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GC/IRMS analysis of mandarin essential oils. 1. δ13CPDB and δ15NAIR values of methyl N-methylanthranilate
Abstract
The δ13CPDB and δ15NAIR values of methyl N-methylanthranilate from mandarin essential oils have been measured by capillary gas chromatography, on-line coupled with isotope ratio mass spectrometry (GC/IRMS). Cold-pressed and distilled mandarin peel oils of different origins and petitgrain oils mandarinier as well as reference substances of methyl N-methylanthranilate and methyl anthranilate were investigated. The combination of the δ13C and δ15N values is useful in the authenticity control of mandarin oils. Keywords: GC/IRMS; δ13CPDB and δ15NAIR values; methyl N-methylanthranilate; mandarin essential oil; Citrus reticulata Blanco
... Analyses GC-C/P-IRMS complémentaires (Faulhaber et al., 1997a(Faulhaber et al., , 1997b Mandarine α-thuyène, α-pinène, camphène, β-pinène, sabinène, α- (Kreck et al., 2002) Neroli, petitgrain α-pinène, β-pinène, limonène, terpinène-4-ol, nérolidol Données d'échantillons naturels (Juchelka et al., 1996) Lavande Linalol, acétate de linalyle Données d'échantillons naturels. Analyses GC-C/P-IRMS complémentaires (Jung et al., 2005) Origan, sarriette, thym, fenouil α-pinène, limonène, terpinène-4-ol, β-pinène, linalol, bornéol, fenchone, camphre Différences entre échantillons naturels et synthèse. ...
... Certaines études, réalisées en GC-C/P-IRMS, ont permis de mettre en évidence des corrélations entre molécules de mêmes origines, par exemple dans le cas de l'étude de la mandarine (Faulhaber et al., 1997a(Faulhaber et al., , 1997b. Une étude multi isotopes permet aussi de mettre en évidence des relations de linéarité entre ratios isotopiques. ...
... En effet, les méthodes multi techniques permettent d'améliorer l'authentification d'une matière en croisant les diagnostics (Mosandl, 1995). (Faulhaber et al., 1997b(Faulhaber et al., , 1997a ...
Les matières naturelles aromatiques, telles que les huiles essentielles, que l’on retrouve sur le marché, ne sont pas toujours authentiques, bien que ces produits soient vendus comme étant 100% purs et naturels. Certains fournisseurs fraudent leurs produits afin de réduire les coûts de production, d’améliorer la qualité des huiles essentielles ou encore pour augmenter artificiellement les volumes de production. Les huiles essentielles sont adultérées en ajoutant des produits à moindre coût, incluant des matières naturelles moins chères et des molécules d’origine pétrochimique. Des méthodes d’authentification appropriées sont nécessaires pour contrôler la naturalité et la pureté des huiles essentielles. La détermination des ratios isotopiques stables et l’analyse énantiosélective de composés spécifiques, associées à la recherche de traces de précurseurs de synthèses, permettent d’authentifier de nombreuses huiles essentielles (gaulthérie, alliacées, néroli, menthe crépue, cannelle et cypriol). Le contrôle de ces produits naturels requiert l’établissement de banques de données, constituées d’échantillons parfaitement tracés pour l’authenticité de leurs origines. La méthodologie mise en place a permis de développer de nouveaux outils pertinents pour l’authentification, comprenant le développement de l’analyse isotopique de composés ciblés pour la mesure du δ18O et du δ34S, et d’identifier de nouvelles fraudes, comprenant les ajouts de composés enrichis en 14C et les molécules issues d’hémisynthèses.
... This is remarkably different from that of nature-identical vanillin ( 13 C = -24.9 to -36.2‰) which is produced from lignin (by oxidative degradation), cinnamic aldehyde (by retro aldol condensation), eugenol (by isomerisation and degradation) or guaiacol (by chemical synthesis) [3,256,259]. Therefore, the 13 C-value by itself would normally be a reliable proof for [248] the authenticity of vanillin. However, adulterators have meanwhile learned to imitate the 13 C-value of natural vanillin by blending "nature-identical" vanillin with products artificially enriched in 13 C; as this enrichment is usually performed in the methoxy or carbonyl group, the proof of this adulteration is possible by positional isotope analysis [244,273] (see 6.2.2.4.4). ...
... distinction possible [344] For certain aroma compounds carbon and hydrogen isotope analysis has meanwhile been supplemented by that of oxygen, nitrogen and/or sulphur stable isotopes. The substances that have been investigated up to now are allylisothiocyanate (mustard oil) using 15 N-and 34 S-analysis, dimethylsulphide (onion oil, garlic oil) using 34 S-analysis [293,363], dimethylanthranilate (grapefruit oil) using 15 N- [247,248] and esters using 18 O-determination [343]. Due to the increasing demand for "salty" flavours, which often contain nitrogen and/or sulphur atoms, the isotopic analysis of both elements in flavours will be more important in the future. ...
... Its methylated derivative, methyl N-methylanthranilate, was detected in some of the samples, mainly those from the region of Chania. This compound is characteristic of mandarin peel essential oil (Faulhaber, Hener, & Mosandl, 1997). 1-p-Menthen-9al has been reported before in haze honey (Shimoda, Wu, & Osajima, 1996) and in different types of honey from Sicily (Verzera et al., 2001). ...
... f See Kreck et al. (2003). g See Faulhaber et al. (1997). h See Bonnländer and Winterhalter (2000). ...
The aroma of Greek citrus honey was investigated by means of SPME–GC/MS analysis. A total of 61 compounds could be identified, with lilac aldehydes predominating the extract. These compounds can be considered the most powerful markers for citrus honey. Additionally, the two isomeric dehydroxy linaloxides, lavender lactone, dill ether, the four isomers of 1-p-menthen-9-al, methyl anthranilate and nerolidol could aid the botanical discrimination. Of the compounds identified, five are reported as honey constituents for the first time, that is trans- and cis-dehydroxy linaloxides, 1,8-menthadien-4-ol, limonene-10-ol and methyl N-methylanthranilate.
... This compound is responsible for the typical aroma of tangerine (Schieberle et al., 2003), and it is used as a fragrance ingredient in cosmetics and detergents (SCCS, 2011); in fact, it provides a mandarin flavour. Potential precursors of this compound are methyl anthranilate and anthranilic acid as intermediates in the aromatic amino acid pathway (Faulhaber et al., 1997). Furthermore, terpinene, linalool, terpineol, decanal, perillaldehyde, carvacrol, caryophyllene and cadinene according to Safranko et al. (2021), farnesene according to Xiong & Chen (2020) and 1,1dimethoxyoctane were also identified. ...
This work investigated the extraction of bioactive compounds from citrus peels, an agri‐food waste. Carbon dioxide (CO2), an eco‐friendly solvent, was used under liquid and supercritical conditions to perform the extractions from orange, tangerine and lemon peels. The possibility of using ethanol as a cosolvent at small percentages up to 20% was also studied. The extraction yield, total polyphenolic content, individual polyphenolic profile, antiradical activity and volatile organic compounds of the extracts were evaluated.
The highest yields were obtained when 20% ethanol was used as a cosolvent in both liquid (at 20 MPa and 20 °C) and supercritical (at 30 MPa and 60 °C) CO2 extraction. In addition, the extracts obtained with liquid CO2 + 20% ethanol showed the highest content of naringin (35.26, 44.05 and 19.86 mg g‐1 in orange, tangerine and lemon peel extracts, respectively) and terpenes, in particular limonene. This type of extract also showed the highest antiradical activity (31.78–59.51 µmolTE g‐1) as measured by both ABTS·+ and DPPH·.
