Development of a Two-Dimensional Supercritical Fluid Chromatography System in Multiple Heart-Cutting Modes.

In this study, we present the development of a loop-based two-dimensional supercritical fluid system in multiple heart-cutting modes (mSFC-SFC), with diode-array and mass spectrometric detection. The instrument design was developed to be as simple as possible, based on a single SFC instrument, with the sole addition of three external 2-port 6-position valves. The objective was to achieve the most complete transfer of a peak from the first to the second dimension, whatever the composition of the mobile phase, i.e., whatever the proportion of carbon dioxide and methanol cosolvent along a wide gradient elution. Thanks to fine adjustment of the valve switching times, the first-dimension peaks were parked in 50 µL or 100 µL loops and later discharged to the second dimension. The interest of this instrument was then demonstrated with a sample application on a natural product: an extract of Citrus aurantium L. bark was analyzed, with a particular focus on chiral flavonoids, neohesperidin, and naringin. In this system, the first dimension was an achiral separation of the flavonoids, based on a polar diethylamine-bonded silica stationary phase (ACQUITY Torus DEA), while the second dimension used a stereoselective polysaccharide stationary phase (CHIRALPAK IB-3) to resolve flavonoid diastereomers. Excellent repeatability was demonstrated, with relative standard deviation values on retention times and peak areas all below 2%, together with excellent peak capacity and peak shapes (no distortion observed), making it possible to quantify diastereomers in the second-dimension separation. This good repeatability was also shown for the transfer rate between the two dimensions, which reached a value of 83%. Finally, transferring a compressible sample from the first to the second dimension is demonstrated to yield excellent performance, despite the large loop volume.

Effects of wheat bran extract containing arabinoxylan oligosaccharides on gastrointestinal parameters in healthy preadolescent children.

OBJECTIVES: We assessed whether wheat bran extract (WBE) containing arabinoxylan-oligosaccharides (AXOS) elicited a prebiotic effect and modulated gastrointestinal (GI) parameters in healthy preadolescent children upon consumption in a beverage. METHODS: This double-blind randomized placebo-controlled crossover trial evaluated the effects of consuming WBE at 0 (control) or 5.0 g/day for 3 weeks in 29 healthy children (8-12 years). Fecal levels of microbiota, short-chain fatty acids, branched-chain fatty acids, ammonia, moisture, and fecal pH were assessed at the end of each treatment and at the end of a 1-week run-in (RI) period. In addition, the subjects completed questionnaires scoring distress severity of 3 surveyed GI symptoms. Finally, subjects recorded defecation frequency and stool consistency. RESULTS: Nominal fecal bifidobacteria levels tended to increase after 5 g/day WBE consumption (P = 0.069), whereas bifidobacteria expressed as percentage of total fecal microbiota was significantly higher upon 5 g/day WBE intake (P = 0.002). Additionally, 5 g/day WBE intake induced a significant decrease in fecal content of isobutyric acid and isovaleric acid (P < 0.01), markers of protein fermentation. WBE intake did not cause a change in distress severity of the 3 surveyed GI symptoms (flatulence, abdominal pain/cramps, and urge to vomit) (P > 0.1). CONCLUSIONS: WBE is well tolerated at doses up to 5 g/day in healthy preadolescent children. In addition, the intake of 5 g/day exerts beneficial effects on gut parameters, in particular an increase in fecal bifidobacteria levels relative to total fecal microbiota, and reduction of colonic protein fermentation.

On-line reversed-phase liquid chromatography x supercritical fluid chromatography coupled to high-resolution mass spectrometry: A powerful tool for the characterization of advanced biofuels.

