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1.
The enantiomeric compositions of the acetates, butanoates, hexanoates, and octanoates of the secondary alcohols 2-pentanol, 2-heptanol, and 2-nonanol were determined in yellow (Passiflora edulis f. flavicarpa) and purple (Passiflora edulis Sims) passion fruits. The compounds were isolated by means of simultaneous distillation-extraction. Enantiodifferentiation was performed via multidimensional gas chromatography using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin as chiral stationary phase. The series of homologous 2-alkyl esters, which are typical constituents of purple passion fruits, were shown to be present as nearly optically pure (R)-enantiomers. The proportions of the (S)-enantiomers varied in different batches and were dependent on the alcohol moieties of the esters. For minor amounts of esters detected in yellow fruits, the (R)-enantiomers were also dominating. However, the enantiomeric excesses were significantly lower than in the purple variety. Enantioselective analysis of the free alcohols revealed that 2-heptanol exhibited opposite configurations in purple and yellow passion fruits. A similar phenomenon was observed for 2-pentanol, which was present in the yellow fruits as a nearly racemic mixture. Data determined in extracts obtained by other techniques (liquid-liquid extraction, vacuum headspace technique) showed that the isolation procedure had no significant impact on the enantiomeric ratios.  相似文献   

2.
The odorants in Chinese jasmine green tea scented with jasmine flowers (Jasminum sambac) were separated from the infusion by adsorption to Porapak Q resin. Among the 66 compounds identified by GC and GC/MS, linalool (floral), methyl anthranilate (grape-like), 4-hexanolide (sweet), 4-nonanolide (sweet), (E)-2-hexenyl hexanoate (green), and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (sweet) were extracted as potent odorants by an aroma extract dilution analysis and sensory analysis. The enantiomeric ratios of linalool in jasmine tea and Jasminum sambac were determined by a chiral analysis for the first time in this study: 81.6% ee and 100% ee for the (R)-(-)-configuration, respectively. The jasmine tea flavor could be closely duplicated by a model mixture containing these six compounds on the basis of a sensory analysis. The omission of methyl anthranilate and the replacement of (R)-(-)-linalool by (S)-(+)-linalool led to great changes in the odor of the model. These two compounds were determined to be the key odorants of the jasmine tea flavor.  相似文献   

3.
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4.
The volatiles present in fresh, pink-fleshed Colombian guavas ( Psidium guajava, L.), variety regional rojo, were carefully isolated by solvent extraction followed by solvent-assisted flavor evaporation, and the aroma-active areas in the gas chromatogram were screened by application of the aroma extract dilution analysis. The results of the identification experiments in combination with the FD factors revealed 4-methoxy-2,5-dimethyl-3(2 H)-furanone, 4-hydroxy-2,5-dimethyl-3(2 H)-furanone, 3-sulfanylhexyl acetate, and 3-sulfanyl-1-hexanol followed by 3-hydroxy-4,5-dimethyl-2(5 H)-furanone, ( Z)-3-hexenal, trans-4,5-epoxy-( E)-2-decenal, cinnamyl alcohol, ethyl butanoate, hexanal, methional, and cinnamyl acetate as important aroma contributors. Enantioselective gas chromatography revealed an enantiomeric distribution close to the racemate in 3-sulfanylhexyl acetate as well as in 3-sulfanyl-1-hexanol. In addition, two fruity smelling diastereomeric methyl 2-hydroxy-3-methylpentanoates were identified as the ( R,S)- and the ( S,S)-isomers, whereas the ( S,R)- and ( R,R)-isomers were absent. Seven odorants were identified for the first time in guavas, among them 3-sulfanylhexyl acetate, 3-sulfanyl-1-hexanol, 3-hydroxy-4,5-dimethyl-2(5 H)-furanone, trans-4,5-epoxy-( E)-2-decenal, and methional were the most odor-active.  相似文献   

