顶空固相微萃取-气相色谱-质谱法测定小米黄酒风味成分

为全面了解小米黄酒风味成分的构成和气味特征,优化了85μm聚丙烯酸酯(PA)、100μm聚二甲基硅氧烷(PDMS)、75μm碳分子筛(CAR)/PDMS、50/30μm二乙烯基苯(DVB)/CAR/PDMS萃取头提取小米黄酒风味成分的条件,采用顶空固相微萃取(headspace solid phase microextraction,HS-SPME)-气相色谱-质谱法(GC-MS)对风味成分进行定性、定量分析,并计算气味活性值(odor active value,OAV),同时利用OAV分析风味成分的气味特征和气味强度。结果显示:不同萃取头的最优萃取条件为样品量8 mL、萃取时间40 min、萃取温度60℃、NaCl添加量1.5 g。小米黄酒风味成分由醇、酯、含苯化合物、烃、酸、醛、酮、烯、酚和杂环类化合物构成,醇为主要风味成分。通过OAV确定了苯乙醇、苯乙烯、2-甲基萘、1-甲基萘、苯甲醛、苯乙醛、2-甲氧基-苯酚为小米黄酒气味特征成分,苯基乙醇、苯乙醛对气味贡献最大。PA和PDMS萃取头分别对极性和非极性化合物具有较好的吸附效果,CAR/PDMS和DVB/CAR/PDMS萃取头对中等极性化合物具有较好的吸附效果。该研究全面了解了小米黄酒风味成分的构成,为其产品开发及品质控制提供理论了依据。     

PDMS-Au复合基底上多环芳烃分子的表面增强拉曼光谱

利用聚二甲基硅氧烷(PDMS)对有机物的富集功能,通过在金纳米粒子单层膜(Au MLF)表面旋涂薄层PDMS膜制备PDMS-Au MLF复合表面增强拉曼光谱(SERS)基底.研究了SERS增强性能与旋涂液浓度及稀释溶剂间的关系,考察了复合基底增强活性的均匀性.研究发现,采用叔丁醇为稀释溶剂,浓度为2%(质量分数)的旋涂液时所得复合基底表面多环芳烃(PAHs)的SERS信号强度最高,且此基底SERS信号强度偏差小于10%.分别以PDMS-Au MLF复合材料和Au MLF作为基底,对比研究了对萘、蒽、菲和芘4种多环芳烃的SERS检测能力.结果表明,PDMS-Au MLF复合基底对以上4种有机物的检出限分别为10~(-6),10~(-7),10~(-8)及10~(-7)mol/L,相比于单一Au MLF基底,其检测限至少降低了1个数量级,这主要源自于PDMS对PAHs的富集作用,且此类复合基底可用于多种多环芳烃混合物的特征识别.     

Synthese en serie dedoublee d''un precurseur tricyclique du nor-18 methyl-8β-oestradiol

A diastereoisomeric mixture of cis- and trans-(10aR)- 7-hydroxy-10a-methyl-1-oxo-1,2,3,4,4a,9,10,10a-phenanthrene was synthesised from 2-methyl-1,3-cyclohexanedione. The enantiomers were separated at an early stage in the synthesis via a cyclohexane-carboxylic acid intermediate and no racemisation or inversion occurred at any step. The products are precursors of 8β-methyl 18-nor estradiol and of 8β-méthyl 18-nor 9β-estradiol respectively.     

Further sesquiterpenes from Polygonum viscosum (Polygonaceae)

Two new sesquiterpenes, 4-methoxycarbonyl-7-(1-methylethyl)-6-oxo-3,3a,7,8,8a-pentahydroazulene-1-carboxylic acid (viscoazusone) and 1,4-dimethoxy-carbonyl-7-(1-methylethyl)-6-oxo-3,3a,7,8,8a-pentahydroazulene (viscoazulone), were isolated from the whole plant of Polygonum viscosum. The structures of these compounds were determined by spectroscopic means.     

