Analytical strategies to assess the functional metabolome of vitamin E.

After more than 90 years from its discovery and thousands of papers published, the physiological roles of vitamin E (tocopherols and tocotrienols) are still not fully clarified. In the last few decades, the enzymatic metabolism of this vitamin has represented a stimulating subject of research. Its elucidation has opened up new horizons to the interpretation of the biological function of that class of molecules. The identification of specific properties for some of the physiological metabolites and the definition of advanced analytical techniques to assess the human metabolome of this vitamin in vivo, have paved the way to a series of hypotheses on the functional implications that this metabolism may have far beyond its catabolic role. The present review collects the available information on the most relevant analytical strategies employed to assess the status and metabolism of vitamin E in humans as well as in other model systems. A particular focus is dedicated to the analytical methods used to measure vitamin E metabolites, and particularly long-chain metabolites, in biological fluids and tissues. Preliminary information on a new LC-APCI-MS/MS method to measure these metabolites in human serum is reported.

A comprehensive study for the validation of a LC-MS/MS method for the determination of free and total forms of urinary cortisol and its metabolites.

Several pathological conditions can be related to the alteration of the urinary levels of cortisol (F) and its metabolites. The determination of each of them in the free and free plus conjugated form can provide a deeper insight into the impaired activity of the cortisol metabolism enzymes, thus improving the diagnosis protocol currently based only on the determination of total amount of urinary cortisol metabolites. In that view, an LC-MS/MS method for the determination of the free and total amount of urinary F, cortisone (E), tetrahydrocortisol (THF), allo-tetrahydrocortisol (A-THF) and tetrahydrocortisone (THE) was thus developed and validated. Deconjugation of glucocorticoids was carried out by enzymatic hydrolysis. Analytes were extracted by solid phase extraction, separated by liquid chromatography and analyzed via electro-spray ionization (negative ion mode) triple-quadrupole mass spectrometry in the selected reaction monitoring mode using a stable isotope-labeled internal standard. Baseline separation for all compounds, in particular the two stereoisomers A-THF and THF, was obtained. Matrix effects, not reported so far, were observed and minimized for the determination of urinary free E and THE. Validated range was 0.5-1000ng/mL for A-THF and THF, 5-800ng/mL for E and THE and 1-1000ng/mL for F, with R(2) values greater than 0.9981. The LOD and LOQ of the described method ranged from 0.1 to 3.0ng/mL, while the extraction recoveries resulted close to 100% for all the glucocorticoids determined. Precision and accuracy were well within ±10%. As suggested by the results obtained in the preliminary study on polycystic ovary syndrome (PCOS) urine samples, the method can be used to support clinical diagnosis of pathologies related to cortisol metabolism. In fact, levels of free and total glucocorticoids in control subjects were in agreement with previously reported data, as well as free and total A-THF/THF ratio in PCOS patients. Conversely, in the latter free F/E and A-THF+THF/THE ratios were lower than in control subjects (P<0.01), suggesting a possible alteration of 11ß-HSD1 and 11ß-HSD2 activity, to be further investigated.

Wolf howling is mediated by relationship quality rather than underlying emotional stress.

While considerable research has addressed the function of animal vocalizations, the proximate mechanisms driving call production remain surprisingly unclear. Vocalizations may be driven by emotions and the physiological state evoked by changes in the social-ecological environment, or animals may have more control over their vocalizations, using them in flexible ways mediated by the animal's understanding of its surrounding social world. While both explanations are plausible and neither excludes the other, to date no study has attempted to experimentally investigate the influence of both emotional and cognitive factors on animal vocal usage. We aimed to disentangle the relative contribution of both mechanisms by examining howling in captive wolves. Using a separation experiment and by measuring cortisol levels, we specifically investigated whether howling is a physiological stress response to group fragmentation and whether it is driven by social factors, particularly relationship quality. Results showed that relationship quality between the howler and the leaving individual better predicted howling than did the current physiological state. Our findings shed important light on the degree to which animal vocal production can be considered as voluntary.

Tocopheramines and tocotrienamines as antioxidants: ESR spectroscopy, rapid kinetics and DFT calculations.