5.
Four new abscisic acid related compounds (1-4), together with (+)-abscisic acid (5), (+)-beta-D-glucopyranosyl abscisate (6), (6S,9R)-roseoside (7), and two lignan glucosides ((+)-pinoresinol mono-beta-D-glucopyranoside (8) and 3-(beta-D-glucopyranosyloxymethyl)-2- (4-hydroxy-3-methoxyphenyl)-5-(3-hydroxypropyl)-7-methoxy-(2R,3S)-dihydrobenzofuran (9)) were isolated from the antioxidative ethanol extract of prunes (Prunus domestica L.). The structures of 1-4 were elucidated on the basis of NMR and MS spectrometric data to be rel-5-(3S,8S-dihydroxy-1R,5S-dimethyl-7-oxa-6-oxobicyclo[3,2,1]oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid (1), rel-5-(3S,8S-dihydroxy-1R,5S-dimethyl-7-oxa-6-oxobicyclo[3,2,1]oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid 3'-O-beta-d-glucopyranoside (2), rel-5-(1R,5S-dimethyl-3R,4R,8S-trihydroxy-7-oxa-6-oxobicyclo[3,2,1]oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid (3), and rel-5-(1R,5S-dimethyl-3R,4R,8S-trihydroxy-7-oxabicyclo[3,2,1]- oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid (4). The antioxidant activities of these isolated compounds were evaluated on the basis of oxygen radical absorbance capacity (ORAC). The ORAC values of abscisic acid related compounds (1-7) were very low. Two lignans (8 and 9) were more effective antioxidants whose ORAC values were 1.09 and 2.33 micromol of Trolox equiv/micromol, respectively.  相似文献   

6.
Twenty-five compounds were identified from the dichloromethane and methanol extracts of royal jelly from Greece. Among them, 16 compounds are reported for the first time as royal jelly constituents, whereas 7 of them are isolated for the first time as natural products. The 7 new compounds were fatty acid derivatives: 10-acetoxydecanoic acid (1), trans-10-acetoxydec-2-enoic acid (2), 11-oxododecanoic acid (3), (11S)-hydroxydodecanoic acid (4), (10R,11R)-dihydroxydodecanoic acid (5), 3,11-dihydroxydodecanoic acid (6), and (11S),12-dihydroxydodecanoic acid (7). The structures of the isolated compounds were determined by spectroscopic methods, mainly by the concerted application of 1D and 2D NMR techniques (HMQC, HMBC) and mass spectrometry. The studied sample and the isolated compounds were tested for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi and exhibited interesting activities.  相似文献   

7.
Three terpene chlorohydrins found in cold-pressed orange oil were concentrated by silica adsorption chromatography and purified by preparative HPLC. Formation of these chlorohydrins was determined to be the result of a reaction of d-limonene, the major component of cold-pressed oil, with hypochlorous acid, found in chlorinated treatment water used in the oil recovery process. NMR analyses indicated that the major chlorohydrin present was the diequatorially substituted (1R,2R,4R)-2-chloro-8-p-menthen-1-ol (1). The other two compounds were the diaxial trans stereoisomer, (1S,2S,4R)-2-chloro-8-p-menthen-1-ol (2), and the dichlorohydrin, (1R,2R,4R)-2,9-dichloro-8-p-menthen-1-ol (3).  相似文献   

8.
The enantiomeric distribution of 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA) in Vitis vinifera wines was determined by combining two techniques: specific purification of volatile thiols from the wines using p-hydroxymercuribenzoate and separation of the chiral molecules by gas-phase chromatography on a cyclodextrin capillary column. The R and S enantiomer ratios of these two thiols in dry white Sauvignon blanc and Semillon wines are approximately 30:70 for A3MH and 50:50 for 3MH. However, in sweet white wines made from grapes affected by "noble rot" due to the development of Botrytis cinerea on ripe grapes, the proportion of the R and S forms of 3MH is in the vicinity of 30:70. During alcoholic fermentation, a change in the ratio of the two enantiomers of 3MH in dry white wines was observed. At the beginning of fermentation (around density 1.08), the S form represented over 60%; then, at lower density, as fermentation proceeded, the enatiomeric ratio approached 50:50. The ratio of the two 3MHA enantiomers remained constant throughout fermentation. On the contrary, the distribution of the two 3MH enantiomers changed very little during fermentation of the botrytized sweet wines. The perception thresholds for the R and S forms of 3MH in hydroalcoholic model solution are similar (50 and 60 ng/L). These two enantiomers have quite different aromas: The R form is fruitier, with a zesty aroma reminiscent of grapefruit, while the S form smells more of passion fruit. The perception thresholds of the R and S enantiomers of 3MHA are slightly different (9 and 2.5 ng/L). The less odoriferous R form is reminiscent of passion fruit, while the S form has a more herbaceous odor of boxwood.  相似文献   

