allowed for identification of feruloyl glucose in red wine for the first time.

Relationship between Menthiafolic Acid and Wine Lactone in Wine.

Menthiafolic acid (6-hydroxy-2,6-dimethylocta-2,7-dienoic acid, 2a) was quantified by GC-MS in 28 white wines, 4 Shiraz wines, and for the first time in 6 white grape juice samples. Menthiafolic acid was detected in all but one of the wine samples at concentrations ranging from 26 to 342 µg/L and in the juice samples from 16 to 236 µg/L. Various model fermentation experiments showed that some menthiafolic acid in wine could be generated from the grape-derived menthiafolic acid glucose ester (2b) during alcoholic and malolactic fermentation. Samples containing high concentrations of menthiafolic acid were also analyzed by enantioselective GC-MS and were shown to contain this compound in predominantly the (S)-configuration. Enantioselective analysis of wine lactone (1) in one of these samples, a four-year-old Chardonnay wine showed, for the first time, the presence of the 3R,3aR,7aS isomer of wine lactone (1b), which is the enantiomer of the form previously reported as the sole isomer present in young wine samples. The weakly odorous 3R,3aR,7aS 1b form comprised 69% of the total wine lactone in the sample. On the basis of the enantioselectivity of the hydrolytic conversion of menthiafolic acid to wine lactone at pH 3.0 determined previously and the relative proportions of (R)- and (S)-menthiafolic acid in the Chardonnay wine, the predicted ratio of wine lactone enantiomers that would be formed from hydrolysis at ambient temperature of the menthiafolic acid present in this wine was close to the ratio measured, which was consistent with menthiafolic acid being the major or sole precursor to wine lactone in this sample.

Shiraz wines made from grape berries (Vitis vinifera) delayed in ripening by plant growth regulator treatment have elevated rotundone concentrations and "pepper" flavor and aroma.

Preveraison treatment of Shiraz berries with either 1-naphthaleneacetic acid (NAA) or Ethrel delayed the onset of ripening and harvest. NAA was more effective than Ethrel, delaying harvest by 23 days, compared to 6 days for Ethrel. Sensory analysis of wines from NAA-treated fruit showed significant differences in 10 attributes, including higher "pepper" flavor and aroma compared to those of the control wines. A nontargeted analysis of headspace volatiles revealed modest differences between wines made from control and NAA- or Ethrel-treated berries. However, the concentration of rotundone, the metabolite responsible for the pepper character, was below the level of detection by solid phase microextraction-gas chromatography-mass spectrometry in control wines, low in Ethrel wines (2 ng/L), and much higher in NAA wines (29 ng/L). Thus, NAA, and to a lesser extent Ethrel, treatment of grapes during the preveraison period can delay ripening and enhance rotundone concentrations in Shiraz fruit, thereby enhancing wine "peppery" attributes.

Mechanistic studies on the autoxidation of α-guaiene: structural diversity of the sesquiterpenoid downstream products.

Two unstable hydroperoxides, 6b and 10a, and 13 downstream sesquiterpenoids have been isolated from the autoxidation mixture of the bicyclic sesquiterpene α-guaiene (1) on cellulose filter paper. One of the significant natural products isolated was rotundone (2), which is the only known impact odorant displaying a peppery aroma. Other products included corymbolone (4a) and its C-6 epimer 4b, the (2R)- and (2S)-rotundols (7a/b), and several hitherto unknown epimers of natural chabrolidione A, namely, 7-epi-chabrolidione A (3a) and 1,7-epi-chabrolidione A (3b). Two 4-hydroxyrotundones (8a/b) and a range of epoxides (9a/b and 5a/b) were also formed in significant amounts after autoxidation. Their structures were elucidated on the basis of spectroscopic data and X-ray crystallography, and a number of them were confirmed through total synthesis. The mechanisms of formation of the majority of the products may be accounted for by initial formation of the 2- and 4-hydroperoxyguaienes (6a/b and 10a/b) followed by various fragmentation or degradation pathways. Given that α-guaiene (1) is well known to exist in the essential oils of numerous plants, coupled with the fact that aerial oxidation to form this myriad of downstream oxidation products occurs readily at ambient temperature, suggests that many of them have been overlooked during previous isolation studies from natural sources.

