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See detailUse of GC-MS in SIM-Scan mode for a selective quantification of polluting volatile organic compounds (VOC) in food industries
Eloundou Mballa, Pierre ULg; DETHIER, Bérénice ULg; Fauconnier, Marie-Laure ULg

Poster (2014, February 07)

The control of atmospheric emission discharges by food industries is classically achieved in two phases. The first one consists of sampling the target atmosphere followed by concentrating the volatile ... [more ▼]

The control of atmospheric emission discharges by food industries is classically achieved in two phases. The first one consists of sampling the target atmosphere followed by concentrating the volatile organic compounds (VOC) contained in a defined volume of this atmosphere on an adsorbing agent. These compounds are then thermally desorbed (TD) or desorbed with a solvent. In the second phase, the gas phase chromatogram (GC) will be coupled with mass spectrometry (MS) or flame ionization detector (FID) for compounds analysis. Quantitative analysis are usually achieved with solvent desorption followed by GC-FID. However, this mode imposes the dilution of the sample by a solvent and consequently may cause high detection thresholds as well as important matrix effect and possible interferences due to chemical reactions between analytes and the solvent. Besides, a preliminary qualitative analysis (GC-MS identification) is necessary. Combining TD-GC-MS allows very low detection thresholds to be reached, and the matrix effect and the interferences caused by products of the reactions between analytes and the solvent to be eliminated. The use of this combination in selected ion monitoring (SIM) mode allows targeting analytes via their characteristic ions, increasing their sensitivity and repeatability insuring more accuracy for simultaneous qualitative and quantitative analysis. This technique was experimented for seeking VOC in the atmosphere around food industries. [less ▲]

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See detailContribution to the study of alliinase, the active principle of garlic
DETHIER, Bérénice ULg; Ponchaux, Julien; Laloux, Morgan et al

Poster (2014, February 07)

Alliinase is a crucial enzyme in the Allium genus. The conversion of its substrates, cysteine sulfoxides, into volatile thiosulfinates is an important mechanism in the defence of the plant. It also ... [more ▼]

Alliinase is a crucial enzyme in the Allium genus. The conversion of its substrates, cysteine sulfoxides, into volatile thiosulfinates is an important mechanism in the defence of the plant. It also provides the typical pungent flavour of garlic. As a matter of fact, the thiosulfinates decompose in a range of organosulfur compounds (OSC) known for their biological activities (antioxidant, anticancer, anti-diabetes properties, etc.). The environment of the decomposition of the thiosulfinates determines the type and amount of products released. A deeper knowledge of the conditions that form each OSC could help us in the preparation of garlic-based nutraceutics in the perspective of healthier food consumption. This study aims to improve the extraction and purification the enzyme alliinase in order to perform the reaction between the enzyme and its substrates and assess the potentialities of garlic preparations. Three methods have been applied to evaluate the efficiency of the extractions and purifications of the enzyme. A first idea of the purity of the enzyme is given by an electrophoresis separation of each sample on a polyacrylamide gel (SDS-PAGE). The protein content is then measured by UV-vis spectrometry with Lowry-Folin reagent for the coloration and BSA as an external standard. Finally, the specific activity is assessed by an indirect measure of the pyruvate (released as a co-product): the addition of NADH and lactate dehydrogenase turns the pyruvate in lactate, and the disappearance of NADH is measured by UV-vis spectrometry at 340 nm. The extraction of the enzyme from garlic was performed either by PEG 8000 precipitation or by ammonium sulphate precipitation. Two purifications were tested: affinity chromatography (on ConA) and size-exclusion chromatography. The combination of the ammonium sulphate process with the ConA chromatography provided the purest enzyme, with the best activity but a lower yield than the size-exclusion process. Finally the stability of the enzyme has been assessed at 4, -20 and -80 °C, showing that the enzyme could be kept at -80 °C for over 4 months without deterioration, while activity loss was observed at higher temperature. [less ▲]

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See detailLa chimie de l'odorat
DETHIER, Bérénice ULg

Scientific conference (2013, November)