9.
The biosynthesis of the monoterpene (S)-linalool and the sesquiterpene trans-(S)-nerolidol in fruits of Fragaria x ananassa Duch. cv. Eros and Florence and of the monoterpene (-)-alpha-pinene in Fragaria vesca was investigated by in vivo feeding experiments with [5,5-2H2]mevalonic acid lactone (d2-MVL) and [5,5-2H2]-1-deoxy-d-xylulose (d2-DOX). The feeding experiments indicate that (S)-linalool and trans-(S)-nerolidol in Fragaria x ananassa Duch. and (-)-alpha-pinene in F. vesca are exclusively synthesized via the cytosolic mevalonic acid pathway without any contribution from the plastidial 1-deoxy-D-xylulose/2-C-methyl-D-erythritol 4-phosphate (DOXP/MEP) route. Inhibition experiments revealed that even the presence of mevastatin, an export of plastid-derived isopentyl diphosphate/dimethylallyl diphosphate, cannot be induced. However, the enantioselective analysis shows that in Fragaria x ananassa Duch. cv. Eros and Florence both linalool enantiomers are present and that only (S)-linalool is labeled after administration of d2-MVL. Therefore, the origin of (R)-linalool in these fruits remains unknown. Contrarily, in Fragaria x ananassa Duch. foliage (R)-linalool is the dominant enantiomer. Feeding experiments revealed an incorporation of d2-MVL and d2-DOX at equal rates exclusively into (S)-linalool. Only in F. vesca foliage, where (R)-linalool is present at high enantiomeric purity (ee > 90%), is a de novo biosynthesis of the (R)-enantiomer via the DOXP/MEP pathway detectable. These results demonstrate a complex intraplant variation of (R)- and (S)-linalool biosynthesis via the cytosolic and plastidial route.  相似文献   

10.
Lytic activity of l-menthol (1) derivatives [(-)-(1S,3R,4S,6S)-6-hydroxymenthol (2), (-)-(1S,3R,4S)-1-hydroxymenthol (3), and (+)-(1S,3R,4R,6S)-6,8-dihydroxymenthol (4)] against the snow blight disease fungus, Micronectriella nivalis was investigated. Compounds 2, 3, and 4 had 85.0, 63.9, and 81.9% lytic activity, respectively, at a concentration of 0.2 mg/mL. The activity of each of the three compounds increased in a dose-response manner. To study the structure-activity relationship, acetyl esters of 1-4 [(-)-menthyl acetate (1Ac), (-)-6-hydroxymenthyl diacetate (2Ac), (-)-1-hydroxymenthyl 3-monoacetate (3Ac), and (-)-6,8-dihydroxymenthyl 3,6-diacetate (4Ac)] were synthesized with yields of 80.2-99.8% and were also assayed. The acetyl esters of 1Ac, 2Ac, 3Ac, and 4Ac had 51.2, 91.5, 66.0, and 95.2% lytic activity, respectively, at a concentration of 0.2 mg/mL, and these compounds showed further high lytic activity compared with the alcohols of 1-4. These acetyl esters also showed higher lytic activity as their concentration was increased. Of particular interest is the fact that 2Ac and 4Ac both had higher lytic activity at 0.05-0.2 mg/mL compared with copper 8-hydroxyquinolate, a standard chemical widely used to control snow blight. This is the first report on lytic activity of l-menthol derivatives.  相似文献   