Comparison of the formation of peppery and woody sesquiterpenes derived from α-guaiene and α-bulnesene under aerial oxidative conditions.

Deuterium-labeled guaiane derivatives and their precursors, namely, d5-2R-rotundol (11a), d5-2S-rotundol (11b), d5-bulnesone (14), d5-2R-bulnesol (16), d7-α-guaiene (10), and d7-α-bulnesene (15), were synthesized in good yields as GC-MS internal standards for comparing the behavior of α-guaiene (1) and α-bulnesene (5) under autoxidative conditions. It was found that approximately 99% of α-guaiene coated onto filter paper and exposed to air at ambient temperature was autoxidized after 48 h and up to 7% of rotundone (3) and 0.6% of rotundols (2a/b) were formed during this period. Autoxidation of α-bulnesene (5) was considerably slower, with approximately 80% remaining after 2 days and yielding less than 1.5% of α-bulnesone (7) and 0.3% and 0.9% of bulnesols 6a and 6b, respectively, after 5 days. The results indicate the feasibility of rapid changes of aroma profiles of herbs and other plant materials over time when exposed to air.

Chemical Changes in Grape Stem and Their Relationship to Stem Color throughout Berry Ripening in Vitis vinifera L. cv Shiraz.

Little attention has been paid to the color change or chemical compositional changes that occur in grape stems and how this correlates with the berry ripening process. Recently we have found that the change in grape peduncle color of Shiraz (Vitis vinifera) from green at veraison to predominantly brown at harvest occurs in parallel with berry ripening and as such may represent a new way of assisting in the prediction of grape maturity and harvest date. We have now investigated further the link between certain key chemical compositional changes that occur in the grape stem (peduncle and rachis) from veraison to harvest and how these attributes correlate with the observed color change in the vineyard. We report that peduncle moisture content has an excellent linear correlation with the color hue value and is negatively correlated in a strong fashion with the chlorophyll and carotenoid pigment ratio (Ca+b/Cx+c) within the peduncles. Significant differences in the moisture content, total chlorophylls (including chlorophyll a and b levels), total carotenoids, total phenolics, and the antioxidant capacity (DPPH) levels between the peduncles and rachises were found as they evolve from veraison to harvest. Finally, we have demonstrated for the first time that peduncle moisture content codevelops with the prototypical berry ripeness parameters (oBrix, pH, TA), which provides for the development of a new approach for viticulturists and winemakers to evaluate grape ripeness through peduncle moisture levels and therefore assist in harvest decision making.

Synthesis of guaia-4(5)-en-11-ol, guaia-5(6)-en-11-ol, aciphyllene, 1-epi-melicodenones C and E, and other guaiane-type sesquiterpenoids via the diastereoselective epoxidation of guaiol.

The diastereomeric ratio of epoxidation of the internally bridged carbon-carbon double bond of guaiol (1a) is strongly influenced by the combined effects of the types of remote protecting groups on the hydroxyisopropyl side chain, choice of solvent, and epoxidizing reagent. This observation has allowed us to devise concise stereoselective syntheses of a range of guaiane-type sesquiterpenoids via an epoxidation, ring-opening/elimination, and functionality manipulation sequence. Natural products guaia-4(5)-en-11-ol (2a), guaia-5(6)-en-11-ol (3), and aciphyllene (4a) and epimers of the recently isolated natural products, 1-epi-guaia-4(5)-en-11-ol (2b), 1-epi-aciphyllene (4b), and 1-epi-melicodenones C (5a) and E (6a), were synthesized in good yields in relatively few steps.

Production of the pepper aroma compound, (-)-rotundone, by aerial oxidation of α-guaiene.

The aroma link between pepper and wine has recently been elucidated to be due to the important aroma compound rotundone. To date, rotundone is the only known impact odorant with a peppery aroma. Although the concentration found in products of natural origin is small, the odor detection threshold is among the lowest of any natural product yet discovered. We report herein the identification of the first known precursor to rotundone, namely, α-guaiene, and that one mechanism of transformation is simple aerial oxidation.

