Ruminal biohydrogenation of alpha-linolenic acid is not fully understood compared with that of linoleic acid. Some hypothetical intermediates, that is, conjugated isomers of alpha-linolenic acid (cis-9,trans-11,cis-15 and cis-9,trans-13,cis-15 18:3) have never been reported to occur in ruminant fat. Therefore, milk fat was analyzed using a combination of techniques to characterize alpha-linolenic acid biohydrogenation intermediates. Tandem off-line argentation thin-layer chromatography and high-resolution gas-liquid chromatography using a 120-m highly polar, open tubular capillary column coated with 70% cyanoalkyl polysiloxane equivalent material was used for quantification. Structural characterization of fatty acids was achieved by gas-chromatography mass-spectrometry after synthesis of specific azo-derivatives. This study confirmed that minute amounts of alpha-linolenic acid biohydrogenation intermediates are present in milk fat. Routes involved in biohydrogenation of linoleic and alpha-linolenic acids in the rumen and subsequent endogenous metabolism of related biohydrogenation products are discussed.

Chitosan treatment (2-8 mg/mL) of wheat seeds significantly improved seed germination to recommended seed certification standards (>85%) and vigor at concentrations >4 mg/mL, in two cultivars of spring wheat (Norseman and Max), by controlling seed-borne Fusarium graminearum infection. The germination was <80% in the control and >85% in benomyl- and chitosan-treated seeds. Seed-borne F. graminearum was reduced to >50% at higher chitosan treatments compared to the control. Synthesis of phenolic acids was stimulated in primary leaves following chitosan treatment, and levels of these phenolic acids, especially ferulic acid, increased significantly with increasing chitosan concentration. Lignin content of primary leaves also showed a similar pattern. The synthesis of precursors of lignin such as p-coumaric, ferulic, and sinapic acids and phenolic acids having antimicrobial activity such as benzoic, p-coumaric, caffeic, protocatechuic, chlorogenic, ferulic, and gallic acids was also stimulated by chitosan treatment. The induction of phenolic acids and lignin was significantly lower in cv. Max compared to Norseman. Chitosan also inhibited fungal transmission to the primary roots of germinating seedlings. Results suggest that chitosan controlled seed-borne F. graminearum infection and increased the resistance in seedlings by stimulating the accumulation of phenolics and lignin. Thus, chitosan has a potential for improvement of seed quality and enhancement of crop yields as well as increased value of stored grains for food and feed.

Picolinyl derivatives are used for structural determination of FA by GC-MS. Although they provide reliable diagnostic fragments, the usual multistep methodologies applied for their preparation require TAG hydrolysis or acid chloride formation prior to picolinyl synthesis. These reaction conditions may result in the presence of artifact molecules in the samples and thus compromise analytical quality and accuracy. To address these problems, a rapid, simple and quantitative methodology for the synthesis of FA picolinyl esters from intact lipids was developed. It involves their transesterification under basecatalyzed conditions using 3-potassiooxamethylpyridine in methylene chloride. The catalyst was prepared by proton exchange between potassium tert-butoxide and anhydrous 3-hydroxymethylpyridine. Mild reaction conditions allowed complete derivatization of TAG and phospholipids in 2 min at room temperature, and of FAME in 15 min at 45°C. The proposed procedure, which can be used on a routine basis, was applied to Ipomoae imperialis seed lipids and used to confirm occurrence of γ-linoleic acid at a level of 0.9%.Paper no. J10108 in JAOCS 79, 253-256 (March 2002). KEY WORDS:Alkoxide, fatty acid picolinyl ester, gas-liquid chromatography, Ipomoae seed oil, γ-linolenic acid, mass spectrometry, mass spectroscopy, potassium tert-butoxide, transesterification.Derivatization is a necessary step prior to structural determination of FA by GC-MS. However, mass spectra of FAME, the usual derivatives for GLC-FID analysis, are devoid of sufficient information for identification of structural isomers. This is mainly due to the high sensitivity of the carboxyl group to fragmentation and to double bond migration (1,2). However, stabilization of the carboxyl group by the formation of a derivative containing a nitrogen atom results in mass spectra that allow structural determination for most FA (1). A first such derivative used in GC-MS analysis was pyrrolidide (3), but structural determination of FA by this technique is now usually performed using picolinyl and 4,4-dimethyloxazoline derivatives. Indeed, these FA derivatives provide diagnostic fragments that allow accurate structure determination (1). However, the usual multistep methodologies for the synthesis of picolinyl esters require hydrolysis of the lipid sample prior to final derivatization, either by condensation of the formed acid chloride with 3-hydroxymethylpyridine (1) or through an imidazole intermediate (4). The latter methodology was developed for the analysis of sensitive FA containing polyethylenic bond systems or an epoxy group. Both procedures give accurate qualitative and quantitative results but require long reaction times, which do not always lead to complete derivatization, and moderate to high temperatures that may result in artifacts. The aim of this study was to develop a short, simple, and quantitative procedure for the synthesis of FA picolinyl esters in mild conditions and from O-acetylated acids. The proposed methodology was applied to confirm occurrence ...