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See detailOptimization of the formation of vinyldithiins, therapeutic compounds from garlic
DETHIER, Bérénice ULg; Hanon, Emilien; Maayoufi, Said et al

in European Food Research & Technology (2013), 237(1), 83-88

Allyl sulfides, ajoenes and vinyldithiins are the three main groups of volatile organosulfur compounds that are formed when garlic is crushed. The manner garlic is processed (nature of the extraction ... [more ▼]

Allyl sulfides, ajoenes and vinyldithiins are the three main groups of volatile organosulfur compounds that are formed when garlic is crushed. The manner garlic is processed (nature of the extraction medium, temperature…) has a major influence on their relative proportion and the amounts produced. It has been proven recently that the vinyldithiins are at the origin of garlic’s capacity to prevent adipocytes development. Their incorporation in garlic-based nutraceuticals is thus particularly interesting. In this context, this work aims to optimize the production of vinyldithiins from garlic. After having determined the best garlic origin (Spanish) and the best oil for the extraction (olive or sunflower oil), the extraction conditions were optimized (1/2 (w/w garlic oil), 37 °C, 6 h) and 133 mg of vinyldithiins was obtained from 100 g of fresh garlic. Carrying out the extraction under microwave irradiation allowed increasing the yield 3.6-fold (yield 486 mg of vinyldithiins from 100 g of fresh garlic). This study may also contribute to the development of new garlic derived high value products by enhancing the comprehension of their formation. [less ▲]

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See detail(Bio)synthesis, extraction and purification of garlic derivatives showing therapeutic properties
DETHIER, Bérénice ULg; Nott, Katherine ULg; Fauconnier, Marie-Laure ULg

in Smagghe, Guy; Boeckx, Pascal; Bossier, Peter (Eds.) et al Communications in Agricultural and Applied Biosciences 2013 (2013)

Garlic has been used worldwide for centuries for its taste but also for its health benefits. Garlic's therapeutic compounds are mostly organosulfur compounds, recognized for their antioxidant, anticancer ... [more ▼]

Garlic has been used worldwide for centuries for its taste but also for its health benefits. Garlic's therapeutic compounds are mostly organosulfur compounds, recognized for their antioxidant, anticancer, anti-inflammatory and antimicrobial activity and their effect on cardiovascular diseases (reviewed by Block, 2010). When the cloves are crushed, allicin is synthesized as the vacuolar enzyme alliinase meets its substrate, the cytoplasmic alliin. Allicin is unstable and undergoes rearrangements to form three main groups of derivatives: allyl sulfides, ajoenes and vinyldithiins. The garlic processing method has a major influence on the products released both in terms of chemical composition and yields. For example, the type of medium (aqueous or oily) and the temperature can favour the formation of specific compounds. Our work aims at studying the influence of - the garlic origin, - the reaction conditions and - the extraction procedures (solvent, microwaves) on the organosulfur compounds formed. Particular attention is given to the stereochemistry and the stability of the compounds. Better understanding of the formation of high value natural molecules is important in order to lead further studies on the biological activity of the compounds or to use them as nutraceuticals. [less ▲]

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See detailAnalysis of the diastereoisomers of alliin by HPLC
DETHIER, Bérénice ULg; Laloux, Morgan ULg; Hanon, Emilien et al

in Talanta (2012), 101

Garlic has been known for its therapeutic effects for centuries and is used worldwide as a functional food. The concentration of the active molecules could be enhanced by a better knowledge of their ... [more ▼]

Garlic has been known for its therapeutic effects for centuries and is used worldwide as a functional food. The concentration of the active molecules could be enhanced by a better knowledge of their biosynthesis. The precursor of these compounds, alliin (a sulfur amino-acid) has been obtained by chemical synthesis. However, this synthesis route also leads to a diastereoisomer as co-product. This work describes the development of an analytical method which allows the separation and quantification of the two diastereoisomers in order to determine in which proportion the natural form can be produced. The HPLC method which was optimized and validated by accuracy profile exploits an original stationary phase consisting of porous graphitic carbon (PGC). Furthermore, the developped method was used to separate the diastereoisomers of methiin, another garlic cysteine sulfoxide, and to analyse and aqueous extract of garlic. The ability to quantify the amount of natural alliin is valuable for further work on garlic molecules and their application for health protection. [less ▲]