Screening of natural organic volatiles from Prunus mahaleb L. honey: coumarin and vomifoliol as nonspecific biomarkers

Headspace solid-phase microextraction (HS-SPME; PDMS/DVB fibre) and ultrasonic solvent extraction (USE; solvent A: pentane and diethyl ether (1:2 v/v), solvent B: dichloromethane) followed by gas chromatography and mass spectrometry (GC, GC-MS) were used for the analysis of Prunus mahaleb L. honey samples. Screening was focused toward chemical composition of natural organic volatiles to determine if it is useful as a method of determining honey-sourcing. A total of 34 compounds were identified in the headspace and 49 in the extracts that included terpenes, norisoprenoids and benzene derivatives, followed by minor percentages of aliphatic compounds and furan derivatives. High vomifoliol percentages (10.7%-24.2%) in both extracts (dominant in solvent B) and coumarin (0.3%-2.4%) from the extracts (more abundant in solvent A) and headspace (0.9%-1.8%) were considered characteristic for P. mahaleb honey and highlighted as potential nonspecific biomarkers of the honey's botanical origin. In addition, comparison with P. mahaleb flowers, leaves, bark and wood volatiles from our previous research revealed common compounds among norisoprenoids and benzene derivatives.     

顶空固相微萃取-气相色谱/质谱分析艾叶中的易挥发性成分

采用顶空固相微萃取(HS-SPME)与气相色谱/质谱(GC/MS)联用方法对艾叶中易挥发性成分进行了分析,并通过单因素和正交试验对影响HS-SPME的条件进行优化,确定了HS-SPME的最优参数为:50/30μm DVB/CAR/PDMS固相微萃取头、样品用量0.8g、萃取温度75℃、萃取时间50min、平衡时间30min、解吸4min。经GC/MS分析,共检出196种化合物,利用质谱解析结合保留指数定性确定结构132种,占易挥发性成分总量的94.01%。其中主要易挥发性成分是3-氨基吡唑、桉油精、β-杜松烯、顺-β-松油醇、3-甲基-2-丁烯酸-4-硝基苯基酯、3,6,6-三甲基-1,5-庚二烯-4-醇、6-甲基-3-(1-异丙基)-2-环己烯-1-酮、3-甲基-2-丁烯酸环丁酯。本文结果为艾叶易挥发性成分及其开发利用提供了一定的理论依据。     

Identification of volatile components in yak butter using SAFE, SDE and HS-SPME-GC/MS

The volatile components of yak butter were isolated by solvent-assisted flavour evaporation (SAFE), simultaneous distillation extraction (SDE; dichloromethane and diethyl ether as solvent, respectively) and headspace solid-phase microextraction (HS-SPME; CAR/PDMS, PDMS/DVB and DVB/CAR/PDMS fibre extraction, respectively) and were analysed by GC/MS. A total of 83 volatile components were identified under six different conditions, including 28 acids, 12 esters, 11 ketones, 10 lactones, 10 alcohols, 4 other compounds, 2 aldehydes, 2 unsaturated aldehydes, 1 furan, 1 sulphur-containing compound, 1 unsaturated alcohol and 1 unsatruated ketone. Among them, 51 were identified by SAFE, 58 by SDE (45 with dichloromethane as solvent and 41 with diethyl ether as solvent) and 40 by HS-SPME (26 with CAR/PDMS; 26 with PDMS/DVB and 32 with DVB/CAR/PDMS). Three pretreatment methods were compared to show that the volatile components obtained using different methods varied greatly, both in terms of categories and in content. Therefore, a multi-pretreatment method should be adopted, together with GC/MS. A total of 25 aroma-active compounds were detected by gas chromatography-olfactometry, among which 20 aroma-active compounds were found by SDE (14 with dichloromethane as solvent and 14 with diethyl ether as solvent) and 17 by SAFE.     

