Analysis of the diastereoisomers of alliin by HPLC.

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 cysteine sulfoxide, and to analyze an 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.

Validation of a fast gas chromatographic method for the study of semiochemical slow release formulations.

The validation of a fast GC-FID analytical method for the quantitative determination of semiochemical sesquiterpenes (E-beta-farnesene and beta-caryophyllene) to be used in an integrated pest management approach is described. Accuracy profiles using total error as decision criteria for validation were used to verify the overall accuracy of the method results within a well defined range of concentrations and to determine the lowest limit of quantification for each analyte. Furthermore it allowed to select a very simple and reliable regression model for calibration curve for the quantification of both analytes as well as to provide measurement uncertainty without any additional experiments. Finally, this validated method was used for the quantification of semiochemicals in slow release formulations. The goal was to verify the protection efficiency of alginate gel beads formulations against oxidation and degradation of sesquiterpenes. The results showed that the alginate beads are adequate slow release devices which protect the bio-active molecules during at least twenty days.

Enzymatic interesterification of anhydrous milk fat with rapeseed and/or linseed oil: oxidative stability.

Blends of anhydrous milk fat (AMF) and linseed oil (70:30) and of AMF, rapeseed oil (RO), and linseed oil (LO) (70:20:10) were submitted to enzymatic interesterification. The oxidative stabilities of the blends, the interesterified (IE) blends, and IE blends with 50 ppm of alpha-tocopherol added as antioxidant were studied. Samples were stored in open flasks at 60, 25, and 4 degrees C and periodically submitted to peroxide, p-anisidine, and TBA value determinations and UV measurement at 232 and 268 nm. The analysis of volatile compounds was carried out by SPME for the samples stored at 60 degrees C. Peroxides appeared to be the only significant oxidation products after 12 weeks of storage at 4 degrees C. As expected, the binary blends (BB) were more sensitive to oxidation than the ternary blends (TB). The BB were associated with increased volatile emission compared to the TB. Interesterification led to variable effects on the oxidation of fat mixtures, depending on composition and temperature (beneficial effect on BB, at both 25 and 60 degrees C, and a rather neutral effect on TB). The IE blends exhibited higher volatile release prior to aging. A pro-oxidant effect of alpha-tocopherol addition was observed at 25 degrees C on both BB and TB. At 60 degrees C, an antioxidant effect was observed on TB.

Fast gas chromatography characterisation of purified semiochemicals from essential oils of Matricaria chamomilla L. (Asteraceae) and Nepeta cataria L. (Lamiaceae).

The chemical composition of Matricaria chamomilla L. and Nepeta cataria L. essential oils was determined by GC-MS on an apolar stationary phase by comparison of the characteristic fragmentation patterns with those of the Wiley 275L database. The GC-MS chromatograms were compared with those obtained by fast GC equipped with a direct resistively heated column (Ultra Fast Module 5% phenyl, 5 mx 0.1 mm, 0.1 microm film thickness). Analytical conditions were optimised to reach a good peak resolution (split ratio=1:100), with analysis time lower than 5 min versus 35-45 min required by conventional GC-MS. The fast chromatographic method was completely validated for the analysis of mono- and sesquiterpene compounds. Essential oils were then fractionated by column chromatography packed with silica gel. Three main fractions with high degree of purity in E-beta-farnesene were isolated from the oil of M. chamomilla. One fraction enriched in (Z,E)-nepetalactone and one enriched in beta-caryophyllene were obtained from the oil of N. cataria. These semiochemical compounds could act as attractants of aphid's predators and parasitoids.