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See detailTherapeutic compounds in garlic oil: production and evolution after preparation
DETHIER, Bérénice ULg; Fauconnier, Marie-Laure ULg

Poster (2012, November 15)

Allyl sulfides, the main constituents of garlic oil, have been studied in the past decades for their effects against cancer. Since cancers are not all healed, ways to prevent it, especially with natural ... [more ▼]

Allyl sulfides, the main constituents of garlic oil, have been studied in the past decades for their effects against cancer. Since cancers are not all healed, ways to prevent it, especially with natural products that could be included in food preparation, are more than welcome. The synthesis and separation of allyl sulfides can provide larger amount of allyl sulfide than the extraction in order to make biological tests. Furthermore, the improvement of the synthesis conditions helps the understanding of the formation of allyl sulfide while garlic is processed. Finally, the study of the products allows a deeper understanding of the conversion between the allyl sulfides. A parallel can then be done with the conservation conditions of garlic-based products. The first part of this work describes the synthesis optimization using the design of experiment. The reaction of allyl bromide and sodium disulfide was carried under different conditions: the reaction duration, the heating (in microwave oven or in oil bath, at different temperature), the presence of catalyst, and the agitation were assessed. In the second part of the study, extractions are performed on garlic. The composition of the extracts is followed during time under the conditions established in the first part. The results give an optimized way to synthesize allyl sulfides, as much as an idea of the reactions happening on them in garlic preparations under various conditions. [less ▲]

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See detailOptimization of the formation of vinyldithiins, a therapeutic compound from garlic
DETHIER, Bérénice ULg; Hanon, Emilien; Fauconnier, Marie-Laure ULg

in Pulkrabova, Jana; Tomaniova, Monika; Godulova, Vanda (Eds.) et al Chemical reactions in food: book of abstracts (2012, November 14)

Garlic has been used worldwide for centuries for its taste, but also for its health benefits. The therapeutic compounds are mostly organosulfurs, and can be formed when an enzyme, alliinase, gets in ... [more ▼]

Garlic has been used worldwide for centuries for its taste, but also for its health benefits. The therapeutic compounds are mostly organosulfurs, and can be formed when an enzyme, alliinase, gets in contact with its substrate, alliin. Both are separated in an entire cell, and react when the plant is damaged. The product of the enzymatic reaction, allicin, turns quickly into different molecules with potential beneficial effects. The way garlic is processed has a major influence on the released products. Indeed, an aqueous or oily medium, as far as the temperature, can emphasize the formation of specific compounds. Vinyldithiins are one of the active molecules, and are part of the garlic’s organoleptic properties. Their effects against obesity have been recently proven. This study aims to describe the conditions of vinyldithiins formation, as well as its extraction, purification and analyse. Vinyldithiins are mostly produced when garlic is crushed in edible oil, at low temperature. Extraction conditions (garlic/oil ratio, oil and garlic source, temperature and extraction time) were optimized. Analysis of the results were performed by HPLC.Finally, a purification process was set up. These results allow better knowledges on vinyldithiins formation that can be applied in garlic-based nutraceuticals. They might also lead to new uses of garlic in the production of highly valuable compounds. [less ▲]

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See detailA new HPLC method to quantify alliin, the major sulfur compound in garlic
DETHIER, Bérénice ULg; Laloux, Morgan ULg; Hanon, Emilien et al

Poster (2012, February 10)

Garlic is recognized for centuries for its health benefits, mostly linked to its sulfur- components. Among the products extracted from the cloves, alliin retained our attention. Alliin was synthesized ... [more ▼]

Garlic is recognized for centuries for its health benefits, mostly linked to its sulfur- components. Among the products extracted from the cloves, alliin retained our attention. Alliin was synthesized. This process leads to two stereoisomers. Their HPLC separation was the aim of this work. The method described in the literature (amino column, detection at 210 nm) showed a resolution of 1,1 between the isomers. A second method was developed: the stationary phase was porous graphitic carbon and a water-ACN gradient was used for the elution. It provided a resolution of 3,2, was shorter and underwent the validation process. The method leads to satisfying results. The separation is excellent, and the validation criteria are fulfilled. This may be valuable for future research on garlic. [less ▲]