Tocopheramines (TNH2) and tocotrienamines (T3NH2) are analogues of tocopherols (TOH) and tocotrienols in which phenolic OH is replaced by NH2. It was shown in previous studies that TNH2 and T3NH2 act as potent antioxidants. In this study we compared the one-electron oxidation of TNH2/T3NH2 by diphenyl picryl hydrazyl (DPPH) and galvinoxyl (GOX) radicals with the one of α-TOH as a reference compound using ESR spectroscopy, stopped flow spectrophotometry and density functional theory (DFT) calculations. ESR spectroscopy revealed the presence of tocopheramine radicals during electrochemical oxidation of α-TNH2. Kinetic measurements demonstrated that in apolar n-hexane TNH2/T3NH2 derivatives reacted two to three orders of magnitude slower than α-TOH with the model radicals. DFT calculations indicated that this correlates well with the higher bond dissociation energy (BDE) for N-H in TNH2 than for O-H in α-TOH in pure H-atom transfer (HAT). In the more polar medium ethanol TNH2/T3NH2 derivatives partially reacted faster than α-TOH depending on the reaction partner. DFT calculations suggest that this is due to reaction mechanisms alternative to HAT. According to thermochemistry data sequential proton loss and electron transfer (SPLET) is more favored for α-TOH in ethanol than for TNH2. Therefore, for TNH2 a contribution of the alternative mechanism of sequential electron transfer-proton transfer (SET-PT) could be a possible explanation. These data show that the antioxidant reactivity strongly depends on the structure, reaction partners and environment. According to these findings TNH2/T3NH2 should be superior as antioxidants over α-TOH in polar head group regions of membranes but not in the apolar core of lipid bilayers.

Mitochondrial-dependent anticancer activity of δ-tocotrienol and its synthetic derivatives in HER-2/neu overexpressing breast adenocarcinoma cells.

Anticancer activity and mitochondrial mechanism of the vitamin E form δ-tocotrienol (δ-T3) was investigated in HER-2/neu-overexpressing human SKBR3 and murine TUBO breast cancer cells. δ-T3 was confirmed to possess high cytotoxic and apoptotic activity in SKBR3 cells as compared with all natural forms of vitamin E and several synthetic forms that included novel derivatives with the same backbone of δ-T3 such as δ-tocotrienyl-succinyl amide (δ-T3AS) and the redox-active analogue δ-tocotrienyl amine (δ-T3NH2). As observed in the case of alpha-TOS, a prototypical anticancer drug derived from α-tocopherol, succinylation of δ-T3 enhanced citotoxicity and apoptotic activity of the vitamer. δ-T3 induced apoptosis of SKBR3 cells was associated with mitochondrial destabilization, energy failure, and unbalanced activity of stress/survival MAPKs, namely p38 and ERK1/2 pathways. An increased generation of ROS followed to such a series of early events. Enhanced activity of δ-T3 in this human carcinoma cell line was characterized by the sustained uptake and oxidative transformation to the quinone derivative δ-T3Q, thereby suggesting redox effects in SKBR3 mitochondria by this vitamer. Viability and uptake data show a different pattern of responses in TUBO cells with higher response to synthetic derivatives of δ-T3 than in SKBR3 cells. In conclusion, synthetic derivatives of δ-T3 with enhanced apoptotic activity in breast carcinoma cells are investigated for the first time in this study also describing mechanistic aspects of mitochondrial effects of δ-T3. Further investigation in preclinical models of HER2/neu-high breast adenocarcinoma is underway to identify other and more effective forms of VE in this type of cancer.

Why tocotrienols work better: insights into the in vitro anti-cancer mechanism of vitamin E.

The selective constraint of liver uptake and the sustained metabolism of tocotrienols (T3) demonstrate the need for a prompt detoxification of this class of lipophilic vitamers, and thus the potential for cytotoxic effects in hepatic and extra-hepatic tissues. Hypomethylated (γ and δ) forms of T3 show the highest in vitro and in vivo metabolism and are also the most potent natural xenobiotics of the entire vitamin E family of compounds. These stimulate a stress response with the induction of detoxification and antioxidant genes. Depending on the intensity of this response, these genes may confer cell protection or alternatively they stimulate a senescence-like phenotype with cell cycle inhibition or even mitochondrial toxicity and apoptosis. In cancer cells, the uptake rate and thus the cell content of these vitamers is again higher for the hypomethylated forms, and it is the critical factor that drives the dichotomy between protection and toxicity responses to different T3 forms and doses. These aspects suggest the potential for marked biological activity of hypomethylated "highly metabolized" T3 that may result in cytoprotection and cancer prevention or even chemotherapeutic effects. Cytotoxicity and metabolism of hypomethylated T3 have been extensively investigated in vitro using different cell model systems that will be discussed in this review paper as regard molecular mechanisms and possible relevance in cancer therapy.