11.
Wine lactone (i.e., 3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one, 1a/1b) was formed hydrolytically at wine pH from both racemic (E)-2,6-dimethyl-6-hydroxyocta-2,7-dienoic acid (3) and the corresponding glucose ester 2a at 45 °C but at room temperature was only formed from the acid 3. The glucose ester does not appear to be a significant precursor for the formation of wine lactone in wine. The slow formation of wine lactone from the free acid 3 indicates that the acid is not likely to be an important precursor to wine lactone in young wines unless present in high concentration (? 1 mg/L), but could be a significant precursor to wine lactone in wine that is several years old. The wine lactone formed in hydrolysates of the (6R)-enantiomer of 3 was partially enriched in the (3S,3aS,7aR)-enantiomer 1a when the hydrolysis was conducted at pH 3.2 and 100 °C in a closed vessel or under simultaneous distillation-extraction (SDE) conditions, and the enantiomeric excess (ee) varied from 5 to 22%. Hydrolysis of (6R)-3 in sealed ampules at 45 °C and at pH 3.0, 3.2, or 3.4 gave near-racemic wine lactone, but when the hydrolyses were conducted at room temperature, the product was enriched in the (3S,3aS,7aR)-enantiomer 1a and the ee was greater at higher pH (up to 60% at pH 3.4).  相似文献   

12.
(S)-(+)-O-methylmandelate esters of trans- and cis-1,3, 3-trimethyl-2-oxabicyclo[2.2.2]octan-5- and 6-ols (2- and 3-hydroxy-1,8-cineoles) were prepared, and eight diastereomers were separated. The absolute configuration of the asymmetric carbons of the cineole moiety of each diastereomer was determined by (1)H NMR data according to the Mosher theory. Each mandelate was reduced with LiAlH(4) to obtain optically pure hydroxy-1,8-cineoles, this being followed by acetylation to afford optically pure acetoxy-1, 8-cineoles. These acetates were subjected to chiral GC, using a cyclodextrin column, and the enantiomeric purity of trans- and cis-1, 3,3-trimethyl-2-oxabicyclo[2.2.2]octan-5- and 6-yl acetates in the aroma concentrate from the rhizomes of Alpinia galanga was determined as 93.9 (5S), 19.4 (5R), 63.5 (6R), and 100 (6R) % ee, respectively. The aroma character of each enantiomer was also evaluated by GC-sniffing.  相似文献   

13.
A method was developed for the analysis of salmon volatiles using solid-phase microextraction and gas chromatography-mass spectrometry. This method was used to monitor the volatiles of fresh king salmon (Oncorhynchus tshawytscha) stored in ambient air or in a 40:60 (v/v) mixture of CO2:N2 over time. The levels of several of the volatile compounds were found to change during storage, with some showing a clear difference between storage in air and storage in CO2:N2. Of these, several alcohols (cyclopentanol, Z-2-penten-1-ol, 1-penten-3-ol, and 1-octen-3-ol) and aldehydes (hexanal, octanal, E-2-pentenal, and E-2-hexenal) were identified as potential markers for salmon freshness. Several other volatiles (acetoin, ethyl benzene, propyl benzene, styrene, 3-methyl butanoic acid, and acetic acid) were identified as potential markers for salmon spoilage. A comparison of salmon harvested with and without the "rested harvesting" technique showed that E- and Z-isoeugenol levels were increased by the use of the isoeugenol based anesthetic. The use of the anesthetic did not affect the levels of any of the other compounds identified.  相似文献   

14.
Soybean (Glycine max) seed volatiles were analyzed using a solid phase microextraction (SPME) method combined with gas chromatography-mass spectrometry (GC-MS). Thirty volatile compounds already reported for soybean were recovered, and an additional 19 compounds not previously reported were identified or tentatively identified. The SPME method was utilized to compare the volatile profile of soybean seed at three distinct stages of development. Most of the newly reported compounds in soybean seed were aldehydes and ketones. During early periods of development at maturity stage R6, several volatiles were present at relatively high concentrations, including 3-hexanone, (E)-2-hexenal, 1-hexanol, and 3-octanone. At maturity stage R7 and R8, decreased amounts of 3-hexanone, (E)-2-hexenal, 1-hexanol, and 3-octanone were observed. At maturity stage R8 hexanal, (E)-2-heptenal, (E)-2-octenal, ethanol, 1-hexanol, and 1-octen-3-ol were detected at relatively high concentrations. SPME offers the ability to differentiate between the three soybean developmental stages that yield both fundamental and practical information.  相似文献   