Study of the effect of different fiber coatings and extraction conditions on dry cured ham volatile compounds extracted by solid-phase microextraction (SPME)

Extraction of dry cured ham volatile compounds by solid-phase microextraction (SPME) was optimized. Different fiber coatings (carboxen/polydimethylsiloxane (CAR/PDMS), divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS), polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB)), times of extraction (15, 30, 60 min) and sample preparation (ground samples and homogenates with NaCl saturated solution) were assayed. CAR/PDMS and DVB/CAR/PDMS fiber coatings extracted more than 100 volatile compounds and showed the highest area counts for most volatile compounds. CAR/PDMS coating extracted better those compounds whose Kovats index (KI) was lower than 980 (on average) and DVB/CAR/PDMS those with higher KI. Fifteen minutes of extraction provided a volatile compound profile with lower area counts for most compounds and qualitatively different to that obtained with 30 and 60 min of extraction. Homogenates gave a different profile compared to ground samples, with lower total counts for most compounds but higher proportion of aldehydes, and presence of several compounds not found in ground samples.     

Oxidation of 2-methoxy-6-(1-methylethyl)naphthalene with oxygen

Abstract  

Aerobic oxidation of 2-methoxy-6-(1-methylethyl)naphthalene to hydroperoxide, alcohol, and ketone, is reported. These compounds, particularly 2-acetyl-6-methoxynaphthalene, are important intermediates in naproxen synthesis. N-Hydroxyphthalimide is shown here to be an efficient catalyst for oxidation to the hydroperoxide, 2-methoxy-6-(1-hydroperoxy-1-methylethyl)naphthalene, with a yield of 87%. However, the ketone and alcohol were obtained with lower yields, with a maximum yield of 13% for the ketone and 27% for the alcohol, using N-hydroxyphthalimide and Cu(II) acetylacetonate as a catalyst. The synthesis of the products 2-acetyl-6-methoxynaphthalene and 2-methoxy-6-(1-hydroxy-1-methylethyl)naphthalene via an initial oxidation step to the hydroperoxide followed by a hydroperoxide decomposition step is shown to be more efficient; the ketone and alcohol were obtained from 2-methoxy-6-(1-methylethyl)naphthalene with yields of 40 and 56%, respectively.     

Optimization of headspace solid phase microextraction for gas chromatography/mass spectrometry analysis of widely different volatility and polarity terpenoids in olibanum

The aim of this study was the optimization of headspace SPME conditions for trapping diterpenes present in frankincense (olibanum). Diterpenes like cembrenes or incensole and its derivatives are characteristic of olibanum. So in order to detect by SPME the occurrence of olibanum in archeological objects, it appears essential to have the best extraction conditions for these diterpenes that will be in very small quantities. Both sampling time and extraction temperature were studied and five fiber coatings were tested: polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), carboxen/polydimethylsiloxane (CAR/PDMS), divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) and carbowax/divinylbenzene (CW/DVB). The PDMS/DVB fiber was found to be the most efficient for trapping olibanum characteristic diterpenes, with a sampling time of 1 h and a sampling temperature of 80 degrees C.     

The Relative Stabilities of Substituted cis- and trans-1,2,3,4,4a,9,10,10a-Octahydrophenanthrenes,Including Configurational Corrections in the Elad-Ginsburg Morphine Synthesis

The relative configuration of the title compounds has been determined by ¹H-NMR measurements at 300 MHz. In contradistinction to prevailing opinion, it was found that 4-oxo derivatives prefer the cis-configuration. While the cis/trans ratio is 82:18 for the parent 1,2,3,4,4a,9,10,10a-octahydrophenanthrene-4,9-dione, the trans-isomers of C(5)-substituted derivatives cannot be detected under the conditions of equilibration. The cis-configuration is retained upon acetalization of the 4-oxo derivative. A warning is issued regarding the assigned configurations of certain intermediates in the Elad-Ginsburg synthesis of morphine.     