Tocotrienamines and tocopheramines: reactions with radicals and metal ions.

The antioxidant activity of vitamin E (VE) homologs α, γ and δ-tocotrienamines (4b-6b), never studied before, and α, γ and δ-tocopheramines (4a-7a) was investigated by means of different total antioxidant capacity (TAC) tests. In all the test model systems, compounds 4a-7a and 4b-6b showed similar or higher TAC values than the parental vitamin E forms and their physiological metabolites. α-Homologs of VE amines showed markedly higher activity than the VE congeners in the TEAC test, which is tailored for liposoluble antioxidants, while γ-homologs of the amine analogs showed higher activity in the FRAP tests. Kinetics analysis of the reaction with DPPH(·) showed higher second order rate k for 4a than for α-tocopherol (1a). α-Tocopherolquinone 1f was the common main oxidation product for both 1a and α-tocopheramine (4a) exposed to ferric ions or DPPH(·), and the implied oxidative deamination of 4a was accompanied by a nitration reaction of phenolic substrates that were added to the reaction medium. Possible mechanisms of these reactions were studied.

Immobilization of matrix metalloproteinase 8 (MMP-8) for online drug screening.

Matrix metalloproteinase 8 (MMP-8) has been reported to have a key role in several pathologic conditions, like heart diseases, osteoarthritis, multiple sclerosis, and various other inflammatory conditions. Therefore, there is a great interest regarding the development of MMP-8 selective inhibitors. In the recent years, immobilized enzyme reactors (IMERs) proved to be an efficient alternative to solution-based assays. Besides the recycling of the enzyme, IMER approach allows a simple way to determine affinity data and thus the ranking of inhibiting potency of the compounds under study, especially when coupled to MS. In this study, the immobilization of MMP-8 was investigated in terms of type of support, kinetic parameters, storage and pH stability. Epoxy activated silica resulted the best matrix for the preparation of an immobilized enzyme reactor (IMER) containing human MMP-8. The IMER was successfully used for the online screening of known MMP-8 inhibitors in zonal chromatography and inhibition experiments.

Application of hyphenated mass spectrometry techniques for the analysis of urinary free glucocorticoids.

Alteration of levels of glucocorticoids in plasma and urine can be related to several diseases. In particular, the determination of endogenous glucocorticoids in urine has been reported to provide information on cortisol and cortisone status, on the activities of steroid hormone enzymes and on glucocorticoid metabolism. In this study, the application of hyphenated mass spectrometry techniques (GC/MS without derivatization and LC/MS) for the simultaneous analysis of free urinary cortisol (F), cortisone (E), tetrahydrocortisol (THF), allo-tetrahydrocortisol (A-THF) and tetrahydrocortisone (THE) was evaluated. A sample preparation protocol by solid-phase extraction, mass spectrometry parameters and chromatographic conditions for both techniques were carefully optimized in terms of extracting phase and solvents, matrix effects, recovery, sensitivity and compound resolution. Baseline separation was achieved for the five underivatized analytes both in GC and LC. The LC/MS/MS technique was more suitable for the analysis of urine samples, being less influenced by matrix effects and showing excellent sensitivity and selectivity. A preliminary application of the reported method for the diagnosis of metabolic diseases was also described. The determination of each analyte in its free form, described for the first time in the paper, offers new perspectives in the application of glucocorticoid analysis for diagnostic purposes.

Configuration of the vitamin E analogue garcinoic acid extracted from Garcinia Kola seeds.

