Determination of lipoic acid, Trolox methyl ether and tocopherols in human plasma by liquid-chromatography and ion-trap tandem mass spectrometry

A method for the simultaneous determination of lipoic acid and/or Trolox methyl ether, along with α‐, γ‐ and δ‐tocopherol was developed using liquid chromatography–tandem mass spectrometry with negative electrospray ionization (HPLC‐ESI‐MS/MS) in an ion‐trap mass spectrometer. Detection and quantification were accomplished by a multiple reaction monitoring method, using specific transitions from precursor ion to product ion for each analyte. Chromatographic separation was achieved in a 12 min run using a C₁₈‐bonded phase and methanol–aqueous ammonium acetate elution gradient. Linear correlations of the chromatographic peak area (r.u. × s^?1) to the injected amount (ng) gave the slope values (r.u. × s^?1 × ng^?1) 2.34 × 10⁴ for α‐tocopherol, 5.05 × 10⁴ for γ‐tocopherol, 1.27 × 10⁵ for δ‐tocopherol, 8.86 × 10⁵ for lipoic acid and 1.23 × 10⁵ for Trolox methyl ether. The lower limit of quantification ranged between 0.02 and 1.22 ng for Trolox methyl ether and lipoic acid. MS³ experiments of γ‐ and δ‐tocopherol suggest ion‐radical reactions and dependence of the tocopherol fragmentation pattern on the phenolic ring methylation degree. The method is shown to be applicable to measurement of these metabolites in human serum after extraction. Copyright © 2012 John Wiley & Sons, Ltd.     

Petasis three-component coupling reactions of hydrazides for the synthesis of oxadiazolones and oxazolidinones

An application of readily available hydrazides in the Petasis 3-component coupling reaction is presented. An investigation of the substrate scope was performed to establish a general, synthetically useful protocol for the formation of hydrazido alcohols, which were selectively converted to oxazolidinone and oxadiazolone ring systems through triphosgene-mediated cyclization reactions.     

Spectroscopic, structural, and conformational properties of (Z)-4,4,4-trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one, C12H12F3NO3: a trifluoromethyl-substituted β-aminoenone

The (Z)-4,4,4-trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one (C(12)H(12)F(3)NO(3)) compound was thoroughly studied by IR, Raman, UV-visible, and (13)C and (19)F NMR spectroscopies. The solid-state molecular structure was determined by X-ray diffraction methods. It crystallizes in the P2(1)/c space group with a = 12.1420(4) ?, b = 7.8210(3) ?, c = 13.8970(5) ?, β = 116.162(2)°, and Z = 4 molecules per unit cell. The molecule shows a nearly planar molecular skeleton, favored by intramolecular OH···O and NH···O bonds, which are arranged in the lattice as an OH···O bonded polymer coiled around crystallographic 2-fold screw-axes. The three postulated tautomers were evaluated using quantum chemical calculations. The lowest energy tautomer (I) calculated with density functional theory methods agrees with the observed crystal structure. The structural and conformational properties are discussed considering the effect of the intra- and intermolecular hydrogen bond interactions.     

Organocatalytic enantioselective synthesis of 2,3-dihydropyridazines

We have developed an efficient procedure for the easy and straightforward preparation of functionalized dihydropyridazines as highly enantiopure materials by reaction of pyruvaldehyde 2-tosyl hydrazone with a variety of α,β-unsaturated aldehydes using a chiral secondary amine as catalyst. The overall process consists of a cascade reaction involving an initial aza-Michael reaction, in which the stereocentre is installed, followed by an intramolecular aldol reaction/dehydration step.     

Simultaneous analysis of mitotane and its main metabolites in human blood and urine samples by SPE-HPLC technique

Adrenocortical carcinoma (ACC) is a rare malignancy with an incompletely understood pathogenesis and a poor prognosis. The adrenalytic activity of mitotane has made it the most important single drug in the treatment of ACC. Unfortunately, the exact mechanism of mitotane action is still unknown. It is believed that mitotane belongs to the class of drugs that require metabolic transformation by cytochrome P450 for therapeutic action; therefore determination of plasma levels of not only mitotane but also its metabolites would help in carrying out the treatment. The objective of this work was to develop and validate an SPE‐HPLC method for simultaneous determination of mitotane and its metabolites in different biological fluids. The sample preparation consisted of a solid‐phase extraction on a Discovery DSC₁₈ cartridge, while analysis of extracts was performed on a Symmetry C₁₈ column. The usefulness of the proposed method was confirmed by analysis of plasma, red cell and urine samples from patient chronically treated with 1.5 g of mitotane. The patient involved in this study had a high plasma concentration of mitotane and none of the investigated metabolites were found. In order to investigate whether the polymorphism of CYP2C9 and CYP2C19 enzymes could be related to the metabolism of mitotane, RT‐PCR analysis was performed. Copyright © 2012 John Wiley & Sons, Ltd.     