Corymbolone.

The title compound, C15H24O2 [systematic name: (4S,4aR,6R,8aR)-4a-hy-droxy-4,8a-dimethyl-6-(prop-1-en-2-yl)octahydro-naphthalen-1(2H)-one], features two edge-shared six-membered rings with the hydroxyl and methyl substituents at this bridge being trans. One adopts a flattened chair conformation with the C atoms bearing the carbonyl and methyl substituents lying 0.5227 (16) and 0.6621 (15) Å, respectively, above and below the mean plane through the remaining four C atoms (r.m.s. deviation = 0.0145 Å). The second ring, bearing the prop-1-en-2-yl group, has a chair conformation. Supra-molecular helical chains along the b axis are found in the crystal packing, which are sustained by hy-droxy-carbonyl O-H⋯O hydrogen bonding.

2-[(3S,3aS,5R,8S,8aS)-3,8-Di-methyl-hexa-hydro-1H,4H-3a,8a-ep-oxy-azulen-5-yl]propan-2-ol.

Four independent mol-ecules (A-D) comprise the asymmetric unit of the title compound, C15H26O2, which differ only in the relative orientations of the terminal -C(Me)2OH groups [e.g. the range of Cmethyl-ene-Cmethine-Cquaternary-Ohy-droxy torsion angles is 52.7 (7)-57.1 (6)°, where the Cmethyl-ene atom is bound to an epoxide C atom]. The five-membered rings adopt envelope conformations, with the methyl-ene C atom adjacent to the methine C atom being the flap atom in each case. In each mol-ecule, the conformation of the seven-membered ring is a half-chair, with the Cmethyl-ene-Cmethine bond, flanked by methyl-ene C atoms, being the back of the chair. Supra-molecular helical chains along the b axis are found in the crystal packing, sustained by hy-droxy-epoxide O-H⋯O hydrogen bonding. Mol-ecules of A self-associate into a chain as do those of D. A third independent chain comprising B and C mol-ecules is also formed. The studied crystal is a pseudo-merohedral twin (minor component ca 21%).

Synthesis of allo- and epi-inositol via the NHC-catalyzed carbocyclization of carbohydrate-derived dialdehydes.

A synthesis of carbocyclic sugars from carbohydrate-derived dialdehydes using organocatalysis has been developed. Sorbitol, mannitol, and galactitol were converted via 1,6-tritylation, perbenzylation or permethylation, detritylation, and Swern oxidation into 2,3,4,5-tetra-O-alkyl-dialdoses that were cyclized via the benzoin reaction promoted by a triazolium carbene. Manno- and galacto-configured dialdehydes gave predominantly single inosose stereoisomers in up to 75% yield if the mixture was acetylated prior to isolation while the gluco-dialdehyde afforded a mixture of three stereoisomers in 61% overall yield. The inososes were stereospecifically reduced using sodium borohydride and then deprotected to give allo- and epi-inositol in good yield that confirmed the structural and stereochemical assignments.

Examination of the phenolic profile and antioxidant activity of the leaves of the Australian native plant Smilax glyciphylla.

Together with the sweet principle component glycyphyllin A (3), seven phenolic compounds including two new dihydrochalcone rhamnopyranosides, glycyphyllin B (1) and glycyphyllin C (2), and five known flavonoids, catechin (4), kaempferol-3-O-ß-D-glucopyranoside (5), quercetin-3-O-ß-D-glucopyranoside (6), kaempferol-3-O-ß-neohesperidoside (7), and 2R,3R-dihydrokaempferol-3-O-ß-D-glucopyranoside (8), have been isolated from the ethanolic extract of the leaves of Smilax glyciphylla for the first time. The structures of these compounds were characterized by spectroscopic methods including UV, MS, and 1D and 2D NMR. In vitro antioxidant capacity tests employing FRAP and DPPH assays indicated that 1, 4, and 6 exhibited potent antioxidant activity and are the key phenolics responsible for the antioxidant activity of the leaf extract of S. glyciphylla.

