Sum Of Mg Research Articles

Undervalued Atlantic brown seaweed species (Cystoseira abies-marina and Zonaria tournefortii): influence of treatment on their nutritional and bioactive potential and bioaccessibility

The brown seaweed species Cystoseira abies-marina and Zonaria tournefortii are abundant Atlantic resources that remain undervalued. This results from an insufficient knowledge of their nutrients’ and bioactive potential. There is also uncertainty regarding the adequate culinary treatment of these seaweeds prior to their consumption. Thus, the current study evaluated the composition, bioactivity, and bioaccessibility of target compounds and bioactivities of these two species as a function of two treatments, simple rehydration and steaming, in comparison to sun-dried seaweed. The proportion of SFA, MUFA, and PUFA differed between species. C. abies-marina was richer in PUFA (30–31% vs 20–21%) and Z. tournefortii was richer in SFA (53–57% vs 46–47%). Main contributors to ω3 PUFA content were different in each species: alpha-linolenic acid in C. abies-marina, 4.5–5.1%, and eicosapentaenoic acid in Z. tournefortii, 5.8–6.7%. The sum of Mg and Ca contents in Z. tournefortii was two-fold the same sum in the other species. Furthermore, rehydration led to an elemental concentration reduction in most instances. The As content in C. abies-marina was very high, ranging between 295 ± 5 mg/kg dw and 369 ± 2 mg/kg dw, in rehydrated and steam-cooked seaweed, respectively. While aqueous extracts of C. abies-marina had the highest phenolic contents, 620–1280 mg GAE/100 g dw, aqueous extracts of Z. tournefortii contained 170–280 mg GAE/100 g dw. Regarding bioaccessibility, Mg, K, Ca, As, and Cd showed relatively high bioaccessibility levels and it was shown that only a limited part of the original antioxidant activity in both species is bioaccessible.

Solid base Mg-doped ZnO for heterogeneous catalytic ozonation of isoniazid: Performance and mechanism

Magnesium-doped ZnO (denoted as x-MgZnO where x represented the molar ratio of Mg to the sum of Mg and Zn) powders synthesized by the traditional thermal decomposition were used as catalysts for ozonation of isoniazid (20 mg/L) at the initial pH of 7.2. Magnesium substituted zinc in wurtzite structure and the Zn—O—Mg bond was formed in Mg-doped ZnO on the basis of the results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. The removal efficiencies of isoniazid were enhanced in Mg-doped ZnO catalytic ozonation processes (57.7% by 0.05-MgZnO and 76.3% by 0.10-MgZnO in 9 min), compared with ozonation alone (50.5%) and ZnO catalytic ozonation (49.5%). The removal efficiencies of total organic carbon (TOC) were also improved in Mg-doped ZnO catalytic ozonation processes. When the initial pH of 7.2 was lower than the pHPZC (point of zero charge) of Mg-doped ZnO, surface hydroxyl groups of the catalysts were protonated and the solution pH gradually increased during Mg-doped ZnO catalytic ozonation. The increase in the solution pH value mainly induced ozone decomposition into superoxide radical (O2–). Furthermore, protonated surface hydroxyl groups (S-OH2+) on Mg-doped ZnO also contributed a little to ozone decomposition. The 0.10-MgZnO powder showed high stability after continuous use in the process. Additionally, we proposed a possible degradation pathway for the oxidation of isoniazid in Mg-doped ZnO catalytic ozonation on the basis of intermediates detected. This work provides an insight into the mechanism for basic sites of solid base in heterogeneous catalytic ozonation.

Modelling the long-term feed-to-fillet transfer of leuco crystal violet and leuco malachite green in Atlantic salmon (Salmo salar)