These findings show that the extraction with a liquid CO2 and ethanol mixture could be a valid alternative to traditional solvent extraction using 80% less organic solvent and producing extracts with high antiradical capacity and rich in volatile organic compounds.
... Later, the same authors determined the values of δ 13 C and δ 15 N relative to methyl-N-methyl anthranilate in mandarin peel oils of different geographical origin, in petitgrain mandarinier oils and in commercially available standards (35). The isotope ratios resulted to be a useful tool to discriminate between different geographical origins of the samples and to assess their authenticity. ...
The theme of adulteration of natural flavours is briefly discussed along with the most common analytical tools used to unveil possible frauds of Citrus essential oils. Therefore, the article focuses on the main analytical approaches used for carbon isotope ratio determination of citrus secondary metabolites. Different applications of carbon isotope ratios mass spectrometry on the major Citrus products are revised to highlight the potentialities of this tool for authenticity assessment of Citrus essential oils and flavours. A deeper discussion is given on the most recent literature produced by the authors with a further evaluation of the complex picture emerged from their results. The data are overall considered to evaluate possible correlations among the carbon isotope ratios of different Citrus secondary metabolites and to prove whether univocal assessment of the genuineness of Citrus essential oils can be performed based on this analytical approach.
... Methyl-N-methylanthranilate is an important aroma compound from mandarin peel oil, which only in a few cases has been reported as a constituent of the Citrus essential oils, since GC analysis are dedicated to determine the presence of terpene type compounds only (Kamal et al., 2011;Mondello et al., 2003;Verzera et al., 2000). However, it has been used in some cases to recognize the authenticity of essential mandarin oils in several parts of the world (Faulhaber et al., 1997). ...
Context:
More analgesic compounds are needed in medicine against pain since the available drugs displayed secondary effects. Natural products are a source of molecules to develop new analgesics, using the information of plants, applied against pain, with effects such as pungency, tingling, and needle, due to their possible role in the central nervous system (NCS). Citrus reticulata Blanco (Rutaceae) leaves are usually bitten to flavor the mouth and possess this type effect in lips and tongues; due to this fact the structure of the bioctive compound could be the source of other types of analgesics.
Objective:
The objective of this study is to determine the causal agent of the pungent effect in mandarin essential oil.
Materials and methods:
Mandarin essential oil was obtained and then purified by column chromatography. Each fraction was tested and pungency was detected only in the first fraction which was pure.
Results:
The compound responsible for the pungency in the essential oils of leaves from Citrus reticulata (mandarin) was purified and the structure was assigned as methyl-N-methylanthranilate, on the basis of NMR 1D and 2D and MS. This substance corresponds to another type of molecule involving an antinociceptive effect.
Conclusions:
Terpenes are compounds found in essential oils. The compound responsible for the pungency of mandarin and other citrus leaves was isolated, and surprisingly it was identified as a methyl-N-methylanthranilate. This kind of molecules with this activity could be used to discover new analgesics in human therapy against pain.
... Previous studies had demonstrated pollinator attractant and bird repellent actions (Faulhaber et al., 1997;Jabalpurwala et al., 2009), as well as antibacterial and antifungal activities for methyl N-methylanthranilate (Heindel et al., 1968). Recently, Radulović et al. (2013) demonstrated that the pre-treatment of mice with isopropyl and methyl N-methylanthranilate developed anxiolytic and antidepressant-like effects, and a prolongation of diazepaminduced sleep, suggesting an interaction with the gammaaminobutyric receptor complex. ...
... Using the guidelines suggested by Braunsdorf et al. (1993a) and Mosandl (1995) , the carbon isotope ratio has largely been applied to evaluate fl avor and fragrance genuineness. The matrices studied, not including bergamot, were balm oils (Hener et al. 1995), coriander oils (Frank et al. 1995), orange oils (Braunsdorf et al. 1993b), mandarin oils (Faulhaber et al. 1997aFaulhaber et al. , 1997b Schipilliti et al. 2010), lemon (Schipilliti et al. 2011a), mentha piperita oils (Faber et al. 1995), volatile components from strawberry (Schumacher et al. 1995; Schipilliti et al. 2011b) and apple (Karl et al. 1994), and nerolì and lime oils (Bonaccorsi et al. 2011aBonaccorsi et al. , 2011b). Applications of IRMS to fl avor and fragrances were revised by Meier-Augenstein (1999) and by Mosandl (2007). ...
13.1 INTRODUCTION Bergamot peel oil is a valuable product for its olfactory properties and high commer-cial value. As unfortunately often happens, bergamot oil is subject to adulteration practices by industrial or commercial operators to increase their profi t. The fi rst information on bergamot adulteration is given by De Domenico (1854) from Reggio Calabria, who wrote a book on the medical properties of bergamot oil. De Domenico reported the addition to cold-extracted bergamot oil of a mixture obtained with "turpentine" (an essential oil extracted from the pine tree also known as turpentine oil) and sweet orange or lemon oils or oils obtained by distillation or cold extraction of unripe fruits of bergamot (called bergamottella) prematurely fallen from the trees. Similar practices were probably also applied for the adulteration of other citrus oils. Later, after Semmler and Tiemann (1892) found that linalyl acetate is the main com-ponent of bergamot oil, it became common practice to add esters obtained from sources different from bergamot, and of lower commercial value, to adulterate bergamot oil.
... However, considering that modern adulterations of essential oils as well as many food products are becoming harder to unveil, the determination of the d 13 C of target components, by means of stable isotope ratio analysis, has become a rapid and convenient tool for authenticity assessment. In fact, the analysis of the carbon isotopic composition can be very useful for the determination of geographic origin, an adulteration of natural essential oils with synthetic or natural compounds, prohibited farming procedures or production methods [6][7][8][9][10][11][12][13][14]. ...
Cold-pressed mandarin essential oils are products of great economic importance in many parts of the world and are used in perfumery, as well as in food products. Reconstituted mandarin oils are easy to find on the market; useful information on essential oil authenticity, quality, extraction technique, geographic origin and biogenesis can be attained through high-resolution GC of the volatile fraction, or enantioselective GC, using different chiral stationary phases. Stable isotope ratio analysis has gained considerable interest for the unveiling of citrus oil adulteration, detecting small differences in the isotopic carbon composition and providing plenty of information concerning the discrimination among products of different geographical origin and the adulteration of natural essential oils with synthetic or natural compounds. In the present research, the authenticity of several mandarin essential oils was assessed through the employment of GC hyphenated to isotope ratio MS, conventional GC flame ionization detector, enantioselective GC and HPLC. Commercial mandarin oils and industrial natural (declared as such) mandarin essential oils, characterized by different harvest periods and geographic origins, were subjected to analysis. The results attained were compared with those of genuine cold-pressed Italian mandarin oils, obtained during the 2008-2009 harvest season.
The determination of food adulteration is of primary importance in protecting consumers against fraud and to reveal fraudulent use of deceptive additives in the food industry. Another important factor affecting the behaviors of consumers of agricultural products that has also attracted considerable attention from an analytical determination standpoint is that of geographical origin as consumers are increasingly viewing quality being linked to it. This study comprises a review of selected recent peer-reviewed publications on the topic of isotope ratio mass spectrometry (IRMS) in food analysis. The technique is already verified by plenty of studies in determination of food adulteration. Geographical origin authentication and adulteration determination are two practical implementations of the technique towards the assessment of food product quality. Geographical origin authentication studies combine various additional analytical techniques with IRMS in many cases (ICP-MS, NMR, etc.). The publications covered establish the suitability of multi-elemental, bulk, and compound specific stable isotope analysis for geographical origin authentication. Herein we report here EA/LC-IRMS method development and evaluation of data are presented.