The artemisia L. Genus: a review of bioactive essential oils

Numerous members of the Anthemideae tribe are important as cut flowers and ornamental crops, as well as being medicinal and aromatic plants, many of which produce essential oils used in folk and modern medicine and in the cosmetics and pharmaceutical industry. Essential oils generally have a broad spectrum of bioactivity, owing to the presence of several active ingredients that work through various modes of action. Due to their mode of extraction, mostly by distillation from aromatic plants, they contain a variety of volatile molecules such as terpenes, phenol-derived aromatic and aliphatic components. The large genus Artemisia L., from the tribe Anthemideae, comprises important medicinal plants which are currently the subject of phytochemical attention due to their biological and chemical diversity. Artemisia species, widespread throughout the world, are one of the most popular plants in Chinese traditional preparations and are frequently used for the treatment of diseases such as malaria, hepatitis, cancer, inflammation and infections by fungi, bacteria and viruses. Extensive studies of the chemical components of Artemisia have led to the identification of many compounds as well as essentials oils. This review summarizes some of the main reports on the chemistry and anti-infective activities of Artemisia. Li. essential oils from the data in the recent literature (2000-2011).     

Highly stereoselective synthesis of tertiary propargylic centers and their isomerization to enantiomerically enriched allenes

Center of attention: A new approach for the synthesis of enantiomerically enriched allenes by isomerization of 2-p-tolylsulfinylphenyl propargylic derivatives is presented, which in turn are prepared by reaction of sulfinylated lithium benzylcarbanions with arylsulfonylacetylenes. The high control of stereoselectivity in both steps is exerted by the sulfinyl group.     

Surfactant (bi)layers on gold nanorods

Gold nanorods in aqueous solution are generally surrounded by surfactants or capping agents. This is crucial for anisotropic growth during synthesis and for their final stability in solution. When CTAB is used, a bilayer has been evidenced from analytical methods even though no direct morphological characterization of the precise thickness and compactness has been reported. The type of surfactant layer is also relevant to understand the marked difference in further self-assembling properties of gold nanorods as experienced using 16-EO(1)-16 gemini surfactant instead of CTAB. To obtain a direct measure of the thickness of the surfactant layer on gold nanorods synthesized by the seeded growth method, we coupled TEM, SAXS, and SANS experiments for the two different cases, CTAB and gemini 16-EO(1)-16. Despite the strong residual signal from micelles in excess, it can be concluded that the thickness is imposed by the chain length of the surfactant and corresponds to a bilayer with partial interdigitation.     

Interaction of a Rhodococcus sp. trehalose lipid biosurfactant with model proteins: thermodynamic and structural changes

One major application of surfactants is to prevent aggregation during various processes of protein manipulation. In this work, a bacterial trehalose lipid (TL) with biosurfactant activity, secreted by Rhodococcus sp., has been identified and purified. The interactions of this glycolipid with selected model proteins have been studied by using differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, isothermal titration calorimetry (ITC), and fluorescence spectroscopy. Bovine serum albumin (BSA) and cytochrome c (Cyt-c) have been chosen because of their quite different secondary structures: BSA contains essentially no β-sheets and an average 66% α-helix, whereas Cyt-c possesses up to 25% β-sheets and up to 45% α-helical structure. Differential scanning calorimetry shows that addition of TL to BSA at concentrations below the critical micelle concentration (cmc) shifts the thermal unfolding temperature to higher values. FTIR indicates that TL does not alter the secondary structure of native BSA, but the presence of TL protects the protein toward thermal denaturation, mainly by avoiding formation of β-aggregates. Studies on the intrinsic Trp fluorescence of BSA show that addition of TL to the native protein results in conformational changes. BSA unfolding upon thermal denaturation in the absence of TL makes the Trp residues less accessible to the quencher, as shown by a decrease in the value of Stern-Volmer dynamic quenching constant, whereas denaturation in the presence of the biosurfactant prevents unfolding, in agreement with FTIR results. In the case of Cyt-c, interaction with TL gives rise to a new thermal denaturation transition, as observed by DSC, at temperatures below that of the native protein, therefore facilitating thermal unfolding. Binding of TL to native BSA and Cyt-c, as determined by ITC, suggests a rather nonspecific interaction of the biosurfactant with both proteins. FTIR indicates that TL slightly modifies the secondary structure of native Cyt-c, but protein denaturation in the presence of TL results in a higher proportion of β-aggregates than in its absence (20% vs 3.9%). The study of Trp fluorescence upon TL addition to Cyt-c results in a completely opposite scenario to that described above for BSA. In this case, addition of TL considerably increases the value of the dynamic quenching constant, both in native and denatured protein; that is, the interaction with the glycolipid induces conformational changes which facilitate the exposure of Trp residues to the quencher. Considering the structures of both proteins, it could be derived that the characteristics of TL interactions, either promoting or avoiding thermal unfolding, are highly dependent on the protein secondary structure. Our results also suggest the rather unspecific nature of these interactions. These might well involve protein hydrophobic domains which, being buried into the protein native structures, become exposed upon thermal unfolding.