Abstract:Developed from crosses between Vitis vinifera and North American Vitis species, interspecific hybrid grape varieties are becoming economically significant in northern areas, where they are now extensively grown for wine production. However, the varietal differences between interspecific hybrids are not well defined, nor are the relationships between hybrid grape and wine composition, which causes significant drawbacks in the development of viticulture and winemaking of northern wines. In an effort to increase our understanding of interspecific hybrids, we have characterized the free volatile compounds profiles of berries (juice and skin) and wines of five red hybrid varieties (Frontenac, Marquette, Maréchal Foch, Sabrevois and St. Croix) grown in Québec (Canada), using GC-MS(TOF)-SPME. In grapes and wines, significantly higher levels of C6 and other fatty acid degradation products (FADP) were found in Frontenac, Maréchal Foch and Marquette. Terpenes were primarily located in the skin, with Marquette showing the highest level for these compounds. Both the level of terpenes and the level of FADP in grape were strongly correlated with their respective levels in wine, as demonstrated by the redundancy analyses. Nonanal, (E,Z)-2,6-nonadienal, β-damascenone, ethyl octanoate and isoamyl acetate showed the highest OAVs in the wines of the studied varieties.

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Linoleic acid was heated at 200 degrees C under helium. Analysis of degradation products by GC on a long polar open tubular capillary column showed the presence of CLA isomers. The identified mono trans CLA isomers were cis-9,trans-11, trans-9,cis-11, trans-10,cis-12, cis-10,trans-1 2, trans-8,cis-10, and cis-11,trans-13 18:2 acids. Oils containing different levels of linoleic acid (peanut, sesame seed, and safflower seed oils) were also heat treated, resulting in similar CLA distributions. Elution order was confirmed using cis-9,trans-11 and trans-10,cis-1 2 acid methyl esters standards and their respective configuration isomers (trans-9,cis-11, cis-10,trans-12), obtained after mild selenium-catalyzed isomerization. These results indicated that two conjugated mono trans isomers of 18:2 acid, cis-8,trans-10 and trans-11,cis-13 18:2 were absent from the series, thus strongly suggesting that some constraints were preventing their formation. By heating pure methyl rumenate (cis-9,trans-11 18:2) under similar conditions, isomerization resulted principally in a nearly equimolar mixture of methyl rumenate and trans-8,cis-10 18:2. Similarly, the methyl ester of trans-10,cis-12 18:2 acid was partially transformed into cis-11 ,trans-13 18:2 acid. Respective geometrical isomers were also formed in trace amounts. A concerted pericyclic isomerization mechanism, a [1,5] sigmatropic rearrangement, is proposed that limits the conjugated system to isomerization from a cis-trans acid to a trans-cis acid, and vice versa. This mechanism is consistent with undetected cis-8,trans-10 and trans-11,cis-13 18:2 isomers in heated oils containing linoleic acid.