Keywords: EA/LC-IRMS; food adulteration; food analysis; adulteration detection; geographical origin authentication.
The quorum sensing (QS) inhibition effect of methyl N-methylanthranilate (MMA) from Pericarpium Citri Reticulatae Chachiensis against foodborne pathogen Pseudomonas aeruginosa was reported for the first time. MMA effectively attenuated QS related virulence factors production and biofilm formation, while suppressed expression of a dozen of QS related genes. Untargeted LC-MS metabolomics revealed 108 significantly altered metabolites after MMA treatment. They indicated that MMA addition reduced the efficiency of TCA cycle and antioxidant systems, disturbed amino acid and nucleotide metabolism, increased unsaturated fatty acid and decreased peptidoglycan components, which might ultimately attenuate P. aeruginosa pathogenicity and restrain biofilm formation. Physiological characterization confirmed the compromised membrane integrity and increased intracellular oxidative stress after MMA treatment. Furthermore, metabolomics data implied that MMA inhibition on QS might exert through disrupting QS autoinducer PQS biosynthesis, which was supported by molecular docking. Our data indicated that MMA could be used as a novel QS inhibitor and anti-biofilm agent to improve food safety. It also provided new insight in the possible underlying inhibition mechanism of MMA and the response of P. aeruginosa to MMA.
Sensory Analysis in Quality ControlAnalytical Methods
Microbiological Testing
Angenehme Düfte sind für das Wohlbefinden des Menschen von großer Bedeutung. So verwundert es nicht, daß ätherische Öle, Gewürze und natürliche Harze von alters her zur Aromatisierung von Lebensmitteln und zur Parfümierung gebraucht werden. Vor dem Hintergrund eines weltweit steigenden Bedarfs, limitierter natürlicher Ressourcen und einer hohen Akzeptanz des Verbrauchers für alles, was „natürlich“ ausgelobt ist, hat die Entwicklung objektiver Verfahren zur Authentizitätskontrolle von Duft- und Aromastoffen in den letzten Jahren starke Beachtung gefunden. Im Interesse des Verbraucherschutzes gilt es, die analytische Differenzierung zwischen natürlichen und naturidentischen Aromastoffen zu realisieren. Darüber hinaus stehen wir heute auch vor der Herausforderung, nicht nur den biogenen Ursprung, sondern auch die Naturbelassenheit eines Aromas analytisch zuverlässig zu definieren.
Approximately 18% of ‘Satsuma’ mandarins produced in the Eastern and Western Cape of South Africa are discarded because of strict export standards. The demand for natural flavourants presented an opportunity to extract a unique flavourant from ‘Satsuma’ mandarin rind for liqueur production. In this study the yield and consistency of the extraction of the flavourant was optimised against aroma intensity while maintaining a unique flavour proposition. The highest aroma intensity, minimum variability and maximum tolerable rancidity was achieved at a yield of 61 % using rind with a moisture content of 25%, an ETOH extractant concentration = 90% (v/v), a ratio of rind to extractant (m/v) ranging from 20 to 30% and a maceration period of 360 h. The valuable heart fraction was distilled between 60 to 80% ETOH content (v/v). Methyl-n-methylanthraniiate content was investigated as a biochemical marker to monitor processing quality. This parameter only accounted for 30% of the variation observed and proved unreliable. In comparing the flavour profile of the ‘Satsuma’ mandarin extract with that of the internationally renowned Mandarine Napoléon Grande Liqueur, the extract presented a unique citrus-like aroma profile that could contribute to blending a proudly South African liqueur.
As consumers demand more certainty over where their food and beverages originate from and the genuineness of ingredients, there is a need for analytical techniques that are able to provide data on issues such as traceability, authenticity, and origin of foods and beverages. One such technique that shows enormous promise in this area is gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). As will be demonstrated in this review, GC-C-IRMS is able to be applied to a wide array of foods and beverages generating data on key food components such as aroma compounds, sugars, amino acids, and carbon dioxide (in carbonated beverages). Such data can be used to determine synthetic and natural ingredients; substitution of 1 ingredient for another (such as apple for pear); the use of synthetic or organic fertilizers; and origin of foods and food ingredients, including carbon dioxide. Therefore, GC-C-IRMS is one of the most powerful techniques available to detect fraudulent, illegal, or unsafe practices in the food and beverages industries and its increasing use will ensure that consumers may have confidence in buying authentic products of known origin.
The present paper provides descriptions and critical views of the most significant chromatography-based methods, employed in the field of Citrus essential oils, mainly over the past decade. Both single-column and multidimensional chromatography approaches are reported, with advantages and shortcomings of each method reported. The contribution reports compositions only marginally. For detailed information on the latter issue, the reader is directed to two books, namely Citrus and Citrus oils, referenced in the paper. A great deal of space is devoted to the use of the mass spectrometer, in relation to its potential for separation and identification. The employment of the most powerful chromatography techniques available today, namely comprehensive two-dimensional ones, is also described. Finally, possible future scenarios in the field of Citrus essential oil analysis are anticipated. Copyright © 2011 John Wiley & Sons, Ltd.
The chemical composition of cold-pressed mandarin peel oil from Cuba was studied by GC and GC/MS. Eigthy-five compounds of the oil were identified of which limonene (78.3 %) and γ-terpinene (7.2 %) were the major constituents. The composition of the peel oil is characterized by higher percentages of monoterpene and sesquiterpene hydrocarbons and the presence of many aliphatic saturated and unsaturated aldehydes at lower concentrations.
The format of this year's Update follows that used last year¹ with some minor changes in the section headings. Although an attempt is made to consider all relevant refereed papers, conference abstracts, reports, book chapters and patents for inclusion, this review does not attempt to be comprehensive in its coverage. Critical selection is based on criteria which have been applied more strictly this year than in previous years in order to focus more sharply on the most significant developments reported during the period (approximately corresponding to 1997) covered by this Update. The prime consideration is that the reports should present advances in instrumentation and methodology or improved understanding of the fundamental processes involved in the MS process. As a general rule, conference abstracts are not included because they rarely provide sufficient information to judge whether or not they meet the criteria. We consider it better to wait for full details to appear in a refereed journal. A similar policy applies to those papers in a language other than English and unlikely to reach a wide readership.
Routine applications of atomic MS are not covered in this Update and readers are referred to the Updates on Industrial Analysis: Metals, Chemicals and Advanced Materials,² Environmental Analysis³ and Clinical and Biological Materials, Food and Beverages.⁴ An additional review that can be recommended is that of Moens⁵ on applications of MS in the analysis of biological materials. Comprehensive evaluations of MS techniques for the analysis of solid samples have been reported by Gijbels and Bogaerts⁶ and Becker et al.⁷
Papers included in this Update must be on atomic spectrometry but some areas of study introduce problems in defining atomic and molecular studies. One of the major drives in recent years has been to develop methods for speciation studies, in particular using ESMS, GC-MS or ICP-MS. The study, for example, of organic arsenic species by ICP-MS involves MS of the atomic ions but in ESMS and GC-MS the molecular species are usually detected. In general, studies of 'exotic' nuclei far from stability are excluded but the determination of radioactive elements in 'real' samples can be included. Very few measurements in SIRMS are of atomic species, yet the object of measuring natural isotopic composition is to study or use a fundamental atomic property. Such studies are included but the use of enriched spikes in tracer studies are excluded because the focus of the study is not on the atomic properties of the tracer element.