Pallidol hexa-acetate ethyl acetate monosolvate.

The entire mol-ecule of pallidol hexa-acetate {systematic name: (±)-(4bR,5R,9bR,10R)-5,10-bis-[4-(acet-yloxy)phen-yl]-4b,5,9b,10-tetra-hydro-indeno-[2,1-a]indene-1,3,6,8-tetrayl tetra-acetate} is completed by the application of twofold rotational symmetry in the title ethyl acetate solvate, C40H34O12·C4H8O2. The ethyl acetate mol-ecule was highly disordered and was treated with the SQUEEZE routine [Spek (2009 ▶). Acta Cryst. D65, 148-155]; the crystallographic data take into account the presence of the solvent. In pallidol hexa-acetate, the dihedral angle between the fused five-membered rings (r.m.s. deviation = 0.100 Å) is 54.73 (6)°, indicating a significant fold in the mol-ecule. Significant twists between residues are also evident as seen in the dihedral angle of 80.70 (5)° between the five-membered ring and the pendent benzene ring to which it is attached. Similarly, the acetate residues are twisted with respect to the benzene ring to which they are attached [C-O(carb-oxy)-C-C torsion angles = -70.24 (14), -114.43 (10) and -72.54 (13)°]. In the crystal, a three-dimensional architecture is sustained by C-H⋯O inter-actions which encompass channels in which the disordered ethyl acetate mol-ecules reside.

Sensing free sulfur dioxide in wine.

Sulfur dioxide (SO(2)) is important in the winemaking process as it aids in preventing microbial growth and the oxidation of wine. These processes and others consume the SO(2) over time, resulting in wines with little SO(2) protection. Furthermore, SO(2) and sulfiting agents are known to be allergens to many individuals and for that reason their levels need to be monitored and regulated in final wine products. Many of the current techniques for monitoring SO(2) in wine require the SO(2) to be separated from the wine prior to analysis. This investigation demonstrates a technique capable of measuring free sulfite concentrations in low volume liquid samples in white wine. This approach adapts a known colorimetric reaction to a suspended core optical fiber sensing platform, and exploits the interaction between guided light located within the fiber voids and a mixture of the wine sample and a colorimetric analyte. We have shown that this technique enables measurements to be made without dilution of the wine samples, thus paving the way towards real time in situ wine monitoring.

Rapid method for proline determination in grape juice and wine.

Proline is typically the most abundant amino acid present in grape juice and wine. The amount present is influenced by viticultural and winemaking factors and can be of diagnostic importance. A method for rapid routine quantitation of proline would therefore be of benefit for wine researchers and the industry in general. Colorimetric determination utilizing isatin as a derivatizing agent has previously been applied to plant extracts, biological fluids, and protein hydrolysates. In the current study, this method has been successfully adapted to grape juice and wine and proved to be sensitive to milligram per liter amounts of proline. At sugar concentrations above 60 g/L, interference from the isatin-proline reaction was observed, such that proline concentrations were considerably underestimated in grape juice and dessert wine. However, the method was robust for the analysis of fermentation samples and table wines. Results were within ±10% agreement with data generated from typical HPLC-based analyses. The isatin method is therefore considered suitable for the routine analysis required to support research into the utilization or release of proline by yeast during fermentation.

Ozonolysis of bicyclic 1,2-dioxines: initial scope and mechanistic insights.

The ozonolysis of bicyclic 1,2-dioxines was investigated using a variety of 1,4-disubstituted 1,2-dioxines along with a 1,3-dialkyl and steroidal example, with yields ranging from moderate to excellent. Two different pathways were observed upon reaction of the 1,4-disubstituted 1,2-dioxines with ozone; one pathway saw the "expected" results, that is, cleavage of the olefinic moiety with generation of 1,4-dicarbonyl 1,2-dioxines, while the other pathway revealed a previously unobserved rearrangement involving cleavage of the peroxide linkage along with loss of either CO or CO(2). Several unsymmetrical ozonolyses were also performed to further investigate the origins of this rearrangement, and initial mechanistic insights into the fragmentation pathways are discussed.