15.
The effect of the partial NaCl replacement by other salts (potassium, calcium, and magnesium chloride) on the formation of volatile compounds through the processing of dry-cured ham was studied using solid-phase microextraction (SPME). Three salt formulations were considered, namely, I (100% NaCl), II (50% NaCl and 50% KCl), and III (55% NaCl, 25% KCl, 15% CaCl(2), and 5% MgCl(2)). There was an intense formation of volatile compounds throughout the processing of dry-cured hams, particularly during the "hot-cellar" stage. The differences between treatments were found to be more remarkable at the end of the curing process. Hams from formulations I and II had significantly higher amounts of lipid-derived volatiles such as hexanal than hams from formulation III, whereas the latter had significantly higher amounts of Strecker aldehydes and alcohols. Plausible mechanisms by which salt replacement may affect the generation of volatile compounds include the influence of such replacement on lipid oxidation and proteolysis phenomena. The potential influence of the volatiles profile on the aroma of the products is also addressed in the present paper.  相似文献   

16.
This study is the first of two publications that investigate the phenomena of coffee nonvolatiles interacting with coffee volatile compounds. The purpose was to identify which coffee nonvolatile(s) are responsible for the interactions observed between nonvolatile coffee brew constituents and thiols, sulfides, pyrroles, and diketones. The overall interaction of these compounds with coffee brews prepared with green coffee beans roasted at three different roasting levels (light, medium, and dark), purified nonvolatiles, and medium roasted coffee brew fractions (1% solids after 1 or 24 h) was measured using a headspace solid-phase microextraction technique. The dark roasted coffee brew was slightly more reactive toward the selected compounds than the light roasted coffee brew. Selected pure coffee constituents, such as caffeine, trigonelline, arabinogalactans, chlorogenic acid, and caffeic acid, showed few interactions with the coffee volatiles. Upon fractionation of medium roasted coffee brew by solid-phase extraction, dialysis, size exclusion chromatography, or anion exchange chromatography, characterization of each fraction, evaluation of the interactions with the aromas, and correlation between the chemical composition of the fractions and the magnitude of the interactions, the following general conclusions were drawn. (1) Low molecular weight and positively charged melanoidins present significant interactions. (2) Strong correlations were shown between the melanoidin and protein/peptide content, on one hand, and the extent of interactions, on the other hand (R = 0.83-0.98, depending on the volatile compound). (3) Chlorogenic acids and carbohydrates play a secondary role, because only weak correlations with the interactions were found in complex matrixes.  相似文献   

17.
A method for the screening of potential natural oak lactone precursors in oak wood extracts using LC-MS/MS combined with information-dependent acquisition was developed. The method was applied to extracts of American and French oak woods. As a result, cis-3-methyl-4-galloyloxyoctanoic acid (ring-opened cis-oak lactone gallate), (3S,4S)- and (3S,4R)-3-methyl-4-O-beta-D-glucopyranosyloctanoic acid (ring-opened cis- and trans-oak lactone glucoside), and (3S,4S)-3-methyl-4-O-(6'-O-galloyl)-beta-D-glucopyranosyloctanoic acid (ring-opened cis-oak lactone galloylglucoside) were identified as natural oak lactone precursors in the extracts by comparison with the respective synthetic reference compounds. In addition, the ring-opened oak lactone rutinoside was tentatively identified in the extracts. Three apparent isomers of the ring-opened cis-oak lactone galloylglucoside were also observed.  相似文献   

