Identification of cholesteryl ester of ferulic acid in human plasma by mass spectrometry.

Epidemiological data suggests that regular consumption polyphenol rich foods and beverages is associated with a reduced risk of certain pathological conditions. While the in vivo "per se" antioxidant benefit of polyphenols still has not been clearly demonstrated, it has been suggested that phenolic acids can be incorporated into low-density lipoproteins (LDL). In the present study, we hypothesized that esterification of phenolic acids - such as ferulic acid - with lipophilic substances such as cholesterol can occur in vivo. To prove this hypothesis, we have synthesized pure cholesteryl-ferulate standard and used gas- and liquid chromatography coupled with mass spectrometry to confirm the presence of endogenous form in human plasma. The detection and identification of cholesteryl ferulate was based on: (1) matching gas- and liquid chromatographic retention time with the reference standard; (2) accurate mass of the molecular ion; (3) matching electron ionization mass spectrum and (4) matching electrospray product ion spectrum. The identified cholesteryl ferulate demonstrated an in vitro antioxidant capacity in various assays. The present study confirmed that phenolic acid can be found in human plasma as lipophilic conjugates which exert antioxidant capacity. These molecules can potentially be involved in the protection of lipoproteins against oxidative damages.

First synthesis, characterization, and evidence for the presence of hydroxycinnamic acid sulfate and glucuronide conjugates in human biological fluids as a result of coffee consumption.

A systematic investigation of the human metabolism of hydroxycinnamic acid conjugates was carried out. A set of 24 potential human metabolites of coffee polyphenols has been chemically prepared, and used as analytical standards for unequivocal identifications. These included glucuronide conjugates and sulfate esters of caffeic, ferulic, isoferulic, m-coumaric and p-coumaric acids as well as their dihydro derivatives. A particular focus has been made on caffeic and 3,4-dihydroxyphenylpropionic acid derivatives, especially the sulfate conjugates, for which regioselective preparation was particularly challenging, and have so far never been identified as human metabolites. Ten out of the 24 synthesized conjugates have been identified in human plasma and/or urine after coffee consumption. A number of these conjugates were synthesized, characterized and detected as hydroxycinnamic acid metabolites for the first time. This was the case of dihydroisoferulic acid 3'-O-glucuronide, caffeic acid 3'-sulfate, as well as the sulfate and glucuronide derivatives of 3,4-dihydroxyphenylpropionic acid.

Comparison of mass spectrometry-based electronic nose and solid phase microextraction gas chromatography-mass spectrometry technique to assess infant formula oxidation.

Two headspace techniques based on mass spectrometry detection (MS), electronic nose, and solid phase microextraction coupled to gas chromatography-mass spectrometry (SPME-GC/MS) were evaluated for their ability to differentiate various infant formula powders based on changes of their volatiles upon storage. The electronic nose gave unresolved MS fingerprints of the samples gas phases that were further submitted to principal component analysis (PCA). Such direct MS recording combined to multivariate treatment enabled a rapid differentiation of the infant formulas over a 4 week storage test. Although MS-based electronic nose advantages are its easy-to-use aspect and its meaningful data interpretation obtained with a high throughput (100 samples per 24 h), its greatest disadvantage is that the present compounds could not be identified and quantified. For these reasons, a SPME-GC/MS measurement was also investigated. This technique allowed the identification of saturated aldehydes as the main volatiles present in the headspace of infant milk powders. An isotope dilution assay was further developed to quantitate hexanal as a potential indicator of infant milk powder oxidation. Thus, hexanal content was found to vary from roughly 500 and 3500 microg/kg for relatively non-oxidized and oxidized infant formulas, respectively.