Antioxidant mechanism of grape procyanidins in muscle tissues: redox interactions with endogenous ascorbic acid and α-tocopherol.

The present study investigates the antioxidant mechanism of grape procyanidins and, in particular, their aptitude to establish redox interactions with two important components of the endogenous antioxidant system of muscle tissues, α-tocopherol (α-TOH) and ascorbic acid (AA). To this end, the progress of lipid oxidation was monitored in fish muscle supplemented with grape procyanidins at the concentrations usually employed in antioxidant food applications, and then related to the redox stability of the endogenous α-TOH and AA. In addition to the lipid oxidation protective effect, the incorporation of procyanidins also provided an improvement of the redox stability of the endogenous components in a straight procyanidinic concentration-dependent manner.

Isotopic labeling of metabolites in drug discovery applications.

Understanding the metabolic and pharmacokinetic fate of a drug in humans is a key factor in its development and registration, as well as in the elaboration of new therapeutic agents. To carry out these studies, stable isotope labeling techniques have been effectively used by drug metabolism scientists and toxicologists in order to gain better understanding of the drugs' disposition, bioavailability and toxicity in in vivo studies. Among the different analytical techniques used, mass spectrometry (MS) coupled to separation techniques has become the detection method of choice due to its high sensitivity and selectivity.

Dissociation of deprotonated microcystin variants by collision-induced dissociation following electrospray ionization.

Microcystins (MC) are a family of hepatotoxic cyclic heptapeptides produced by a number of different cyanobacterial species. Considering the recent advances in the characterization of deprotonated peptides by mass spectrometry, the fragmentation behavior of four structurally related microcystin compounds was investigated using collision-induced dissociation (CID) experiments on an orbitrap mass spectrometer. It is demonstrated in this study that significant structural information can be obtained from the CID spectra of deprotonated microcystins.

Structure-activity relationships of polyphenols to prevent lipid oxidation in pelagic fish muscle.

The influence of polymerization (number of monomers) and galloylation (content of esterified gallates) of oligomeric catechins (proanthocyanidins) on their effectiveness to prevent lipid oxidation in pelagic fish muscle was evaluated. Non-galloylated oligomers of catechin with diverse mean polymerization (1.9-3.

Contribution of galloylation and polymerization to the antioxidant activity of polyphenols in fish lipid systems.

Polyphenolic fractions extracted from pine (Pinus pinaster) bark, grape (Vitis vinifera) pomace, and witch hazel (Hamamelis virginiana) bark were selected for investigating the influence of the number of phenolic units, polymerization, and the content of esterified galloyl residues (galloylation) on their efficacy for inhibiting lipid oxidation in fish lipid enriched foodstuffs. Experiments carried out with nongalloylated pine bark fractions with different polymerization degrees demonstrated that the number of catechin residues per molecule modulates their reducing and chelating properties in solution. In real food systems such as bulk fish oil and fish oil-in-water emulsions, the efficacy against lipid oxidation was highly dependent on the physical location of the antioxidant at the oxidative sensitive sites.

Capacity of reductants and chelators to prevent lipid oxidation catalyzed by fish hemoglobin.

The efficiency of different reductants (reduced glutathione, ascorbic acid, and catalase) and metal chelators [ethylenediaminetetraacetic acid (EDTA), citric acid, sodium tripolyphosphate (STPP), and adenosine-5'-triphosphate (ATP)] to inhibit lipid oxidation promoted by fish hemoglobin was investigated. The inhibitory activity on hemoglobin-catalyzed lipid oxidation was also evaluated for grape oligomeric catechins (proanthocyanidins), which have both reducing and chelating properties. The antioxidant activity was studied in two different lipid oxidation models, liposomes and washed minced fish muscle.

Caffeic acid as antioxidant in fish muscle: mechanism of synergism with endogenous ascorbic acid and alpha-tocopherol.

In an emulsion of corn oil in water with the addition of caffeic acid (Caf-OH) and alpha-tocopherol (alpha-TOH), Caf-OH was found to be very active in delaying lipid oxidation without affecting significantly the kinetics for alpha-TOH degradation. In contrast, Caf-OH addition to fish muscle retarded both the degradation of endogenous alpha-TOH and the propagation of lipid oxidation, measured by peroxide value (PV) and thiobarbituric acid reactive substances (TBARS), with increasing effect with increasing Caf-OH addition (55.5-555.

Solid-phase microextraction method for the determination of volatile compounds associated to oxidation of fish muscle.

A procedure for the determination of volatile compounds derived from lipid oxidation of fish muscle samples is presented. Analytes are concentrated on a solid-phase microextraction fiber employed in the headspace mode (HS-SPME), and selectively determined using gas chromatography in combination with mass spectrometry (GC-MS). The influence of several parameters on the efficiency of microextraction such as type of fiber, volume of sample, time, temperature, salting-out effect and stirring was systematically investigated.

Development of a solid-phase microextraction method for determination of volatile oxidation compounds in fish oil emulsions.

Headspace solid-phase microextraction (HS-SPME) is proposed for isolating and determining the headspace volatiles formed during oxidation of fish-oil-in-water emulsions. Three different fiber coatings were tested and compared for sensitivity and reproducibility. A carboxen/polydimethylsiloxane (CAR-PDMS) fiber coating was found to be the most suitable for the analysis of emulsion volatiles.