La methode de separation electrocinetique donnee peut etre consideree comme un type de chromatographie de partage liquide-liquide ne necessitant pas de support solide pour maintien de la phase liquide stationnaire, et dans laquelle les micelles sont considerees comme une pseudo-phase

Electrokinetic separations with micellar solutions and open-tubular capillaries

A series of 25 virgin and refined edible oils, obtained from retailers, was analyzed for levels of free 3-chloropropane-1,2-diol (3-MCPD) and 3-MCPD released from esters with higher fatty acids (bound 3-MCPD). Oils containing free 3-MCPD ranging from <3 microg kg-1 (LOD) to 24 microg kg-1. Surprisingly, bound 3-MCPD levels were much higher and varied between <100 (LOD) and 2462 microg kg-1. On average, virgin oils had relatively low levels of bound 3-MCPD, ranging from <100 (LOD) to <300 microg kg-1 (LOQ). Higher levels of bound 3-MCPD were found in oils from roasted oilseeds (337 microg kg-1) and in the majority of refined oils (<300-2462 microg kg-1), including refined olive oils. In general, it appears that the formation of bound 3-MCPD in oils is linked to preliminary heat treatment of oilseeds and to the process of oil refining. Analysis of unrefined, de-gummed, bleached, and deodorized rapeseed oil showed that the level of bound MCPD decreased during the refining process. However, additional heating of seed oils for 30 min at temperatures ranging from 100 to 280 degrees C, and heating at 230 degrees C (260 degrees C) for up to 8 h, led to an increase in bound 3-MCPD levels. On the other hand, heating of olive oil resulted in a decrease in bound 3-MCPD levels. For comparison, fat isolated from salami was analyzed for intact fatty acid esters of 3-MCPD. This fat contained bound 3-MCPD at a level of 1670 microg kg-1 and the fatty acid esters of 3-MCPD mainly consisted of 3-MCPD diesters; monoesters of 3-MCPD were present in smaller amounts. The major types of 3-MCPD diesters (about 85%) were mixed diesters of palmitic acid with C18 fatty acids (stearic, oleic, linoleic acids). These diesters were followed by 3-MCPD distearate (11%) and 3-MCPD dipalmitate (4%). Generally, very little 3-MCPD existed as the free compound (31 microg kg-1).

Fatty acid esters of 3-chloropropane-1,2-diol in edible oils.

Most reports on the identification of known flavonoids in new plant sources as well as those on novel flavonoids naturally deal with the two most abundant classes, the flavones and flavonols. For this chapter we have listed all references to the occurrence of flavone and flavonol aglycones which have appeared from 1975 to 1980, and also include such earlier references as were overlooked in the relevant chapters of The Flavonoids’ (1975). Emphasis is given to the natural distribution of these compounds. The data are collected in Tables 4.1 and 4.2 which cite substances, plant sources and references. Since 1974, some 50 flavones and 60 flavonols with common substitution patterns have been described as novel compounds. Many are simply new methyl ethers of known compounds. The structures are arranged throughout the Tables by number and arrangement of substituents in ring A, followed by ring B. Wherever possible, the plant organs from which the compounds have been isolated are cited. In cases where authors have extracted the ‘whole plant’ or ‘aerial parts’, it does not necessarily follow that the compound is present in all parts, since these substances are often specifically located in certain organs only. In all cases where free aglycones are encountered, especially highly methylated flavonoids, it is likely that they occur externally, or are associated with secretory structures and are correlated with the production of other lipophilic secondary compounds, mainly of terpenoid origin.

Flavones and Flavonols

3-Mono-chloropropane-1,2-diol (3-MCPD) is a contaminant that occurs in food in its free (diol) form as well as in an esterified (with fatty acids) form. Using a simple intestinal model, it was demonstrated that 3-MCPD monoesters and 3-MCPD diesters are accepted by intestinal lipase as substrates in vitro. Under the chosen conditions, the yield of 3-MCPD from a 3-MCPD monoester was greater than 95% in approximately 1 min. Release from the diesters was slower, reaching about 45, 65 and 95% of 3-MCPD after 1, 5 and 90 min of incubation, respectively. However, in human, the hydrolysis of 3-MCPD esters is unlikely to release 100% as 3-MCPD, as triglycerides and phospholipids are hydrolysed in the intestine liberating 2-monoglycerides. Assuming a similar metabolism for 3-MCPD esters as that known for acylglycerols in humans in vivo, the de-esterification in positions 1 and 3 would thus be favoured by pancreatic lipases. Therefore, 3-MCPD, and 3-MCPD-2 monoesters would be released, respectively, from the 1-/3-monoesters, and the diesters potentially present in food. Hence, information on the exact amounts of the partial fatty acid chloroesters, i.e. 3-MCPD mono- and diesters, is important to assess the contribution of foods to the bioavailability of 3-MCPD. Therefore, a rapid method for the determination of the ratio of 3-MCPD monoesters to diesters in fats and oils was developed using gas chromatography-mass spectrometry (GC-MS) and isotopically labelled 3-MCPD esters as internal standards. The analysis of 11 different samples of fat mixes typically employed in food manufacturing demonstrated that a maximum of about 15% of the total amount of 3-MCPD bound in esters is present in the monoesterified form. The potentially slower release of 3-MCPD from 3-MCPD diesters, and the mono- to diesters ratio suggest that 3-MCPD esters may in fact contribute only marginally to the overall dietary exposure to 3-MCPD. Further work on the bioavailability, metabolism and possible toxicity of chloroesters per se is warranted.