The strong progress being made in most areas of atomic MS is evident from the different sections of this Update. The various trends have been identified in each section and range from the continued improvements in sample preparation for TIMS analysis of remarkable sensitivity and precision to the demand for simpler and cheaper AMS instrumentation so that applications to biomedical research can be fully exploited. Much attention continues to be given to sample preparation and introduction for ICP-MS, in particular for speciation analysis, yet relatively little effort is being given to instrumental development. Although SIMS and SNMS are widely used techniques, fundamental problems remain for quantification and work continues on developing methodologies to optimize analyses.
The quality assessment of bergamot essential oils was established employing the gas chromatography-combustion- isotope ratio mass spectrometer (GC-C-IRMS) technique. An authenticity range was obtained investigating the carbon stable isotope ratio of genuine Italian bergamot essential oils (harvest period 2008–2009), in order to compare the GC-C-IRMS data of several industrial, commercial and foreign bergamot essential oil samples. Moreover, with the aim to test the efficiency and the sensibility of IRMS device, self-adulterated in laboratory bergamot oil samples were analyzed. The data were compared with those achieved by conventional enantioselective gas chromatography (Es-GC) and high resolution gas chromatography (GC-FID). Results of this work indicated that GC-C-IRMS was able not only to detect the presence of adulterants in the samples, but also to discriminate the bergamot oil samples according to their geographic provenance and the nature of the adulterants added.
The δ13CPDB values of characteristic flavor components of mandarin essential oils have been measured by gas chromatography/isotope ratio mass spectrometry. For genuine mandarin oils a characteristic authenticity profile was established and used for the authenticity control of commercially available mandarin oils. In addition to cold-pressed mandarin essential oils, distilled mandarin and sweet orange oils were investigated to assess blends of cold-pressed mandarin oils with these products. Keywords: GC/IRMS; δ13CPDB values; authenticity profile; authenticity control; mandarin essential oil; Citrus reticulata Blanco
Peel and leaf oils of 41 mandarin cultivars, belonging to the Citrus reticulata Blanco species, were obtained from fruits and leaves collected on mandarin trees submitted to the same pedoclimatic and cultural conditions. Their chemical composition was investigated by capillary GC, GC/MS and NMR and the results were submitted to a cluster analysis and a discriminant analysis. Two major chemotypes, limonene and limonene/γ-terpinene, were distinguished for peel oils while three major chemotypes, sabinene/linalool, linalool/γ-terpinene and methyl N-methylanthranilate, were observed for leaf oils.
The on-line coupling of gas chromatography and isotope ratio mass spectrometry via a pyrolysis interface (GC-pyrolysis-IRMS,
GC-P-IRMS) allows the simultaneous determination of δ13C and δ18O values for organic compounds. On the basis of illustrative investigations of vanillin from different origins, the scope
and limitations of the new method are discussed.
Regional origin assignment of highly valuable milk products such as butter, is of considerable importance for legal, fiscal
and trade controls within the European Union (EU). It is also of value for ensuring fair competition and as a means of protecting
consumers against fraud due to mislabelling. Conventional chemical methods of analysis are not able to determine the regional
provenance of butter unambiguously. Therefore, stable isotope ratio determinations of the light elements (C,N,O,S; bioelements)
and the heavy element, Sr (a trace element), have been used for this purpose. Stable isotope ratios of these elements in natural
cycles, their variations due to climate and geology, the abiotic and biological fractionation of isotopes and, finally, the
reasons for regional differences in multielement stable isotope ratios of butter are discussed. Results are given for butter
from several European countries and from outside the EU. The results indicate that stable isotope ratios and subsequent discriminant
analysis based on data for samples of certified origin can enable the reliable detection of the regional provenance of butter.
Mexican people employed infusion of leaves of Choisya ternata Kunth for their antispasmodic and "simulative properties".
In the present study the detailed GC and GC-MS analyses of the essential oil of Choisya ternata Kunth (Rutaceae) were performed. The presence of a minor constituent isopropyl N-methylanthranilate (1) was revealed among other identified volatiles. A synthesis of 1 was undertaken in order to corroborate this find and obtain gram quantities that would allow the testing of its biological activity (peripheral and central antinociceptive activity).
The oils were investigated by GC and GC-MS. Synthesized compounds were spectrally characterized (UV-Vis, IR, 1D and 2D NMR, MS). The obtained synthetic samples of compounds were assayed for peripheral and central antinociceptive activity in two models (effects on acetic acid induced writhing in mice and the hot plate test for nociception).
Detailed GC and GC-MS analyses of the essential oil of Choisya ternata Kunth (Rutaceae) among 157 other identified volatiles revealed the presence of a minor constituent isopropyl N-methylanthranilate (1). Compound 1, named ternanthranin, is therefore detected as a natural product for the first time with a very restricted occurrence (samples of several citrus oils were screened for the presence of 1). The antinociceptive activities were assayed for ternanthranin, the two other synthetic analogs, methyl and propyl N-methylanthranilate, as well as the essential oil and the crude ethanol extract of the leaves. The results clearly demonstrate a very high (even significant at 0.3 mg/kg) dose dependent activity for the anthranilates (and the extracts). Isopropyl N-methylanthranilate showed the highest, while methyl N-methylanthranilate showed the lowest activity (with the methyl ester at 3 mg/kg still better than acetylsalicylic acid, at 200 mg/kg, in the first, or comparable with morphine, at 5mg/kg, in the second test).
This study once again revealed that detailed investigations of plant species with ethnopharmacologically documented activity may yield new natural compounds-a new alkaloid (ternanthranin), a volatile simple anthranilate that can be considered responsible for the antinociceptive activity of the crude plant extracts.
