A liquid chromatographic method for vitamin K1 in milk-based infant formula is described. The vitamins are extracted from infant formula by matrix solid-phase dispersion and quantitated by reversed-phase chromatography with fluorescence detection. Vitamin K1 is converted to the fluorescent hydroquinone with a postcolumn zinc reductive reactor. The limit of detection is 12 pg, and the limit of quantitation is 38 pg on-column. Linear responses were obtained in the range 0.55-22.1 ng/mL (r2 = 0.9998). Recoveries of vitamin K1 from an analyte-fortified blank material for milk-based infant formula averaged 91.7% (n = 25). The method provides a rapid, specific, and easily controlled assay for vitamin K1 in fortified infant formula.
18Inflammatory diseases of the gut are associated with increased intestinal oxygen 19 concentrations and high levels of inflammatory oxidants, including hydrogen peroxide 20 (H2O2) and hypochlorous acid (HOCl), which are antimicrobial compounds produced by 21 the innate immune system. This contributes to dysbiotic changes in the gut microbiome, 22including increased populations of pro-inflammatory enterobacteria (Escherichia coli 23 and related species) and decreased levels of health-associated anaerobic Firmicutes 24 and Bacteroidetes. The pathways for H2O2 and HOCl resistance in E. coli have been 25 well-studied, but little is known about how commensal and probiotic bacteria respond to 26 inflammatory oxidants. In this work, we have characterized the transcriptomic response 27 of the anti-inflammatory, gut-colonizing Gram-positive probiotic Lactobacillus reuteri to 28 both H2O2 and HOCl. L. reuteri mounts distinct responses to each of these stressors, 29and both gene expression and survival were strongly affected by the presence or 30 absence of oxygen. Oxidative stress response in L. reuteri required several factors not 31 found in enterobacteria, including the small heat shock protein Lo18, polyphosphate 32 kinase 2, and RsiR, an L. reuteri-specific regulator of anti-inflammatory mechanisms. 33These results raise the intriguing possibility of developing treatments for inflammatory 34 gut diseases that could sensitize pro-inflammatory enterobacteria to killing by the 35 immune system while sparing anti-inflammatory, health-associated species. 36 37 IMPORTANCE 38It is becoming increasingly clear that effective treatment of inflammatory gut diseases 39 will require modulation of the gut microbiota. Preventing pro-inflammatory bacteria from 40 blooming while also preserving anti-inflammatory and commensal species is a 41 considerable challenge, but our results suggest that it may be possible to take 42 advantage of differences in the way different species of gut bacteria resist inflammatory 43 oxidants to accomplish this goal. 44 a measurable health benefit (14), and a variety of different probiotic bacteria have been 64shown to have anti-inflammatory effects in the gut (15, 16). The most commonly used 65 probiotics are lactic acid bacteria of the genus Lactobacillus (17), which are able to both 66 modulate the host immune system and outcompete enterobacterial pathogens (15), and 67 some strains of which have been shown to improve outcomes for inflammatory bowel 68 diseases in both humans and animal models (18)(19)(20). The effectiveness of probiotics for 69 treating inflammation in the gut, however, may be limited by their ability to survive attack 70 by the overactive host immune system, including the oxidative damage caused by ROS 71 and RCS. While the general stress response physiology of lactic acid bacteria has been 72 relatively well characterized (21), bacterial responses to oxidative stress are best 73 understood in E. coli and related inflammation-enriched enterobacteria (22)(23)(24)(25). This is 74 esp...
Chemical noise limits mass spectrometric detection of chloramphenicol (CAP) with electron capture ionization at low resolution, and makes CAP identification at concentrations of 5 parts per billion (ppb) difficult. Increasing the resolution from 1000 to 3500, however, was sufficient to separate the analyte signals from the noise signals, and resulted in a 100 times higher analytical sensitivity. The introduction of sweep gas in the ion source decreased the scattering of the quantitative results on average by a factor of 7, and thereby improved the precision of the analyses to an acceptable level (CV < 10%). Under such conditions, CAP residues of 1.5 and 2.1 ppb in shrimp as determined by electron capture gas chromatography/mass spectrometry can readily be identified by monitoring four diagnostic ions.
A liquid chromatographic method is described for analysis of all-rac-α-tocopheryl acetate and retinyl palmitate in medical food. The vitamins are extracted in isopropyl alcohol and hexane-ethyl acetate without saponification and quantitated by normal-phase chromatography with fluorescence detection. All-rac-α-tocopheryl acetate and retinyl palmitate are chromatographed isocratically with a mobile phase of 0.5% (v/v) and 0.125% (v/v) isopropyl alcohol in hexane, respectively. Recovery studies performed on a medical food zero control reference material (ZRM) fortified with the analytes averaged 99.7% (n = 25) for retinyl palmitate and 101% (n = 25) for all-rac-α-tocopheryl acetate. Coefficients of variation were 0.87-2.63% for retinyl palmitate and 1.42-3.20% for all-rac-α-tocopheryl acetate. The method provides a rapid, specific, and easily controlled assay for analysis of vitamin A and vitamin E in medical foods. Use of chlorinated solvents is avoided.
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