Bio-oils obtained by thermochemical or biochemical conversion of biomass represent a promising source of energy to complement fossil fuels, in particular for maritime or air transport for which the use of hydrogen or electricity appears complicated. As these bio-oils are very rich in water and heteroatoms, additional treatments are necessary before they can be used as biofuel. In order to improve the efficiency of these treatments, it is important to have a thorough knowledge of the composition of the bio-oil. The characterization of bio-oils is difficult because they are very complex mixtures with thousands of compounds covering a very wide range of molecular weight and polarity. Due to the high degree of orthogonality between the two chromatographic dimensions, the on-line combination of reversed-phase liquid chromatography and supercritical fluid chromatography (on-line RPLC x SFC) can significantly improve the characterization of such complex matrices. The hyphenation was optimized by selecting, in SFC, the stationary phase, the co-solvent, the make-up solvent prior to high resolution mass spectrometry (HRMS) and the injection solvent. Additionally, a new interface configuration is described. Quality descriptors such as the occupation of the separation space, the peak shapes and the signal intensity were considered to determine the optimal conditions. The best results were obtained with bare silica, a co-solvent composed of acetonitrile and methanol (50/50, v/v), a make-up solvent composed of methanol (90%) and water (10%) with formic acid (0.1%), an addition of co-solvent through an additional pump for SFC separation in a 2.1 mm column, and an hydro-organic solvent as injection solvent. The optimized setup was used to analyze two microalgae bio-oils: the full bio-oil coming from hydrothermal liquefaction and Soxhlet extraction of microalgae, and the gasoline cut obtained after distillation of the full bio-oil. Results in on-line RPLC x SFC-qTOF were particularly interesting, with very good peak shapes and high reproducibility. Moreover, the high degree of orthogonality for microalgae bio-oils of RPLC and SFC was highlighted by the very large occupation of the separation space. Isomeric profiles of compound families could be obtained in RPLC x SFC-qTOF and many isomers not separated in SFC alone were separated in RPLC and vice versa, thus showing the complementarity of the two chromatographic techniques.

Consumption of breads containing in situ-produced arabinoxylan oligosaccharides alters gastrointestinal effects in healthy volunteers.

Arabinoxylan oligosaccharides (AXOS) are studied as food compounds with prebiotic potential. Here, the impact of consumption of breads with in situ-produced AXOS on intestinal fermentation and overall gastrointestinal characteristics was evaluated in a completely randomized, double-blind, controlled, cross-over study. Twenty-seven healthy volunteers consumed 180 g of wheat/rye bread with or without in situ-produced AXOS (WR(+) and WR(-), respectively) daily for 3 wk. Consumption of WR(+) corresponded to an AXOS intake of ~2.14 g/d. Refined wheat flour bread without AXOS (W(-)) (180 g/d) was provided during the 3-wk run-in and wash-out periods. At the end of each treatment period, participants collected urine for 48 h as well as a feces sample. Additionally, all participants completed a questionnaire about stool characteristics and gastrointestinal symptoms during the last week of each period. Urinary phenol and p-cresol excretions were significantly lower after WR(+) intake compared to WR(-). Consumption of WR(+) significantly increased fecal total SCFA concentrations compared to intake of W(-). The effect of WR(+) intake was most pronounced on butyrate, with levels 70% higher than after consumption of W(-) in the run-in or wash-out period. Consumption of WR(+) tended to selectively increase the fecal levels of bifidobacteria (P = 0.06) relative to consumption of W(-). Stool frequency increased significantly after intake of WR(+) compared to WR(-). In conclusion, consumption of breads with in situ-produced AXOS may favorably modulate intestinal fermentation and overall gastrointestinal properties in healthy humans.

Effects of a wheat bran extract containing arabinoxylan oligosaccharides on gastrointestinal health parameters in healthy adult human volunteers: a double-blind, randomised, placebo-controlled, cross-over trial.