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See detailDiallyl disulfides: comparison between classical and microwave assisted synthesis
DETHIER, Bérénice ULg; Richel, Aurore ULg; Laurent, Pascal ULg et al

Poster (2011, June)

Garlic contains organosulfur compounds, such as diallyl disulfides (DADS), diallyl monosulfides (DAMS) and diallyl trisulfides (DATS), which have potential health properties. The first objective of this ... [more ▼]

Garlic contains organosulfur compounds, such as diallyl disulfides (DADS), diallyl monosulfides (DAMS) and diallyl trisulfides (DATS), which have potential health properties. The first objective of this work is to conduct the synthesis of these molecules by heating in a classical oil bath or by microwave irradiation with a phase transfer catalyst. We concluded that the synthesis should be cnducted at 40°C in an oil bath, with a phase transfer catalyst. [less ▲]

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See detailDiallyl disulfides: comparison between classical and microwave-assisted synthesis
DETHIER, Bérénice ULg; Richel, Aurore ULg; Laurent, Pascal ULg et al

in Ioannou, Efstathia; Roussis, Vassilios (Eds.) Trends in Natural Products Research: Abstracts of the Phytochemical Society of Europe (2011)

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See detailContribution à l'étude de l'alliine de l'ail
DETHIER, Bérénice ULg

Master's dissertation (2010)

Dans un contexte où l’obésité est un problème de plus en plus alarmant, l’élaboration de moyens de lutte contre celle-ci représente un défi important. Le développement des adipocytes, cellules stockant la ... [more ▼]

Dans un contexte où l’obésité est un problème de plus en plus alarmant, l’élaboration de moyens de lutte contre celle-ci représente un défi important. Le développement des adipocytes, cellules stockant la masse graisseuse du corps, peut être entravé par une molécule, la 1,2- vinyldithiine. Cette dernière dérive de l’allicine, la molécule produite par la réaction enzymatique entre l’alliine et l’alliinase. Une étude de l’alliine et de ses mécanismes réactionnels constitue dès lors un sujet de recherche pertinent. Dans un premier temps, le but du travail consistait en l’obtention d’une réserve d’alliine afin d’étudier sa réaction. Cependant, la synthèse de l’alliine mène à un mélange de diastéréoisomères (57 % de (-)alliine contre 43 % de (+)), alors que seule la forme (+) existe naturellement. L’obtention de cette molécule à une pureté relativement importante est devenu notre objectif. Ensuite, certains paramètres de la réaction enzymatique ont été mesurés. Un premier développement intéressant fut la mise au point d’une méthode HPLC de séparation des diastéréoisomères sur une colonne de graphite de carbone poreux. Diverses voies ont ensuite été expérimentées pour améliorer la proportion finale en (+)alliine dans notre échantillon. La purification à partir de gousses d’ail s’est révélée longue, bien que la chromatographie sur silice conduise à des résultats intéressants (Pureté HPLC de 90 %). Une synthèse enzymatique améliore l’excès énantiomèrique mais uniquement de quelques pourcents (diastereoisomeric excess, de = 26 %). Une séparation est observée par le procédé de Stein et Moore (chromatographie échangeuse d’ions pour acides aminés). Les meilleurs résultats ont été mis en évidence sur une colonne aminopropyle. Dans ce cas, la proportion en (+)alliine atteint les 95 %. Enfin, l’activité enzymatique spécifique mesurée vaut 45,8 μmoles de pyruvate par minute et par gramme de protéine. La méthode HPLC développée semble plus performante que celles qui sont décrites dans la littérature. La résolution a été améliorée, permettant une bonne distinction des diastéréoisomères. Parmi les techniques de production de (+)alliine testées à partir de la synthèse, la chromatographie échangeuse d’ions analytique donnait des résultats encourageants. Cette voie pourrait être expérimentée plus longuement. Une méthode HPLC sur phase aminopropyle donnait également lieu à une bonne séparation, et le passage sur colonne classique fut un succès (de > 90 %). La purification de gousses donne un résultat équivalent, mais le procédé est long et le rendement plus faible. Pour clôturer, l’activité enzymatique spécifique mesurée correspond aux valeurs citées dans la littérature. [less ▲]

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