In der vorliegenden Arbeit wurden Studien zur bakteriellen Biotransformation von N Alkyl- sowie N,N Dialkylarylaminen mit dem Ziel der arylischen Hydroxy-lierung und N-Dealkylierung durchgeführt. Bodenproben wurden einem Screening-Verfahren unterworfen, um selektiv nach Mikroorganismen zu suchen, die zu den genannten Biotransformationen fähig waren. In einem Screeningverfahren wurden unter Verwendung von N-Ethyl-N methyl-anilin als Standardsubstrat aus Boden-proben Mikroorganismen isoliert und auf ihre Fähigkeit zur Biotransformation überprüft. Einer der isolierten Stämme setzte das zugeführte Substrat effizient und reproduzierbar zu drei Hauptprodukten um. Deren Strukturaufklärung erfolgte mittels Gaschromatographie-Massenspektrometrie (GC-MS) sowie anhand ein-dimensionaler NMR-Experimente (1H-NMR und 13C-NMR). Identifiziert wurden zwei hydroxylierte Produkte, N Ethyl-N-methyl-2-aminophenol und N-Ethyl-N-methyl-4-aminophenol, ferner wurde N-Ethylanilin, das N Demethylierungsprodukt gebildet. Die Identitäten wurden durch synthetisierte Referenzsubstanzen bestätigt. Die phänotypische und genotypische Charakterisierung dieses Bodenisolates als Bacillus megaterium erfolgte mittels mikroskopischer und färbetechnischer Methoden sowie der 16S rDNA-Sequenzierung. Zur eindeutigen Zuordnung wurde eine DNA/DNA-Hybridisierung gegenüber dem Bacillus megaterium Type-strain (DSM 32, ATCC 14581t) durchgeführt. In einem erweiterten Substratscreening wurden die strukturellen Voraussetzungen zur Biotransformation von N-Alkyl- und N,N Dialkylarylaminen durch Bacillus megaterium ermittelt. Ausführlich sind Sub-stituenteneffekte in Bezug auf Hydroxylierung und N-Dealkylierung untersucht worden. Sperrige und räumlich große Substrate wie N,N,N´,N´-Tetramethyl-p,p´ benzidin als auch N,N,N´,N´-Tetramethyl-p-benzidin wurden nicht hydro-xyliert; allerdings fand bei beiden Substrate eine N-Demethylierung statt, wobei das Erstere stärker N demethyliert wurde. Der Effekt des Austausches von Stickstoff gegen Phosphor in einigen Substraten wurde ebenfalls untersucht. So kamen Dimethylphenylphosphin und Diethylphenylphosphin mit Bacillus megaterium zur Anwendung. Phosphor-haltige Substrate wurden von B. megaterium nicht umgesetzt. Durch Versuche mit verschiedenen Induktoren und Repressoren wurde die Cytochrom-P-450-Aktvität des isolierten Bacillus megaterium bei der Bio-transformation von N,N-Diethylanilin untersucht. Hierbei wurde gezeigt, dass durch bestimmte Barbiturate die arylische Hydroxylierung als auch die N Deethylierung gesteigert wurden. Repression der Hydroxylierungs- und N Dealkylierungsaktivität zeigte sich durch Metyrapon, n-Octylamin, Pyridin und Imidazol. Die von Bacillus megaterium durchgeführte N-Demethylierung von N,N Dimethylanilin sowie N-Ethyl-N-methylanilin wurde im Hinblick auf Formaldehydbildung untersucht. Dies erfolgte im Inkubationsmedium direkt in-situ, mittels Cysteamin-Zugabe in das Medium, mit Umsetzung zu Thiazolidin. Anhand von Inkubationsversuchen mit den stabil-isotopenmarkierten Substraten N,N-Di-(trideuteromethyl)-anilin und N-Ethyl-N (trideuteromethyl)-anilin sowie N,N-Di-[methyl-13C]-anilin und N-Ethyl-N [methyl-13C]-anilin wurde anhand der Massenspektren der gebildeten Thiazolidine eindeutig festgestellt, dass die Methylgruppe als Formaldehyd abgespalten wird. Das Potential von Bacillus megaterium zur N-Dealkylierung wurde zur mikrobiellen N Demethylierung von natürlichem N-Methyl-methyl-anthranilat genutzt. Dadurch wurde der natürliche Aromastoff Methylanthranilat gewonnen. Zur Optimierung der bakteriellen Biotransformation von N-Methyl-methyl-anthranilat zu Methylanthranilat wurden in Bezug auf Wachstumsmedium, Inkubationstemperatur, pH-Wert des Inkubationsmediums sowie Substrat-konzentration verschiedene Variationen durchgeführt. Die antimikrobiellen Eigenschaften von N-Methyl-methylanthranilat und Methylanthranilat gegenüber Bacillus megaterium wurden durch Hemmhofbildung sowie der Bestimmung der Inhibierungskonzentration im Flüssigmedium nachgewiesen. Sowohl Substrat als auch Produkt erwiesen sich in den unterschiedlichen Tests als antibakteriell. Im Anschluß an Versuche zur Immobilisierung, die zu geringeren Ausbeuten führten, erfolgten schließlich Umsetzungen im Bioreaktor. Hierbei ließen sich die bei den Schüttelkulturen erhaltenen Ergebnisse direkt proportional auf den Fermenter übertragen. The goal of this study was to conduct the microbial biotransformation of N-alkyl- and N,N dialkylarylamines. Main objective was the arylic hydroxylation and N-dealkylation of this class of substrates. By this, microorganisms were isolated from topsoil and a selective screening process was started to search for microorganisms capable of con-ducting the biotransformations mentioned above. In a screening process and by the use of N-ethyl-N methylaniline as substrate, microorganisms of soil samples were isolated and proven of their ability to biotransformate N-ethyl-N-methylaniline. One isolate showed three biotransformation products. Structure determination was done by gaschromatography-masspectrometry (GC-MS) and nuclear magnetic resonance experiments (1H-NMR and 13C-NMR). N-ethyl-N-methylaniline was biohydroxylated to N-ethyl-N-methylaniline-2-aminophenol and N ethyl-N-methyl-4-aminophenol, N demethylation of N-ethyl-N-methyl-aniline afforded N-ethylaniline. The soil isolate was characterized and identified phenotypical and genotypical by colour reactions and the standard 16S rDNA method being Bacillus megaterium. To complete the assignment of the isolate to the species Bacillus megaterium, DNA/DNA-hybridization analysis against the Bacillus megaterium type strain (DSM 32, ATCC 14581t) was conducted. In an extended substrate screening, structural properties for a successful bio-transformation of N-alkyl- and N,N-dialkylarylamines by Bacillus megaterium were investigated. Substituent influences were proven in a further substrate screening regarding hydroxylation as well as N-dealkylation. Bulky and large substrates like N,N,N´,N´-tetramethyl-p,p´-benzidine and N,N,N´,N´-tetramethyl-p-benzidine were not hydroxylated by the microorganisms. But, N-demethylation was observed whereas the first one was more accepted. Exchange of nitrogen against phosphorus by using dimethylphenylphosphine and diethylphenylphosphine as substrates finally stopped all biotransformation activity of Bacillus megaterium. Neither arylic hydroxylation nor P dealkylation occurred. Trials to influence the bacterial activity towards the substrate N,N-diethylaniline, elicitors and inhibitors were used to affect cytochrome-P-450. Certain barbiturates clearly increased arylic hydroxylation as well as N dealkylation. Repression of these metabolites was shown by metyrapone, pyridine, n-octylamine and imidazole. N-demethylation reaction of Bacillus megaterium was further investigated for a detection of formaldehyde. Formaldehyde, built after N-demethylation of N,N dimethylaniline or N ethyl-N-methylaniline, was caught by added cysteamine and derivatized to thiazolidine. Incubation of the stable isotope labelled substrates N,N-di-(trideuteromethyl)-aniline and N-ethyl-N-(trideuteromethyl)-aniline as well as N,N-di[methyl 13C]-aniline and N-ethyl-N-[methyl-13C]-aniline and the resulting mass spectral fragmentations of the build labelled thiazolidines clearly stated that formaldehyde comes from methylgroups. Observed N-dealkylation reactions of Bacillus megaterium were used to produce the food flavour methyl anthranilate by microbial N-demethylation of N methyl methyl anthranilate. Several variations of the standard conditions were proven for the optimization of the bacterial biotransformation from N-methyl methyl anthranilate to methyl anthranilate: incubation temperature, pH-value, substrate concentration and media. Antimicrobial activities of N-methyl methyl anthranilate and methyl anthranilate against Bacillus megaterium were tested by using the paper disc diffusion assay and determination of the minimum inhibitory concentration in liquid medium. Substrate as well as product exhibited antimicrobial activity in both tests. To improve the stability of Bacillus megaterium, bacterial cells were immobilized in sodium-alginate-globules resulting in very low yields of methyl anthranilate. Finally, as a summarization of all obtained methyl anthranilate results, an upscaling was done in the bioreactor in a direct proportional way.