Effectiveness of different solid-phase microextraction fibres for differentiation of selected Madeira island fruits based on their volatile metabolite profile--identification of novel compounds

A headspace solid-phase microextraction (HS-SPME) procedure based on five commercialised fibres (85 μm polyacrylate - PA, 100 μm polydimethylsiloxane - PDMS, 65 μm polydimethylsiloxane/divinylbenzene - PDMS/DVB, 70 μm carbowax/divinylbenzene - CW/DVB and 85 μm carboxen/polydimethylsiloxane - CAR/PDMS) is presented for the characterization of the volatile metabolite profile of four selected Madeira island fruit species, lemon (Citrus limon), kiwi (Actinidia deliciosa), papaya (Carica papaya L.) and Chickasaw plum (Prunus angustifolia). The isolation of metabolites was followed by thermal desorption gas chromatography-quadrupole mass spectrometry (GC-qMS) methodology. The performance of the target fibres was evaluated and compared. The SPME fibre coated with CW/DVB afforded the highest extraction efficiency in kiwi and papaya pulps, while in lemon and plum the same was achieved with PMDS/DVB fibre. This procedure allowed for the identification of 80 compounds, 41 in kiwi, 24 in plums, 23 in papaya and 20 in lemon. Considering the best extraction conditions, the most abundant volatiles identified in kiwi were the intense aldehydes and ethyl esters such as (E)-2-hexenal and ethyl butyrate, while in Chicasaw plum predominate 2-hexenal, 2-methyl-4-pentenal, hexanal, (Z)-3-hexenol and cyclohexylene oxide. The major compounds identified in the papaya pulp were benzyl isothiocyanate, linalool oxide, furfural, hydroxypropanone, linalool and acetic acid. Finally, lemon was shown to be the most divergent of the four fruits, being its aroma profile composed almost exclusively by terpens, namely limonene, γ-terpinene, o-cymene and α-terpinolene. Thirty two volatiles were identified for the first time in the fruit or close related species analysed and 14 volatiles are reported as novel volatile metabolites in fruits. This includes 5 new compounds in kiwi (2-cyclohexene-1,4-dione, furyl hydroxymethyl ketone, 4-hydroxydihydro-2(3H)-furanone, 5-acetoxymethyl-2-furaldehyde and ethanedioic acid), 4 in plum (4-hydroxydihydro-2(3H)-furanone, 5-methyl-2-pyrazinylmethanol, cyclohexylene oxide and 1-methylcyclohexene), 4 in papaya (octaethyleneglycol, 1,2-cyclopentanedione, 3-methyl-1,2-cyclopentanedione and 2-furyl methyl ketone) and 2 in lemon (geranyl farnesate and safranal). It is noteworthy that among the 15 volatile metabolites identified in papaya, 3-methyl-1,2-cyclopentanedione was previously described as a novel PPARγ (peroxisome proliferator-activated receptor γ) agonist, having a potential to minimize inflammation.     

Synthesis and photophysical properties of models for twisted PRODAN and dimethylaminonaphthonitrile

The synthesis and photophysical properties of 7-cyano-3,4-dihydro-2H-1,4-ethano-benzo[g]quinoline and 3,4-dihydro-2H-1,4-ethano-7-propionyl-benzo[g]quinoline are reported. These compounds possess a quinuclidine substructure that locks the tertiary amino group perpendicular to the naphthalene ring. Their excited states are models for the twisted excited states of 2-(dimethylamino)-6-naphthonitrile (DMANN) and 6-propionyl-2-(dimethylamino)naphthlene (PRODAN). In contrast to DMANN and PRODAN, the fluorescence of these twisted derivatives is strongly deactivated in polar solvents. Neither DMANN nor PRODAN likely emit from TICT excited states.     