Vitamin E derivatives bearing a carboxylic group have recently gained great attention because of their antitumoral properties. Garcinoic acid (trans-13'-carboxy-delta-tocotrienol) is a vitamin E analog extracted from Garcinia Kola seeds in which the carboxylic group is at the end of the aliphatic side chain and reported to be a racemate based on the optical rotation measurements. However, CD determination of a sample of the acid analyzed by us gave a positive peak at 208 nm, indicating that it is not a racemate. To assess the enantiomeric composition of garcinoic acid, it was thus transformed to alpha-tocopherol and analyzed by chiral HPLC on column OD-H. On the basis of the elution order of alpha-tocopherol stereoisomers, the garcinoic acid sample resulted to be enantiopure with R configuration at carbon 2 of the chroman ring. Moreover, in a preliminary test, the acid and some of its derivatives showed a marked antiproliferative effect on glioma C6 cancer cells.

Circular dichroism of tocopherols versus tocotrienols.

Vitamin E is an essential nutrient of still increasing economic importance. Vitamin E derivatives include many nonracemic chiral compounds whose chirooptical characterization is scarcely described in the literature. We report the CD spectra of delta-tocopherol and its unsaturated analog delta-tocotrienol. TDDFT calculations demonstrate that the weak CD of delta-tocopherol is determined by the helicity of dihydropyrane ring. In addition, the moderate CD of delta-tocotrienol is due to the exciton interaction between the aromatic ring and the closest alkene group. Direct exciton-coupled CD calculations on structures generated by two different conformational sampling approaches reveal that, although such exciton coupling is expected to be weak, it is sufficient to explain the spectral differences between tocopherol and tocotrienol.

Vitamin E chemistry. Studies into initial oxidation intermediates of alpha-tocopherol: disproving the involvement of 5a-C-centered "chromanol methide" radicals.

Contrary to concepts handed down in the literature from the early days of vitamin E research, one-electron oxidation of vitamin E does not involve 5a-C-centered radicals. A combined approach of analytical techniques, in particular electron paramagnetic resonance spectroscopy (EPR), organic synthesis of special derivatives, isotopic labeling, kinetic studies, and computational chemistry was used to re-evaluate the one-electron and two-electron oxidation chemistry of alpha-tocopherol (alpha-toc). EPR in combination with 5a-13C-labeled compounds provided no indication of the involvement of 5a-C-centered radicals. Oxidation of special tocopherol derivatives were used to disprove the occurrence of 5a-C-centered one-electron intermediates. Additionally it was shown that those vitamin E reactions that were commonly evoked to plead for the involvement of C-centered tocopheryl radicals actually proceeded via heterolytic, i.e., non-radical, intermediates. The results will help to clear widely spread misunderstandings about the chemistry of vitamin E and will have mechanistic implications for the synthesis of tocopherol-based supramolecular structures and 5a-substituted alpha-tocopherol derivatives.

Identification of 9(E),11(E)-18:2 fatty acid methyl ester at trace level in thermal stressed olive oils by GC coupled to acetonitrile CI-MS and CI-MS/MS, a possible marker for adulteration by addition of deodorized olive oil.

The olive oil market is suffering from sophisticated illegal treatments. One common adulteration process consists of the addition to virgin olive oil of lower quality oils, such as "lampante" oil, an inexpensive oil and with some organoleptic defects, which is then submitted to thermal deodorization under vacuum processes for removal of the undesired flavor components. Such a blending may not have a huge influence on the chemical composition and may not significantly affect the parameters usually checked as quality indicators, although the organoleptic properties may change. As a consequence, a major effort is being devoted to find reliable markers able to unmask such adulterations. We report here the complete characterization of a compound, detected at trace levels exclusively in thermal stressed oils, which could be a candidate marker for adulteration. The investigation, carried out by GC-MS and GC-MS/MS, provided its complete structure, including the stereochemistry, shown to be a 9(E),11(E)-18:2 fatty acid methyl ester. Experimental data also confirmed the influence of both temperature and heating time on formation and concentration of this compound.

First synthesis of rac-(5-2H3)-alpha-CEHC, a labeled analogue of a major vitamin E metabolite.

Over the past few years, quantitative determination of alpha- and gamma-CEHC, main urinary metabolites of vitamin E, has been becoming more and more important as a key parameter in assessing oxidative stress and supplementation of tocopherols. The use of deuterated analogues of these metabolites allows their accurate determination even in complex matrixes. While preparation of gamma-CEHC-d(2) has already been described, here we report the first synthesis of alpha-CEHC-d(3) together with alpha-tocopheronolactone-d(3), its oxidation product.