Wheat bran extract (WBE) is a food-grade soluble fibre preparation that is highly enriched in arabinoxylan oligosaccharides. In this placebo-controlled cross-over human intervention trial, tolerance and effects on colonic protein and carbohydrate fermentation were studied. After a 1-week run-in period, sixty-three healthy adult volunteers consumed 3, 10 and 0 g WBE/d for 3 weeks in a random order, with 2 weeks' washout between each treatment period. Fasting blood samples were collected at the end of the run-in period and at the end of each treatment period for analysis of haematological and clinical chemistry parameters. Additionally, subjects collected a stool sample for analysis of microbiota, SCFA and pH. A urine sample, collected over 48 h, was used for analysis of p-cresol and phenol content. Finally, the subjects completed questionnaires scoring occurrence frequency and distress severity of eighteen gastrointestinal symptoms. Urinary p-cresol excretion was significantly decreased after WBE consumption at 10 g/d. Faecal bifidobacteria levels were significantly increased after daily intake of 10 g WBE. Additionally, WBE intake at 10 g/d increased faecal SCFA concentrations and lowered faecal pH, indicating increased colonic fermentation of WBE into desired metabolites. At 10 g/d, WBE caused a mild increase in flatulence occurrence frequency and distress severity and a tendency for a mild decrease in constipation occurrence frequency. In conclusion, WBE is well tolerated at doses up to 10 g/d in healthy adults volunteers. Intake of 10 g WBE/d exerts beneficial effects on gut health parameters.

Novel fungicidal benzylsulfanyl-phenylguanidines.

A series of substituted benzylsulfanyl-phenylamines was synthesized, of which four substituted benzylsulfanyl-phenylguanidines (665, 666, 667 and 684) showed potent fungicidal activity (minimal fungicidal concentration, MFC ≤ 10 µM for Candida albicans and Candida glabrata). A benzylsulfanyl-phenyl scaffold with an unsubstituted guanidine resulted in less active compounds (MFC=50-100 µM), whereas substitution with an unsubstituted amine group resulted in compounds without fungicidal activity. Compounds 665, 666, 667 and 684 also showed activity against single C. albicans biofilms and biofilms consisting of C. albicans and Staphylococcus epidermidis (minimal concentration resulting in 50% eradication of the biofilm, BEC50 ≤ 121 µM for both biofilm setups). Compounds 665 and 666 combined potent fungicidal (MFC=5 µM) and bactericidal activity (minimal bactericidal concentration, MBC for S. epidermidis ≤ 4 µM). In an in vivo Caenorhabditis elegans model, compounds 665 and 667 exhibited less toxicity than 666 and 684. Moreover, addition of those compounds to Candida-infected C. elegans cultures resulted in increased survival of Candida-infected worms, demonstrating their in vivo efficacy in a mini-host model.

Membrane rafts are involved in intracellular miconazole accumulation in yeast cells.

Azoles inhibit ergosterol biosynthesis, resulting in ergosterol depletion and accumulation of toxic 14alpha-methylated sterols in membranes of susceptible yeast. We demonstrated previously that miconazole induces actin cytoskeleton stabilization in Saccharomyces cerevisiae prior to induction of reactive oxygen species, pointing to an ancillary mode of action. Using a genome-wide agar-based screening, we demonstrate in this study that S. cerevisiae mutants affected in sphingolipid and ergosterol biosynthesis, namely ipt1, sur1, skn1, and erg3 deletion mutants, are miconazole-resistant, suggesting an involvement of membrane rafts in its mode of action. This is supported by the antagonizing effect of membrane raft-disturbing compounds on miconazole antifungal activity as well as on miconazole-induced actin cytoskeleton stabilization and reactive oxygen species accumulation. These antagonizing effects point to a primary role for membrane rafts in miconazole antifungal activity. We further show that this primary role of membrane rafts in miconazole action consists of mediating intracellular accumulation of miconazole in yeast cells.

A fungicidal piperazine-1-carboxamidine induces mitochondrial fission-dependent apoptosis in yeast.

To unravel the working mechanism of the fungicidal piperazine-1-carboxamidine derivative BAR0329, we found that its intracellular accumulation in Saccharomyces cerevisiae is dependent on functional lipid rafts. Moreover, BAR0329 induced caspase-dependent apoptosis in yeast, in which the mitochondrial fission machinery consisting of Fis1 (Whi2), Dnm1 and Mdv1 is involved. Our data are consistent with a prosurvival function of Fis1 (Whi2) and a proapoptotic function of Dnm1 and Mdv1 during BAR0329-induced yeast cell death.