ABSTRACTLeuco crystal violet (LCV) and leuco malachite green (LMG) are the main metabolites of two dyes that are forbidden for use in food production, but can be present at low background concentration in novel Atlantic salmon feed ingredients such as processed animal proteins (animal by-product [ABP]). In this study, the potential transfer of dietary LCV or LMG to the fillet of farmed Atlantic salmon was investigated. The uptake and elimination rate kinetics were determined in seawater-adapted Atlantic salmon (initial weight 587 ± 148 g) fed two levels of either LCV- or LMG-enriched diets (~500 and 4000 µg kg−1, respectively) for 40 days, followed by a 90-day depuration period with feeding on control diets (<0.15 μg kg−1 LCV and LMG). A three-compartmental model was developed, based on a fillet fat, fillet muscle and a central body compartment comprising all other tissues. Model calibrations showed a good fit with measured values during overall uptake and elimination period; however, the model poorly predicted the short-term (days) peak measured values at the end of the exposure period. The model was used to simulate the long-term (>16 months) LCV and LMG feed-to-fillet transfer in Atlantic salmon under realistic farming conditions such as the seasonal fluctuations in feed intake, growth and fillet fat deposition. The model predictions gave highest expected LCV and LMG fillet concentrations of approximately 0.12 and 0.45 μg kg−1, depending on the dietary levels of ABP and background level of LCV and LMG contamination. These levels are under the reference point for action of 2 µg kg−1 for the sum of MG and LMG that EFSA assessed as adequate to protect public health. However, for LCV, the predicted highest levels exceed the analytical decision limit (CCα) of 0.15 µg kg−1 for the method used in this paper.

Malachite Green and Leuco-Malachite Green Detection in Fish Using Modified Enzyme Biosensor

A modified enzyme-based biosensor was developed for amperometric measurement of total Malachite Green (sum of MG and LMG) in tilapia fish. The 4 UmL-1 butyrylcholinesterase enzyme (BuChE) was used and immobilized onto the surface of carbon paste electrode during the electro-polymerization of polypyrrole (PPy). It is a simple, rapid and sensitive technique used for determination of total MG using 0.1M phosphate buffer pH 8.0. In this study, butyrylthiocholine iodide (0.3 Mm BTCi) was used as a substrate which produced the thiocholine due to the enzymatic hydrolysis. Then, it was oxidized at 0.4V against silver-silver chloride electrode for 100 s. The modified enzyme biosensor provided a high sensitivity and linear concentration range from 0.25 to 10 ppb with a limit of detection (LOD) at 0.25 ppb. The results showed the linear standard curve of total MG standard solution (based on the current output in microampere) with the equation of y = - 0.9113x + 10.84, R2 = 0.9445.

Liquid chromatography with time-of-flight mass spectrometry for simultaneous determination of chemotherapeutant residues in salmon

Liquid chromatography with time-of-flight mass spectrometry (LC–TOF-MS) method has been developed for simultaneous confirmation by accurate mass measurement and quantitative determination of antibiotics (enrofloxacin, oxolinic acid, flumequine, erythromycin), fungicides (malachite green MG, leucomalachite green LMG) and parasiticide (emamectin benzoate) residues in edible portion of salmon. Confirmation of chemotherapeutant residues has been based on the system of identification points (IPs) established in the Commission Decision 2002/657/EC concerning the use of mass spectrometry (MS) techniques. A validation study on matrix is presented evaluating accuracy in terms of precision ( λ ppm 0.83–1.15) and trueness (0.22–0.70 Da). Limits of detection (LODs) and limits of quantification (LOQs) were in ranges of 1–3 and 3–9 μg/kg, below the maximum residue limits (MRLs) established in current EU legislation (100–200 μg/kg) for these chemotherapeutants. Considering the EU guidelines, decision limits (CCα) and detection capabilities (CCβ) were determined (ranges of 103–218 and 107–234 μg/kg, respectively) for authorised substances. For no authorised compounds (MG and LMG), LODs were 2 and 1 μg/kg, respectively, but exceed the MRPL (minimum required performance limit) established in the legislation which corresponds to the sum of MG and LMG (2 μg/kg). Acceptable intra-day and inter-day variability, in terms of relative standard deviation (R.S.D.) of the analytical method, were obtained (2–15%). Linearity was demonstrated from the LOQs of the analytes to 600 μg/kg ( r > 0.9991). The method has involved an extraction procedure based on solid–liquid extraction (SLE) with recoveries higher than 80% for most target chemotherapeutants, with exception of enrofloxacin (40%).