An inter-laboratory exercise was carried out by a consortium of five European laboratories to establish a set of compounds, suitable for calibrating gas chromatography/combustion/isotope ratio mass spectrometry (GC-C-IRMS) devices, to be used as isotopic reference materials for hydrogen, carbon, nitrogen and oxygen stable isotope measurements. The set of compounds was chosen with the aim of developing a mixture of reference materials to be used in analytical protocols to check for food and beverage authentication. The exercise was organized in several steps to achieve the certification level: the first step consisted of the a priori selection of chemical compounds on the basis of the scientific literature and successive GC tests to set the analytical conditions for each single compound and the mixture. After elimination of the compounds that turned out to be unsuitable in a multi-compound mixture, some additional oxygen- and nitrogen-containing substances were added to complete the range of calibration isotopes. The results of delta(13)C determinations for the entire set of reference compounds have previously been published, while the deltaD and delta(18)O determinations were unsuccessful and after statistical analysis of the data the results did not reach the level required for certification. In the present paper we present the results of an inter-laboratory exercise to identify and test the set of nitrogen-containing compounds present in the mixture developed for use as reference materials for the validation of GC-C-IRMS analyses in individual laboratories.
Compound-specific isotope analysis (CSIA) by isotope ratio mass spectrometry (IRMS) following on-line combustion (C) of compounds separated by gas chromatography (GC) is a relatively young analytical method. Due to its ability to measure isotope distribution at natural abundance level with great accuracy and high precision, GC-C-IRMS has increasingly become the method of choice in authenticity control of foodstuffs and determination of origin in archaeology, geochemistry, and environmental chemistry. In combination with stable isotope labelled compounds, GC-C-IRMS is also used more and more in biochemical and biomedical application as it offers a reliable and risk-free alternative to the use of radioactive tracers. The literature on these topics is reviewed from the advent of commercial GC-C-IRMS systems in 1990 up to the beginning of 1998. Demands on sample preparation and quality of GC separation for GC-C-IRMS are discussed also.
The isotope ratios of monoterpene hydrocarbons in Citrus junos Tanaka (yuzu) essential oils from different origins were determined by ordinary high-resolution gas chromatography-mass spectrometry (HRGC-MS). Both intensities of the molecular mass peaks (m/z 136) and of the isotope peaks (m/z 137) of monoterpene hydrocarbons were measured by single-ion monitoring with an MS analysis. The isotope ratios (m/z 137/136) of the ten monoterpene hydrocarbons commonly contained in citrus essential oils, alpha-pinene, beta-pinene, sabinene, myrcene, alpha-phellandrene, alpha-terpinene, limonene, gamma-terpinene, beta-phellandrene and terpinolene, were determined in yuzu samples of the highest commercial quality from 42 different production districts. Statistical treatment of these data by the t-test and sign test revealed significant differences of the isotope effects in each yuzu sample. It is suggested that this technique will be applicable for evaluating the quality, genuineness and origin of citrus fruits and their products. The isotope fingerprints were also demonstrated in several citrus fruits other than the yuzu samples.
The bulk delta 15 N-value of plant (leaf) biomass is determined by that of the inorganic primary nitrogen sources NO(3)(-), NH(4)(+) and N(2), and by isotope discriminations on their uptake or assimilation. NH(4)(+) from these is transferred into "organic N" mainly by the glutamine synthetase reaction. The involved kinetic nitrogen isotope effect does not become manifest, because the turnover is quantitative. From the product glutamine any further conversion proceeds in a "closed system", where kinetic isotope effects become only efficient in connection with metabolic branching. The central and most important corresponding process is the GOGAT-reaction, involved in the de novo nitrogen binding and in recycling processes like the phenylpropanoid biosynthesis and photorespiration. The reaction yields relatively 15N-depleted glutamate and remaining glutamine, source of 15N-enriched amide-N in heteroaromatic compounds. Glutamate provides nitrogen for all amino acids and some other compounds with different 15N-abundances. An isotope equilibration is not connected to transamination; the relative delta 15 N-value of individual amino acids is determined by their metabolic tasks. Relative to the bulk delta 15 N-value of the plant cell, proteins are generally 15N-enriched, secondary products like chlorophyll, lipids, amino sugars and alkaloids are depleted in 15N. Global delta 15 N-values and 15N-patterns of compounds with several N-atoms can be calculated from those of their precursors and isotope discriminations in their biosyntheses.
The isotope ratio of monoterpene hydrocarbons in citrus essential oils of different origins was measured by ordinary high-resolution gas chromatography-mass spectrometry (HRGC-MS). The isotope ratio (Ir) was determined by the ratio of the isotope peak intensity (m/z 137) to the molecular mass peak intensity (m/z 136) of the monoterpene hydrocarbons. The accuracy of Ir was examined by measuring monoterpene hydrocarbon standards and 13C-labeled compounds. The isotope fingerprints based on the values of monoterpene hydrocarbons from lemon, lime and yuzu essential oils were determined. These citrus essential oils were also discriminated by a principal component analysis of their Ir data. The characteristic vectors showed that alpha-terpinene, beta-pinene and beta-phellandrene were important components for distinguishing between the citrus species. It is suggested that this technique will be applicable to evaluate the quality, genuineness and origin of citrus fruits and their products.
The aim of this work was to develop a method for authenticity control of organically grown orange fruits. Due to the different kinds of nitrogen fertilization of the soil in organically and conventionally managed farms, the study tried to verify the possibility to differentiate Navelina and Tarocco orange fruits obtained by these production systems through the detection of markers linked to nitrogen metabolism. In addition to the classic quality parameters, total nitrogen (N) and synephrine contents in juice and (15)N/(14)N isotope ratio (expressed as delta(15)N per thousand) in proteins of pulp and amino acids of juice were determined. The results obtained indicated that total N and synephrine contents were significantly higher in conventional fruits, whereas the delta(15)N per thousand values were higher in the organic ones. The new markers identified in this research by linear discriminant analysis of the data may constitute a useful tool to differentiate organic citrus fruits or juices from conventional ones.
Solid-phase microextraction (SPME) coupled to gas chromatography/isotope ratio mass spectrometry was used to determine the delta15N and delta13C signatures of selected nitroaromatic contaminants such as the explosive 2,4,6-trinitrotoluene (TNT) for derivation of isotopic enrichment factors of contaminant transformation. Parameters for efficient extraction of nitroaromatic compounds (NACs) and substituted anilines from water samples were evaluated by SPME-GC/MS. delta13C signatures determined by SPME-GC/IRMS and elemental analyzer IRMS (EA-IRMS) were in good agreement, generally within +/-0.7 per thousand, except for 2,4-dinitrotoluene (2,4-DNT) and TNT, which showed slight deviations (<1.3 per thousand). Limits of detection (LODs) for delta13C analysis by SPME-GC/IRMS were between 73 and 780 microg L-1 and correlated with the extraction efficiencies of the compounds determined by SPME-GC/MS. Nitrogen isotope measurements by SPME-GC/IRMS were of similar precision (standard deviations <0.8 per thousand) for all NACs except for TNT. delta15N signatures matched the reference values obtained by EA-IRMS within +/-1.3 per thousand (+2.5 per thousand for TNT), but no systematic trend was found for the deviations. LODs of delta15N measurements ranged from 1.6 to 9.6 mg L-1 for nitrotoluenes, chlorinated NACs and DNTs (22 mg L-1 for TNT). The SPME-GC/IRMS method is well suited for the determination of isotopic enrichment factors of various NAC transformation processes and provides so far unexplored possibilities to elucidate behavior and degradation mechanisms of nitroaromatic contaminants in soils and groundwaters.