Arabinoxylan-oligosaccharides (AXOS) reduce preneoplastic lesions in the colon of rats treated with 1,2-dimethylhydrazine (DMH).

BACKGROUND: Prebiotics are non-digestible compounds that beneficially affect the host by stimulating the growth and/or activity of one or a limited number of resident colonic bacteria in the gut. Reported beneficial effects of prebiotics include reduced gut infections, better absorption of minerals, and notably, antitumorigenic effects. Arabinoxylan (AX)-oligosaccharides (AXOS) have been suggested to exert prebiotic effects in the gut, but their effect on colon carcinogenesis has not been studied so far. AIM OF THE STUDY: To test the effect of AXOS in a rat colon carcinogenesis model. METHODS: We determined the occurrence of two types of preneoplastic lesions [aberrant crypt foci (ACF) and mucin depleted foci (MDF)] in the colon of rats treated with the colon carcinogen 1,2-dimethylhydrazine (DMH) and fed either a control diet or a diet containing AXOS (4.8% w/w) (15 rats in each group). RESULTS: Thirteen weeks after DMH treatment, MDF counts were significantly lower in the entire colon of AXOS fed rats (MDF/colon were 7.5 +/- 0.6 and 5.5 +/- 0.6, in Control and AXOS groups, respectively, means +/- SE, P < 0.05). Although the number of ACF in the entire colon was not significantly different between Control and AXOS fed rats, AXOS fed rats had significantly fewer ACF in the distal part of the colon than Control group rats (ACF/distal colon were 135.5 +/- 15 and 84.4 +/- 11, in Control and AXOS groups, respectively, means +/- SE, P < 0.05). CONCLUSIONS: The present study shows that dietary intake of AXOS by rats reduces the occurrence of two types of preneoplastic lesions, thus suggesting a chemopreventive effect on colon carcinogenesis that should be confirmed in a long-term carcinogenesis experiment.

Considerations on comprehensive and off-line supercritical fluid chromatography x reversed-phase liquid chromatography for the analysis of triacylglycerols in fish oil.

The separation of the triacylglycerols in fish oil was performed by comprehensive and off-line supercritical fluid chromatography combined with RP-LC. The first dimension consisted of two serially coupled silver-ion (SI)-loaded columns operated with a supercritical mobile phase (supercritical fluid chromatography, SFC) in both the cases, whereas the second dimension was performed in non-aqueous RP mode (NARP-LC) on a 10-cm monolithic octadecyl silica (ODS) or a 45-cm long ODS column packed with 1.8 microm particles for the comprehensive and off-line separations, respectively. Despite the outstanding performance of the SI-SFC x NARP-LC interface, the high complexity of the sample rendered the online separation far from complete. The off-line approach gave much better separation mainly because of the higher peak capacity of the second-dimension column, but even in this case, the use of MS was mandatory to elucidate the different triacylglycerols in fish oil. The disadvantage of the off-line procedure was the long analysis time.

Safety assessment of a wheat bran extract containing arabinoxylan-oligosaccharides: mutagenicity, clastogenicity, and 90-day rat-feeding studies.

Wheat bran extract (WBE) is a food-grade preparation that is highly enriched in arabinoxylan-oligosaccharides. As part of the safety evaluation of WBE, its genotoxic potential was assessed in a bacterial reverse mutagenicity assay (Ames test) and a chromosome aberration assay on Chinese hamster lung fibroblast cells. These in vitro genotoxicity assays showed no evidence of mutagenic or clastogenic activity with WBE. The safety of WBE was furthermore evaluated in a subchronic toxicity study on rats that were fed a semisynthetic diet (AIN 93G) containing 0.3%, 1.5%, or 7.5% WBE for 13 weeks, corresponding to an average intake of 0.2, 0.9, and 4.4 g/kg body weight (bw) per day, with control groups receiving the unsupplemented AIN 93G, AIN 93G with 7.5% inulin, or AIN 93G with 7.5% wheat bran. Based on this rat-feeding study, the no-observed-adverse-effect level (NOAEL) for WBE was determined as 4.4 g/kg (bw)/d, the highest dose tested.