Access to ring-fused homo- and heteroaromatic derivatives via an initial ring-opening of 3-nitro-4-(phenylsulfonyl)thiophene

Within an overall ring-opening/ring-forming protocol, the (E,E)-4-methylthio-2-nitro-3-phenylsulfonyl-1-pyrrolidino-1,3-butadiene (7) [derived from the initial opening of 3-nitro-4-(phenylsulfonyl)thiophene (6) with pyrrolidine and silver nitrate in EtOH] is revealed to be an excellent precursor of nitro(phenylsulfonyl) derivatives of ring-fused aromatic (naphthalene, phenanthrene) or heteroaromatic (benzothiophene) compounds whose substitution pattern cannot be easily achieved by conventional methods. The key step is represented by a thermal electrocyclic rearrangement of (E,E)-1-aryl-4-methylsulfonyl-2-nitro-3-phenylsulfonyl-1,3-butadienes (9), which, thanks to proper geometric and electronic factors, occurs in unprecedentedly mild conditions and is followed by an irreversible, concerted syn beta-elimination of methanesulfinic acid to aromatize the newly formed cyclohexadienic ring.     

Synthesis of 1,2,3,4,4a,5-hexahydropyrido[1′,2′:4,5][1,4]oxazino[2,3-b]quinoxaline derivatives

Reactions of 2,3-dichloroquinoxalines with 2-(hydroxymethyl)piperidine resulted in a series of 1,2,3,4,4a,5-hexahydropyrido[1′,2′:4,5][1,4]oxazino[2,3-b]quinoxaline derivatives. The structures of the products were confirmed by nmr and x-ray crystallography.     

Reaction of 2,3-diaminomaleonitrile with diones

2,3-Diaminomaleonitrile (DAMN) was allowed to react with 2,6-heptanedione to produce (2Z)-2-amino-3-[(1E)-3-methylcyclohex-2-enylideneamino]but-2-enedinitrile and (2Z)-2-amino-3-[(1Z)-3-methylcyclohex-2-enylideneamino]but-2-enedinitrile. The reaction of DAMN with 2,7-octanedione yielded trans-5,8a-dimethyl-1,5a,6,7,8,8a-hexahydrocyclopenta[e]-1,4-diazepine-2,3-dicarbonitrile. DAMN reacted with 2,8-nonanedione to afford trans- and cis-5,9a-dimethyl-5a,6,7,8,9,9a-hexahydro-1H-benzo[e]-1,4-diazepine-2,3-dicarbonitrile. These compounds were characterized by X-ray crystallography, NMR spectroscopy, and DFT calculations.     

Determination of phthalates in water using fiber introduction mass spectrometry

Fiber introduction mass spectrometry (FIMS)-a direct coupling of SPME and MS-using selective ion monitoring (SIM) was used to detect and quantify dimethylphthalate (DMP), diethylphthalate (DEP) and dipropylphthalate (DPP) in mineral water. In FIMS, a chromatographic silicone septum is the only barrier between ambient and the high-vacuum mass spectrometer, permitting direct introduction of the SPME fiber into the ionization region of the equipment. After their thermal desorption and ionization and dissociation, the extracted phthalates are detected and quantitated by MS. Three types of SPME fibers were screened for best analyte sorption/desorption behaviors: 100 microm polydimethylsiloxane (PDMS), 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) and 65 microm Carbowax/divinylbenzene (CW/DVB). The PDMS/DVB and CW/DVB fibers were then evaluated for precision, and quantitative figures of merit were assessed for extractions using the PDMS/DVB fiber, which displayed the best overall performance. FIMS with the PDMS/DVB fiber allows simple extraction and MS detection and quantitation of DMP in water with good linearity and precision, and at concentrations as low as 3.6 microg L(-1). The LD and LQ of FIMS are below the maximum phthalate concentration allowed by the USEPA for drinking water (6 microg L(-1)).     

Synthetic, crystallographic, computational, and biological studies of 1,4-difluorobenzo[c]phenanthrene and its metabolites