Authenticity of bergamot oil is established using enantioselective capillary gas chromatography as well as isotope ratio mass spectrometry (IRMS) online coupled with capillary gas chromatography as alternative methods of origin specific analysis. Enantiomeric ratios, isotopic data, as well as quantification of bergamot oil compounds are evaluated integrally. Scope and limitations of the techniques are discussed.
Enantioselective capillary gas chromatography, as well as isotope ratio mass spectrometry (IRMS), online coupled with capillary gas chromatography are used in the origin specific analysis and authenticity control of balm oil compounds. Scope and limitations of the methods are discussed.
A rapid method to detect the addition of reconstituted mandarin oils to natural mandarin essential oils is suggested. The method is based on the ratio of the two enantiomers of limonene determined by GC using an on-line coupling of non-chiral and chiral capillary columns. The ratio of (−)-limonene and (+)-limonene in the genuine mandarin oils was 2.2 to 97.8, while in reconstituted oils the same ratio was 13.4 to 86.6. Addition of reconstituted oils increases the ratio of (--) to (+)-limonene in genuine oils enabling the detection of additions of even 5% of reconstituted oils to genuine mandarin oils.
Summary With regard to the analytical differentiation between naturally grown fermentatively produced and synthetic (nature-identical) arome compounds by GC-C-IRMS, simple and practicable methods without any isotope fractionation are essential for efficient enrichment of minor flavour compounds from citrus oils. Octanal, nonanal, decanal, dodecanal, neral and geranial from different orange oils and commercially available products, labelled “natural” or “nature-identical” have been investigated. The13C/12C ratios were evaluated in a narrow range of variation and allowed the differentiation of synthetic nonanal, decanal and dodecanal from their natural analogues.
RECENT international efforts to conserve the African elephant Loxodonta africana prompted us to seek an appropriate method for determining the area from which individual tusks were derived. Trace element analysis of ivory has indicated the potential of chemical analysis for source identification1, but recent isotopic studies of African mammals2–5 suggest another approach. Stable carbon isotope ratios (13C/12C) in elephant bone collagen clearly reflect the mixture of C3 foliage and C>4 grasses in the diet, and are directly proportional to the density of C3 browse2. Furthermore, nitrogen isotope ratios (15N/14N) in bone collagen of African mammals are related to rainfall or water stress3–5. Strontium isotopes (87Sr/86Sr) in bone or ivory can be expected to reflect local geology6,7. Here we report on a study of ivory and bone samples from different regions of Africa demonstrating the feasibility of trivariate isotopic analysis to identify the area in which an elephant lived, thus providing a potentially powerful tool for the control of illegal trading in ivory.
Research based on 15N stable isotope variations in natural compounds is expanding in scientific fields such as biogeochemistry (isotope fractionation effects measurements1–7), metabolic studies8,9, hydrology (research of NO3
− pollution origin in aquifers10–14), agronomy (estimate of N2 symbiotic fixation by legumes15–17) and oceanography (determination of the source of sedimentary nitrogen18–21). However, intercomparison of results obtained in different laboratories is a problem due to the lack of intercalibrated standards. Atmospheric nitrogen has been chosen by many investigators as a standard20,22,23 and I present here a simple method for the preparation of atmospheric N2 as a standard for δ
15N expression with excellent reproducibility. The results indicate a wide homogeneity in isotopic composition of atmospheric nitrogen which appears to be a reliable standard for 15N natural abundance measurements.
Development of the technique of isotope-ratio-monitoring has been focused on implementing the measurement of of GC eluates (compound-specific isotope analysis). This technique has now been successfully extended to the measurement of in volatile nitrogen-bearing organic compounds and of in water. Precise and accurate measurements of (±0.4%) at natural abundance have been made on nanogram quantities of a variety of nitrogen-containing compounds. Nitrogen is quantitatively converted to N2 in a novel post-GC interface which incorporates a micro-oxidation reactor (for oxidizing organic compounds eluting from the GC), a reduction reactor (for conversion of NOx to N2) and CO2 removal from the carrier gas stream; the N2 is isotopically characterized in a high sensitivity gas isotope mass spectrometer (Finnigan MAT 252). For analysis, sub-microliter amounts of water were reacted with carbon to produce CO and H2 (Unterzaucher reaction) in a high temperature micro-furnace. The effluent of the micro-furnace is introduced into a gas isotope mass spectrometer (Finnigan MAT Deltas-S) using an open split coupling. The isotope ratios are measured by simultaneous monitoring of the CO+ ion currents at m/z = 28 and 30. Systematic experiments show that, while synthetic diamond is initially a better reaction substrate than either graphite or natural diamond, progressive graphitization of the diamond grains leads to a gradual increase in memory.
Data are presented which establish the reproducibility of 15N:14N mass spectrometer ratio measurements at approximately +/- 1 unit of 816N, the per mill 16N enrichment. This degree of reproducibility has been obtained even when the concentration of large volumes of water is required or with nitrogen derived from soil samples. The procedures we follow to achieve this precision are also detailed. A series of shelf chemicals had a range of values of 816N, probably reflecting isotopic fractionation during their manufacture. Commercial fertilizers had values of 816N close to zero and uniformly lower than sources of nitrogen of recent biological origin. While the 816N value of the products of the mobilization of soil N (i.e., NH4+ and NO2-) will probably most often be of interest rather than the values of the total nitrogen, some values of the latter are reported. The 816N of the total nitrogen of soils sampled near Cerro Gordo in the Illinois Corn Belt had values higher than the common commercial fertilizers. Some soils sampled in other locations had significantly lower values than those found in central Illinois.
(C) Williams & Wilkins 1974. All Rights Reserved.
The essential oils of 10 authentic coriander samples of different origin were analyzed. Capillary gas chromatography, on-line coupled with isotope ratio mass spectrometry (cGC-IRMS) using Stabilwax as the stationary phase, was applied. Alternatively, heptaxis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin in PS 268 was used as the chiral stationary phase. The enantiomeric ratio and the delta(13)C(PDB) values of some characteristic-compounds were compared with those of commercially available spices and essential oils. The influence of isotopic effects on the delta values during the primary CO2 fixation was eliminated by definition of a suitable internal isotopic standard (i-IST). The isotopic effects among genuine monoterpenes are, therefore, exclusively determined by the influence of enzymatic reactions during secondary biogenetic pathways.
Plants with the C3, C4, and crassulacean acid metabolism (CAM) photosynthetic pathways show characteristically different discriminations against 13C during photosynthesis. For each photosynthetic type, no more than slight variations are observed within or among species. CAM plants show large variations in isotope fractionation with temperature, but other plants do not. Different plant organs, subcellular fractions and metabolises can show widely varying isotopic compositions. The isotopic composition of respired carbon is often different from that of plant carbon, but it is not currently possible to describe this effect in detail. The principal components which will affect the overall isotope discrimination during photosynthesis are diffusion of CO2, interconversion of CO2 and HCO−3, incorporation of CO2 by phosphoenolpyruvate carboxylase or ribulose bisphosphate carboxylase, and respiration. Theisotope fractionations associated with these processes are summarized. Mathematical models are presented which permit prediction of the overall isotope discrimination in terms of these components. These models also permit a correlation of isotope fractionations with internal CO2 concentrations. Analysis of existing data in terms of these models reveals that CO2 incorporation in C3 plants is limited principally by ribulose bisphosphate carboxylase, but CO2 diffusion also contributes. In C4 plants, carbon fixation is principally limited by the rate of CO2 diffusion into the leaf. There is probably a small fractionation in C4 plants due to ribulose bisphosphate carboxylase.