Synthesis and fungicidal activity of 3,5-dichloropyrazin-2(1H)-one derivatives.

We synthesized a family of 3,5-dichloropyrazin-2(1H)-one derivatives and assessed their in vitro fungicidal activity against Candida albicans. Compounds 11 and 20 were most active against C. albicans and induced accumulation of reactive oxygen species in this pathogen. Using a genome-wide approach in the yeast Saccharomyces cerevisiae, we demonstrated that genes involved in vacuolar functionality and DNA-related functions play an important role in cellular mechanisms underlying the fungicidal activity of these compounds.

Tryptic digest analysis by comprehensive reversed phasextwo reversed phase liquid chromatography (RP-LCx2RP-LC) at different pH's.

As an alternative to the classical approach of combining strong cation exchange SCX-LC and RP-LC for the separation of complex proteomic samples, this essay describes the online comprehensive RP-LCxRP-LC separation of BSA and human blood serum. High orthogonality and peak capacity are achieved through the application of a significantly different pH in the two dimensions. The coupling of fused-core columns in series ensures high efficiency in the first dimension, while a previously designed interface with parallel second dimension columns further enhances the separation capability of the comprehensive system.

Selective drug metabolite trace analysis by very high-volume injections and heartcut two-dimensional (2D)-ultrahigh performance liquid chromatography (UHPLC).

The application of two-dimensional liquid chromatography (2D-LC) is gradually growing also in the area of metabolite profiling and identification. The current contribution describes a heartcut 2D-UHPLC configuration that is applied in support of drug metabolism studies in development. The setup applies four LC columns: two analytical UHPLC columns to perform the first and second dimension separations, which are both preceded by a short HPLC column operated as trapping column. The first HPLC column allows a significant online preconcentration by large volume injection. The second short HPLC column is placed between the first and second dimension columns and enables the selection of orthogonal conditions in the second dimension independent of the first dimension making the heartcutting 2D approach more generic. The value of the setup was demonstrated with selective ultraviolet chromatograms obtained for the two major hydroxylated metabolites of atorvastatin separating them from a very high biological background, originating from an injection of 4 mL feces extract, by heartcut 2D-LC. In a second application, the main metabolite of imipramine was baseline separated from some minor metabolites that were co-eluting in the first dimension, allowing accurate and sensitive quantification. A quantification limit in the attogram/mL range was achieved thanks to the injection of 200 mL diluted urine, corresponding to 100 mL urine on column.

In vitro activity of the antifungal plant defensin RsAFP2 against Candida isolates and its in vivo efficacy in prophylactic murine models of candidiasis.

We show that RsAFP2, a plant defensin that interacts with fungal glucosylceramides, is active against Candida albicans, inhibits to a lesser extent other Candida species, and is nontoxic to mammalian cells. Moreover, glucosylceramide levels in Candida species correlate with RsAFP2 sensitivity. We found RsAFP2 prophylactically effective against murine candidiasis.

Low prevalence of HIV and other sexually transmitted infections in young women attending a youth counselling service in Maputo, Mozambique.

OBJECTIVES: To determine the prevalence of sexually transmitted infections (STIs) in a group of young women attending the Adolescent and Youth Friendly Service, in Maputo, Mozambique, and to evaluate their level of knowledge, practices and attitudes about STI. METHODS: A total of 445 women voluntarily participated in the study and filled in a self-administered knowledge, practices and attitudes (KAP) questionnaire; 435 of them underwent a laboratory examination for vaginosis, candidiasis, trichomoniasis, gonorrhoea, chlamydiosis, syphilis and HIV infection. RESULTS: Women had a high level of awareness and knowledge of STI and HIV. Candidiasis was the most prevalent reproductive tract infection (36%), followed by vaginosis (13%) and trichomoniasis (7.6%), and sexually transmitted diseases. HIV seroprevalence was 4%; 42% were negative in all tests. CONCLUSION: The low prevalence of STI and HIV may be related in part to the high level of awareness registered in the group.