1,4-Difluorobenzo[c]phenanthrene (1,4-DFBcPh) and its putative metabolites, the dihydrodiol and diol epoxides, have been synthesized and structurally characterized, and the extent of DNA binding by the metabolites has been assessed. 1,4-DFBcPh and 1,4-difluoro-10-methoxybenzo[c]phenanthrene were prepared by photochemical cyclization of appropriate naphthylphenylethylenes. The dihydrodiol was synthesized from 1,4-difluoro-10-methoxybenzo[c]phenanthrene, and the diol epoxides were diastereoselectively synthesized from the dihydrodiol. Interesting differences were noted in 1H NMR spectra of the series 1 (syn) diol epoxides of benzo[c]phenanthrene (BcPh) and 1,4-DFBcPh; the BcPh diol epoxide displays a quasi-diequatorial orientation of the hydroxyl groups, but in the 1,4-DFBcPh case these are diaxially disposed. This difference probably stems from the presence of the fjord-region fluorine atom in 1,4-DFBcPh. A through-space, fjord-region H-F coupling has also been observed for 1,4-DFBcPh and its derivatives. Comparative X-ray crystallographic analyses of BcPh and 1,4-DFBcPh and their dihydrodiols show that introduction of fluorine increases the molecular distortion by about 6-7 degrees . As a guide to estimating the molecular distortion and its effects, and for comparison with the X-ray structures in known cases, optimized structures of BcPh, 1,4-DFBcPh, and 1,4-DMBcPh (the dimethyl analogue) as well as their dihydrodiols and diol epoxides were computed. Relative aromaticities of these compounds were assessed by nucleus-independent chemical shift calculations, and 13C NMR chemical shifts were computed by gauge-inducing atomic orbital calculations. 1,4-DFBcPh and its dihydrodiol were subjected to metabolism, and the amount of DNA binding in human breast cancer MCF-7 cells was assessed. The extent of DNA binding was then compared with that for BcPh and its dihydrodiol and the potent carcinogen benzo[a]pyrene. The 1,4-DFBcPh series 2 (anti) diol epoxide-derived DNA adducts were also compared with those arising from intracellular oxidation of the dihydrodiol with subsequent DNA binding. These experiments showed that increased molecular distortion decreased metabolic activation to the terminal metabolites but that diol epoxide metabolites that are formed are the DNA-damaging species.     

Monitoring the emission of volatile organic compounds from flowers of Jasminum sambac using solid-phase micro-extraction fibers and gas chromatography with mass spectrometry detection

Solid-phase micro-extraction (SPME) was studied as a solvent free alternative method for the extraction and characterization of volatile compounds in intact and plucked flowers of Jasminum sambac at different day time intervals using gas chromatography (GC-FID) and gas chromatography-quadrupole mass spectrometry. The analytes identified included alcohols, esters, phenolic compounds, and terpenoids. The main constituents identified in the flower aroma using different fibers were cis-3-hexenyl acetate, (E)-beta-ocimene, linalool, benzyl acetate, and (E,E)-alpha-farnesene. The benzyl acetate proportion decreased from morning to afternoon and then increased in evening collections. PDMS fiber showed a high proportion of (E,E)-alpha-farnesene in jasmine floral aroma. Among other constituents identified, cis-3-hexenyl acetate, linalool, and benzyl acetate were major aroma contributors in plucked and living flowers extracts using PDMS/DVB, Carboxen/PDMS, and DVB/Carboxen/PDMS fibers. PDMS/DVB recorded the highest emission for benzyl acetate while the (E)-beta-ocimene proportion was highest in DVB/Carboxen/PDMS when compared with the rest. The highest linalool content, with increasing proportion from morning to noon, was found using mixed coating fibers. Almost negligible volatile adsorption was recorded for the polyacrylate fiber for intact flower aroma, whereas it was most effective for benzyl acetate, followed by indole under plucked conditions. Moreover, the highest amounts extracted, evaluated from the sum of peak areas, were achieved using Carboxen/PDMS, and DVB/Carboxen/PDMS. Introduction of a rapid, and solvent free SPME method for the analysis of multicomponent volatiles can be successfully employed to monitor the extraction and characterization of flower aroma constituents.     

Novel photochemical reaction of indole with naphthalene and phenanthrene in the solid state

Irradiation of mixed crystals of indole and naphthalene gave an addition product, 1-(1,4-dihydro-1-naphthyl)indole ( ), while irradiation in solution gave another product in addition to . Similar solid-state photoreaction of indole and phenanthrene gave .