Geochemical well logging in basalts: The Palisades Sill and the oceanic crust of Hole 504B

Geochemical well logging provides a continuous record of the variations in elemental abundances of the major rock‐forming oxides of Si, Al, Ca, Fe, Ti, and K, as well as S, Gd, U, Th, and the H and Cl in the formation and pore fluid. Through the additional measurement of the photoelectric capture cross section of the rock, the sum of Mg + Na can also be estimated. Though not as accurate as laboratory analyses of recovered core samples, the log‐derived abundances are precise enough to define the degree and extent of alteration, to identify igneous lithostratigraphy, and to calculate integrated chemical exchange between the oceanic crust and seawater. In this paper, the elemental yields from geochemical logging in basalts are calibrated against extensive XRF analyses of cutting samples from the Lamont 2 test well into the diabases of the Palisades Sill, New York. Accuracy and precision of the log‐derived analyses are determined in the lower part of the well, and calibration equations are derived, which are then tested against core‐derived “standards” from the upper part of the well. The calibrated, log‐derived, elemental analyses are within one standard deviation of the core‐derived results (except for the Mg + Na curve, which is somewhat noisier). These calibrations are then applied to geochemical logs from the oceanic crustal basalts of Ocean Drilling Program hole 504B, where core recovery was less than 20% of the section. The accuracy and precision of the calibrated, log‐derived elemental abundances are tested against core‐derived standards from seven dike and sill intervals. Then the corrected elemental analyses are used to derive a mineralogy model for hole 504B that shows the oceanic crust to contain secondary mineralization in the form of celadonites and smectites in the pillow basalts and chlorites in the dikes that are largely confined to fracture and breccia zones. Cyclicity in the Al and other elemental logs was found to vary with the abundances of these alteration products and with eruption and intrusion event boundaries. The geochemical logging data are then used to estimate the integrated chemical exchange resulting from hydrothermal alteration of the oceanic crust that has occurred over the last 5.9 m.y. in hole 504B. The primary change is from Ca loss and Mg gain caused by the reaction of basalt with seawater. A large Si increase found in the transition zone between the pillows and dikes is attributed to precipitation of quartz during mixing of hot, up welling hydrothermal fluids and cold, downwelling seawater at what was once a major permeability discontinuity. The present low‐to‐high permeability transition in hole 504B is found 500 m shallower. The K budget requires significant addition to the uppermost pillow basalts both from high‐temperature depletion in the lower pillows and dikes and from low‐temperature exchange with seawater. The geochemical logs further document that the total chemical exchange between the oceanic crust and seawater is as important to the long‐term composition of the oceans as is the chemical input carried by rivers. Integrated “water/rock ratios” are then derived for the mass of seawater required to add enriched elements and the mass of hydrothermal fluid required to remove depleted elements in the oceanic crust of hole 504B. Whereas Ca, Mg, and K require relatively low water/rock ratios, high values for Si, Al, and Fe suggest that off‐axis, ridge‐flank exchange is as important to the total cation exchange budget as are ridge‐axis processes.

Magnesium-supplying power of some Finnish mineral soils

Uptake of magnesium from a sand, fine sand, muddy clay, silty clay and heavy clay soil under exhaustive cropping with perennial rye grass was studied in green house. An application of 0.5 g Mg as MgSO4 ∙ 7 H2O per the 5-liter pots increased slightly the total yield of rye grass shoots and markedly the amount of Mg harvested in the shoots from the sand and fine sand soils with an initial content of only 14 and 37 ppm exchangeable Mg, respectively. No respond to the application of Mg was detected in the silty clay and heavy clay soils which contained exchangeable Mg 226 and 910 ppm, respectively. The muddy clay soil contained 137 ppm exchangeable Mg, and the application of Mg markedly increased the amount of Mg harvested in the shoots, but brought about a decrease in the yield of shoots. The amount of Mg harvested in the shoots without the application of Mg was only in the sand and fine sand soils higher than the original content of exchangeable Mg. Yet, in all soils except in the muddy clay, the decrease in the content of exchangeable Mg during the cropping was lower than the amount of Mg harvested. This was taken to indicate that some release of nonexchangeable Mg did occur during this trial. According to a rough estimation this mobilization of Mg varied from 0 to 60 ppm, whereas the corresponding release of nonexchangeable K was 500–1000 ppm, except in the sand soil. The »exhaustion Mg», or the sum of Mg harvested in the shoots of rye grass and the exchangeable Mg in the soil after cropping, was in all soils of the same order as the amount of Mg extracted by 0.05 N or 0.1 N HCI from the original soil samples.