Fungicidal activity of truncated analogues of dihydrosphingosine.

The minimal fungicidal concentration (MFC) of dihydrosphingosine (DHS), phytosphingosine (PHS), and five short-chain DHS derivatives was determined for Candida albicans and Candida glabrata. In this respect, a C15- and a C17-homologue of DHS showed a 2- to 10-fold decreased MFC as compared to native DHS (i.e. C18-DHS). DHS derivatives that were active, that is, comprising 12, 15, 17, or 18 carbon atoms, induced accumulation of reactive oxygen species (ROS) in C. albicans.

Comprehensive two-dimensional liquid chromatography applying two parallel columns in the second dimension.

The design of a new interface for comprehensive two-dimensional liquid chromatography (LC x LC) is described. To the conventionally used LC x LC system with the loop-type interface consisting of a two-position/ten-port switching valve equipped with two loops, an extra two-position/ten-port switching valve, a detector, a pump and a second column placed in parallel with the column in the second dimension, are added. The features of the interface are that the separation space in the second dimension is significantly enlarged and that the number of fractions transferred from the first to the second dimension can be increased, reducing the risk to lose resolution of the primary dimension. The potential of the system in NPLC x 2RPLC is illustrated with the analysis of a standard mixture and a lemon oil extract. For the lemon oil analysis, the effective peak capacity was increased from 437 using a conventional interface to 1095 with the new interface. RPLC x 2RPLC in combination with reduced modulation times was applied to the analysis of steroids and to the detection of impurities at the 0.05% relative concentration level in a sulfonamide drug sample.

Construction of a new interface for comprehensive supercritical fluid chromatography x reversed phase liquid chromatography (SFC x RPLC).

The design of a new interface to hyphen high efficiency supercritical fluid chromatography (SFC) and fast RPLC in a comprehensive configuration is described. SFC x RPLC is a viable alternative to normal phase (NP) LC x RPLC and is characterized by high orthogonality. Compared to NPLC x RPLC an additional advantage is the expansion of supercritical carbon dioxide (CO(2)) when exposed to atmospheric pressure leading to fractions consisting of solvents that are miscible with the second dimension RPLC mobile phase. The interface consists of a two-position/ten-port switching valve equipped with two packed octadecyl silica (C(18)) loops for effective trapping and focusing of the analytes after elution from the SFC dimension. The addition of a water make-up flow to the SFC effluent prior to entering the loops is of fundamental importance to efficiently focus the solutes on the C(18) material and to reduce interferences of expanded CO(2) gas on the second dimension separation. The features of the system are illustrated with the analysis of a lemon oil sample.

First inter-laboratory study of a Supercritical Fluid Chromatography method for the determination of pharmaceutical impurities.

Supercritical Fluid Chromatography (SFC) has known a strong regain of interest for the last 10 years, especially in the field of pharmaceutical analysis. Besides the development and validation of the SFC method in one individual laboratory, it is also important to demonstrate its applicability and transferability to various laboratories around the world. Therefore, an inter-laboratory study was conducted and published for the first time in SFC, to assess method reproducibility, and evaluate whether this chromatographic technique could become a reference method for quality control (QC) laboratories. This study involved 19 participating laboratories from 4 continents and 9 different countries. It included 5 academic groups, 3 demonstration laboratories at analytical instrument companies, 10 pharmaceutical companies and 1 food company. In the initial analysis of the study results, consistencies within- and between-laboratories were deeply examined. In the subsequent analysis, the method reproducibility was estimated taking into account variances in replicates, between-days and between-laboratories. The results obtained were compared with the literature values for liquid chromatography (LC) in the context of impurities determination. Repeatability and reproducibility variances were found to be similar or better than those described for LC methods, and highlighted the adequacy of the SFC method for QC analyses. The results demonstrated the excellent and robust quantitative performance of SFC. Consequently, this complementary technique is recognized on equal merit to other chromatographic techniques.