Esters of 3-chloro-1,2-propanediol (3-MCPD) in vegetable oils: Significance in the formation of 3-MCPD

Publisher Summary This chapter presents a review about the chemistry and developments of fluorinated carbohydrates. Because of the high C–F bond energy, glycosyl fluorides are stable in comparison to the other glycosyl halides, and this character has attracted much attention. Deoxyfluoro sugars labeled with fluorine-18 have important applications as imaging agents. Numerous 5-fluorouracil derivatives have been prepared as potential anticancer agents. Fluorine-18 is not known naturally (natural fluorine is all 19 F), but it may be prepared in a variety of artificial nuclear reactions. Several 1-phosphates of deoxyfluoro sugars have been prepared and their acid-catalyzed hydrolysis has been studied. The fluorination of aminoglycosides and anticancer antibiotics has been undertaken to obtain the derivatives of enhanced activity and decreased toxicity. The knowledge concerning the conformation of nucleosides is important in pursuing the relationship between the structure and biological activity of compounds containing fluorinated carbohydrates. Much effort has been devoted to preparing natural nucleoside analogs having effective antiviral (mostly antiherpetic) and antitumor activities with low cytotoxicity for the host cells.

Chemistry and Developments of Fluorinated Carbohydrates

Nucleoside von fluorzuckern- VI

Halogenolipids. I. Mass Spectrometric Structure Investigation of the Isomeric Halogeno-propanediols Esterified with Fatty Acids (Deoxyhalogeno-glycerides)



The mass spectrometric behaviour of the isomers of cytostatic effective halogeno-propanediols esterfied with fatty acids (deoxyhalogeno-monoglycerides and deoxyhalogeno-diglycerides) are investigated. The unambiguous structure of individual isomers is deduced from the characteristic fragmentation patterns of mass spectra. The synthesis of the mentioned compounds is described.

Halogenlipide. I. Massenspektrometrische Strukturuntersuchung stellungsisomerer Fettsäureester der Halogenpropandiole (Desoxyhalogen‐glyceride)

Die Kondensation von 2-Desoxy-3.4.6-tri-O-acetyl-D-glucopyranosylbromid (I) mit Monoquecksilberverbindungen des Thymins, 5-Fluor-, 5-Brom-, 5-Joduracils und Uracils (IIa–e) in Dimethylformamid liefert nach basen- oder protonenkatalysierter Entacylierung die entsprechenden 1-[2-Desoxy-α.β-D-glucopyranosyl]-pyrimidin-Derivate (α.β-IVa–e). Die α- bzw. β-Anomeren wurden entweder isoliert oder angereichert. Die Untersuchung der Hemmwirkung dieser Nucleoside und ihrer Pyrimidin-Basen auf die Spaltung von Desoxyuridin durch Extrakte aus Ascites-Tumorzellen ergab, das in allen Fallen die β-Anomeren wirksamer sind als die α-Anomeren und die freien Basen.

Pyrimidin-nucleoside der 2-Desoxy-D-glucose

Combined thin-layer chromatography/mass spectrometry without substance elution. Use of direct identification of phenols, steroids, nucleosides, biogenic amines, and amino acids.

Die massenspektrometrischen Zerfallsprodukte der vier isomeren phenyl-substituierten Amino-oxadiazole, 2-Amino-5-phenyl-l.3.4-oxadiazol, 3-Amino-5-phenyl-l.2.4-oxadiazol, 5-Amino-3-phenyl-l.2.4-oxadiazol und 3-Amino-4-phenyl-l.2.5.oxadiazol, unterscheiden sich sowohl hinsichtlich der Art der Fragmentzusamrnensetzung als auch der Signalintensitaten so charakteristisch, das eine eindeutige Differenzierung von Ring- und Stellungsisomeren moglich ist. Die wichtgsten Fragmentierungswege, die zu den strukturspezifischen Ionen fuhren, werden diskutiert.



The mass spectrometric fragmentation products of the four isomeric monophenyl amino oxadiazoles, 2-amino-5-phenyl-l, 3,4-oxadiazole, 3-amino-5-phenyl-l, 2, 4-oxadiazole, 5-amino-3 phenyl-l, 2, 4-oxadiazole and 3-amino-4-phenyl-1, 2,5-oxadiazole, differ with respect to their fragment composition and abundance in such a way that isomers can easily be distinguished and determined. The most important fragmentation patterns giving characteristic ions for structure identification are discussed.

G. Etzold

Papers

Nucleoside von fluorzuckern- VI

Halogenlipide. I. Massenspektrometrische Strukturuntersuchung stellungsisomerer Fettsäureester der Halogenpropandiole (Desoxyhalogen‐glyceride)

Pyrimidin-nucleoside der 2-Desoxy-D-glucose

Combined thin-layer chromatography/mass spectrometry without substance elution. Use of direct identification of phenols, steroids, nucleosides, biogenic amines, and amino acids.

Anwendung der Massenspektrometrie zur Identifizierung isomerer Amino‐oxadiazole