Simultaneous determination of Fe(III) and Al(III) by first-derivative spectrophotometry and partial least-squares (PLS-2) method – Application to post-haemodialysis fluids

Derivative spectrophotometry (graphical method) and partial least-squares regression (numerical method) methods were developed for the spectrophotometric multi-component analysis of post-haemodialysis fluids and synthetic mixtures containing Al(III) and Fe(III) without any chemical separation. The complexes of these metal ions with chrome azurol S were formed immediately at pH 5.5 and were stable for at least 3h. The graphical method is based on the use of first-derivative spectra for evaluation because working wavelength determination was more precise and spectral overlap was less than in the ordinary spectra. Two wavelengths at which the complexes exhibited maximum absorption values for Fe(III) and Al(III) were selected as analytical wavelengths, i.e., 675 and 623.5nm, respectively. Lambert-Beer's law is obeyed between 0.0896-8.064mug/mL Fe(III) and 0.054-0.486mug/mL Al(III). Limits of detection for Fe(III) and Al(III) were 0.056 and 0.044mug/mL, respectively. The reproducibility, expressed as variation coefficients, for two sets of 10 standard mixtures containing 3.584mug/mL Fe(III) and 0.27mug/mL Al(III) were 1.9% and 2% for iron and aluminium, respectively. In the numerical method, a training set was randomly prepared by using 14 samples. The concentration of each component has been varied in the linear range of the analytical signal. The spectral regions between 510 and 720nm were selected for the analysis of the binary mixture of Fe(III)/Al(III). The proposed methods were validated by using synthetic binary mixtures and applied to the simultaneous determination of Fe(III) and Al(III) in post-haemodialysis samples. The obtained results were compared with each other; in general, both multi-component methods gave rise to similar recovery results for laboratory-prepared mixtures and real samples.     

Preparation of an immobilized–stabilized catalase derivative from Aspergillus niger having its multimeric structure stabilized: The effect of Zn on enzyme stability

Multimeric catalase from Aspergillus niger was immobilized on CNBr activated agarose, increasing the enzyme stability. However, it was found that some enzyme subunits could be desorbed to the supernatant after boiling the enzyme preparation in the presence of SDS or during thermal inactivation. Moreover, a positive enzyme concentration-enzyme stability correlation was detected in the immobilized preparation. This suggested the existence of some dissociation mechanism as a first step in the enzyme inactivation. The treatment of the immobilized enzyme with aldehyde–dextran permitted to fully stabilize its multimeric structure, but even this preparation exhibited an enzyme concentration-stability correlation. The presence of EDTA reduced the enzyme stability, suggesting that some cation could be involved in enzyme stability. It was found that 10 mM Zn²⁺ increased the enzyme stability of this immobilized–stabilized preparation. Now, the dilution of the biocatalyst did not produce a reduction in the enzyme stability.Thus, we have prepared an immobilized enzyme that does not release any subunit to the medium even after inactivation, and found that Zn²⁺ has a very positive effect on the stability of this immobilized–stabilized enzyme.     

Combined effects of NaCl and Cd2+ stress on the photosynthetic apparatus of Thellungiella salsuginea

Plants show complex responses to abiotic stress while, the effect of the stress combinations can be different to those seen when each stress is applied individually. Here, we report on the effects of salt and/or cadmium on photosynthetic apparatus of Thellungiella salsuginea. Our results showed a considerable reduction of plant growth with some symptoms of toxicity, especially with cadmium treatment. The structural integrity of both photosystems (PSI and PSII) was mostly maintained under salt stress. Cadmium induced a considerable decrease of both PSI and PSII quantum yields and the electron transport rate ETR(I) and ETR(II) paralleled by an increase of non-photochemical quenching (NPQ). In addition, cadmium alone affects the rate of primary photochemistry by an increase of fluorescence at O-J phase and also the photo-electrochemical quenching at J-I phase. A positive L-band appeared with (Cd) treatment as an indicator of lower PSII connectivity, and a positive K-band reflecting the imbalance in number of electrons at donor and acceptor side. In continuity to our previous studies which showed that NaCl supply reduced Cd²⁺ uptake and limited its accumulation in shoot of divers halophyte species, here as a consequence, we demonstrated the NaCl-induced enhancement effect of Cd²⁺ toxicity on the PSII activity by maintaining the photosynthetic electron transport chain as evidenced by the differences in ψ_O, φ_Eo, ABS/RC and TR₀/RC and by improvement of performance index PI_(ABS), especially after short time of treatment. A significant decrease of LHCII, D1 and CP47 amounts was detected under (Cd) treatment. However, NaCl supply alleviates the Cd²⁺ effect on protein abundance including LHCII and PSII core complex (D1 and CP47).     

Characterization of a nontoxic pyomelanin pigment produced by the yeast Yarrowia lipolytica

In this study, we report on the ability of the yeast Yarrowia lipolytica W29 to produce an extracellular melanin-like brown pigment at high yield (0.5 mg/ml) in culture medium supplemented with L-tyrosine. This pigment has been characterized as pyomelanin and its synthesis was found to occur by the so-called HGA-melanin pathway. The purified pyomelanin was found embedded with antioxidant properties as it exhibited a radical scavenging activity toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) with IC₅₀ of 230 μg/ml. It was also characterized as noncytotoxic toward two mammalian cell lines, namely the mouse fibroblast NIH3T3 and human keratinocytes HaCaT. When blended with different commercial sunscreens, the purified pyomelanin increased significantly the sun protection factor (SPF) value, highlighting its potential utilization as UV-filter in cosmetic preparations.     

Chemical Composition and Cytotoxic Activity of Eucalyptus torquata Luehm. and Eucalyptus salmonophloia F. Muell. Trunk Bark Essential Oils against Human SW620 and MDA-MB-231 Cancer Cell Lines

In recent years, there has been a growing interest in the screening of natural active ingredients from Eucalyptus essential oils because of their evident importance in practical utility and their undeniable therapeutic properties. Based on this, the aim of the present study was to investigate the chemical profile of the essential oils of the trunk bark of Eucalyptus torquata Luehm. (ETEO), and E. salmonophloia F. Muell. (ESEO), growing in Tunisia. The in vitro cytotoxic properties of the extracted EOs were also evaluated against two human cancer cell lines: breast carcinoma cell lines MDA-MB-231 and colorectal cancer cell lines SW620. The analysis by gas chromatography coupled with mass spectrometry (GC/MS) led to the identification of 32 compounds from the ETEO, with the dominant constituents being the monoterpenes trans-myrtanol (73.4 %) and myrtenol (4.7 %), and the apocarotene (E)-β-ionone (3.9 %). In the case of ESEO, 29 compounds were identified with trans-myrtanol (25.0 %), decanoic acid (22.1 %), nonanoic acid (9.8 %), γ-elemene (6.5 %), γ-maaliene (5.5 %), and α-terpineol (5.3 %) as the main components. The cytotoxicity of EOs against the two chosen cell lines was tested using Crystal Violet Staining (CVS) assay and 5-fluorouracil as a reference drug. The two EOs exhibited a significant dose-dependent inhibition against the viability of the used cell lines. Their inhibitory effects were particularly observed towards SW620 colon carcinoma cells with IC₅₀ values of 26.71±1.22 and 22.21±0.85 μg/mL, respectively, indicating that both oils were more cytotoxic for SW620 cells compared to MDA-MB-231 one.