Two varieties (Nihonbare and Koshihikari) of rice plants (Oryza sativa L.) were grown hydro-ponically with two levels (20 and 100 mg N liter -1) of ammonia. Variations in levels of natural abundance of 15N (δ15N) were analyzed in the ammonia and organic nitrogen of shoots and roots, as well as in the ammonia in the culture solution. There was substantial fractionation of nitrogen isotopes during the uptake of ammonia. When plants absorbed a large proportion of ammonia from a solution with a low concentration, less negative δ15N values in plants and high positive δ15N values in the ammonia remaining in solution were observed. The reverse was found when a smaller fraction of ammonia was absorbed from a solution with a higher concentration of ammonia. The δl5N values of ammonia in shoots and roots were higher than in the respective constituent organic nitrogen, suggesting the fractionation of nitrogen isotopes during the assimilation of ammonia. Wild-type and mutant cells of the cyanobacterium (blue-green alga) Synechococcus PCC 7942 were grown in nitrate- or ammonia-containing medium as the source of nitrogen. Fractionation of nitrogen isotopes during the uptake of nitrate was limited, whereas that during the uptake of ammonia was considerable.
The δ15N-value has often tentatively been used for the assignment of nitrate to its origin. However, the very complex correlations between the different nitrogen pools, mostly accompanied by isotope discriminations, oppose a very limited application of this method. On the other hand, the oxygen isotope abundance should be more indicative, because industrially produced NO−3 must nearly exclusively contain oxygen from O2 (δ18O = +23.5%.), while NO−3 originating from a nitrification process must have water (δ18O ≅ -10%.) as the main oxygen source.For the proof of this reflection a method for the precise oxygen isotope analysis of NO−3 was developed. Its application to the δ-value determination of commercial fertilizers and NO−3 formed by nitrification absolutely confirmed the above predictions. Similarly, the isotope abundance of NO−3-samples from ground and drinking water of known origin corresponded to the expected values. On the basis of these results and taking into account the known isotope abundance shifts due to isotope effects of nitrification and denitrification, a diagram between δ15N- and δ18O-values for NO−3 was developed, which permitted the assignment of NO−3 in unknown water samples to its probable source and origin.
The combination of the relative abundances of carbon and nitrogen isotopes (13C- and 15N-values) in fruit juice pulps led to characteristic clusters, on the basis of which regional origin assignments of citrus juices were possible, which would not have been attained on the basis of only one of these parameters. Thus, while the 13C-values of juice pulps from Italy partially overlapped with those from Brazil, the 15N-values permitted an origin assignment. First attempts to extend this multi-isotope analysis to a multi-compound15N analysis, by correlating the 15N-values of fruit juice pulps to those of free amino acids, were promising. The results obtained were in line with general observation on15N abundances and biochemical correlations of secondary plant products.
Der Gehalt an stabilen and natrlichen radioaktiven Isotopen in Lebensmitteln ist oft typisch fr deren Herkunft and Verarbeitung. Anhand eines ordnenden berblicks der Resultate aus den letzten zehn Jahren werden die Mglichkeiten entsprechender Messungen aufgezeigt. Die groe Mehrzahl dieser Untersuchungen befat sich mit der13C-Analyse und betrifft vor allem die Produkte Zucker, Honig, Sirupe, Essig, Alkohol und Spirituosen. Darber hinaus finden sich eine Reihe von Daten ber Bier, Fette, le, Fleisch, Molkereiprodukte, Eier and einige Hilfs- und Zusatzstoffe. Die wichtigste Unterscheidungsmglichkeit besteht in der Zuordnung von Produkten aus Mais und/oder Zuckerrohr (schwere Pflanzen oder C4-Pflanzen) bzw. Produkten aus den iibrigen wichtigen Kulturpflanzen (leichte Pflanzen oder C3-Pflanzen). Streubreiten and Nachweisgrenzen sowie knftige Mglichkeiten, vor allem die Messung von Stickstoff-und Schwefelisotopen, werden diskutiert.The content of stable and naturally radioactive isotopes in food is often typical of its origin and manufacturing. On the basis of a classifying review of results from the last decade the possibilities of corresponding measurements are demonstrated. The majority of these studies deals with13C analysis and mainly concerns products as sugar, honey, sirup, vinegar, ethanol, and spirituous liquors. Furthermore data on beer, oils, fats, meats, dairy products, eggs, and some additives and aids are presented. The most important application is the differentiation between products originating from maize and/or sugar cane (heavy plants or C4 plants) and products from the other major cultivated plants (light plants or C3 plants). Standard deviations and detection limits as well as future possibilities, mainly concerning the determination of nitrogen and sulfur isotopes are discussed.
The
13CPDB values of nine flavour compounds from five different lemon oils were determined using gas chromatography-isotope ratio mass spectrometry. By definition of a suitable internal isotopic standard (i-IST), the influence of CO2 fixation during photosynthesis is eliminated. The isotopic effects among genuine monoterpenes are, therefore, limited to the influence of enzymatic reactions during secondary biogenetic pathways. Calculating versus nerylacetate as an i-IST yields fruit-specific (
13C values for neral and geranial with low standard deviation and seems to be suitable for authenticity control of lemon oils.Die
13CPDB-Werte von neun Aromakomponenten aus fnf unterschiedlichen Zitronenlen werden mittels GC-IRMS bestimmt. Durch die Wahl eines internen Isotopenstandards (i-IST) werden Isotopeneffekte whrend der CO2-Fixierung (in der Photosynthese) eliminiert und die zwischen den einzelnen Substanzen auftretenden Unterschiede im13C/12C-Verhltnis auf enzymatische Einflsse des Sekundrstoffwechsels begrenzt. Mit Nerylacetat als i-IST lassen sich fruchtspezifische
13C-Werte von Neral bzw. Geranial mit hoher Genauigkeit bestimmen und zur Authentizittskontrolle von Zitronenlen heranziehen.
Secondary plant products Compound-specific isotope analysis: extending toward Fry, B. Stable isotope diagrams of freshwater food webs
- E A Bell
- B V Charlwoods
Bell, E. A.; Charlwoods, B. V. Secondary plant products. In Enziklopedia of Plant Physiologie; Springer-Verlag: Berlin, 1980; p 145. Brand, W. A.; Tegtmeyer, A. R.; Hilkert, A. Compound-specific isotope analysis: extending toward Fry, B. Stable isotope diagrams of freshwater food webs. Ecology 1991, 72, 2293-2297.
Information on mandarin peel oil
- E Kugler
- E Kovats
Kugler, E.; Kovats, E. Information on mandarin peel oil. Helv. Chim. Acta 1963, 46, 1480-1513.
Nitrogen-15 in the natural environment In Hand-book of Environmental Isotope Geochemistry
- R Lé
Lé, R. Nitrogen-15 in the natural environment. In Hand-book of Environmental Isotope Geochemistry; Fritz, P., Fontes, J. C., Eds.; Elsevier: Amsterdam, 1980; Vol. 10, pp 407-433.
Carbon isotope fractionation in plants. Phy-tochemistry
- O Leary
O'Leary, M. H. Carbon isotope fractionation in plants. Phy-tochemistry 1981, 20, 553-567.