18.
The inhibitory effects of C-2 epimeric isomers of (-)-epigallocatechin-3-O-gallate (EGCG) and two O-methylated EGCG derivatives, (-)-epigallocatechin-3-O-(3-O-methyl)gallate (EGCG3'Me) and (-)-epigallocatechin-3-O-(4-O-methyl)gallate (EGCG4'Me), against oxazolone-induced type IV allergy in male mice were investigated. These compounds exhibited strong antiallergic effects by percutaneous administration at a dose of 0.13 mg/ear. The inhibition rates of (-)-gallocatechin-3-O-gallate (GCG), (-)-gallocatechin-3-O-(3-O-methyl)gallate (GCG3'Me), and (-)-gallocatechin-3-O-(4-O-methyl)gallate (GCG4'Me) on mouse type IV allergy were 52.1, 53.3, and 54.8%, respectively. However, the antiallergic effects were weaker than those of their corresponding original tea catechins (2R,3R type). The inhibition rates of those were 88.0, 73.2, and 77.6%, respectively. For all of the catechins tested, oral administration at a dose of 50 mg/kg body weight significantly suppressed the allergic symptoms. The inhibitory rates varied from 24.0 to 60.6%. No significant differences were observed between the effects of the epimers (2S,3R type) and their corresponding original catechins (2R,3R type). The antiallergic effects of tea catechins and their C-2 epimers observed in this study were dose-dependent. These results suggest that C-2 epimers of tea catechins, which are produced during heat processing at high temperatures, could be disadvantageous for the antiallergic effects on type IV allergy.  相似文献   

19.
The analysis of (R)-9- and (S)-9-hydroxy-10E,12Z-octadecadienoic acid as well as (R)-13- and (S)-13-hydroxy-9Z,11E-octadecadienoic acid (HODE) as free acids, esterified in triacylglycerols (storage lipids), and esterified in polar lipids (phospholipids, glycolipids, etc.) in barley, germinating barley, and finished malt was performed using [13-(18)O(1)]-(S)-13-HODE isotope dilution assays with GC-MS and straight- and chiral-phase HPLC. 9- and 13- HODE occur approximately racemically in barley, indicating an autoxidation. The enantiomeric excesses increase to 78% S for free 9-HODE and to 58% S for free 13-HODE in germinating barley as a result of lipoxygenase-2 (LOX-2) catalysis, but free HODEs are at low concentration. More than 90% of HODEs in barley and malt are esterified. In the storage lipids of green malt 53 mg/kg 9-HODE and 147 mg/kg 13-HODE were detected. This ratio of 30:70 reflects the regioselectivity of the LOX-2 enzyme in malt. In the polar lipids 45 mg/kg 9-HODE and 44 mg/kg 13-HODE were characterized. The latter indicate a hitherto unknown 9-lipoxygenase activity with polar lipids as substrates. During kilning the contents of most HODEs decreased significantly due to chemical and enzymatic degradation, whereas polar-esterified (R)-13-HODE increased (43%) in the finished malt.  相似文献   

20.
Syringa vulgaris L. inflorescences were fed with aqueous solutions of regioselectively deuterated compounds assumed to be precursors of lilac aldehyde and lilac alcohol, respectively. Volatiles were extracted by stir bar sorptive extraction (SBSE) and analyzed using enantioselective multidimensional gas chromatography/mass spectrometry (enantio-MDGC/MS); deuterium-labeled lilac aldehydes and lilac alcohols were separated from unlabeled stereoisomers on a fused silica capillary column, coated with heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin (DIME-beta-CD) (30%) in SE 52 (70%), as the chiral stationary phase. Feeding experiments with [5,5-(2)H(2)]mevalonic acid lactone 22 and [5,5-(2)H(2)]deoxy-d-xylose 23 indicate that the novel mevalonate independent 1-deoxy-d-xylose 5-phosphate/2C-methyl-d-erythritol 4-phosphate pathway is the dominant metabolic route for biosynthesis in lilac flowers. Additionally, bioconversion of deuterium-labeled d(5)-(R/S)-linalool 3, d(6)-(R)-linalool 21, d(5)-(R/S)-8-hydroxylinalool 6, d(5)-(R/S)-8-oxolinalool 7, d(5)-lilac aldehydes 8-11 and d(5)-lilac alcohols 12-15 into lilac during in vivo feeding experiments was investigated and the metabolic pathway is discussed. Incubation of petals with an aqueous solution of deuterated d(5)-(R/S)-linalool 3 indicates an autonomic terpene biosynthesis of lilac flavor compounds in the flower petals of lilac.  相似文献   

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