Monica Mosca

Effect of membrane composition on lipid oxidation in liposomes.

To study the effect of membrane composition on the oxidation of liposomes, different systems were prepared by adding one component at time to phosphatidylcholine (Epikuron 200). In particular, the effect of cholesterol and its ester, cholesterol stearate, on membrane structure and oxidation was studied. A first screening of the structure and net charge of the different preparation was made by means of z-potential and size measurements. Then the liposomes were oxidized by using a hydrophilic radical initiator, the (2,2-azobis(2-amidinopropane) hydrochloride, AAPH, which thermally decomposes to give a constant radical flux in water. The oxidation of liposomes, monitored by following the absorbance of the primary products of oxidation at 234 nm, was shown to be dependent on the composition of the liposomal bilayer and so on its biophysical properties. In addition, size and z-potential measurements gathered in the time course of the peroxidation reaction, revealed that the oxidation induced a modification of the superficial characteristics of the membrane bilayer so as to change its charge at the shear plane (z-potential). This behaviour was shared by all liposomal preparations independent of the composition. The change in sizes of the different liposomal preparation, instead, followed different trends, being more stable both in control samples and in oxidized ones when cholesterol was present. From the analysis of the results, it can be concluded that cholesterol affects the oxidation induced by hydrophilic radical initiator of model membranes by changing the biophysical properties of the phospholipid bilayer. The rigidity induced by cholesterol at temperatures above the T(m) makes the membrane more resistant to radical attack from an external aqueous phase and this in turn delays the start of the reaction. The decrease of z-potential of the liposomal particles induced by the oxidation process can be an important clue to understand the mechanisms involved in the etiology of important diseases.

Impact of antioxidants dispersions on the stability and oxidation of water-in-olive-oil emulsions

Water-in-olive-oil emulsion stability was studied as a function of the composition of the water dispersed phase. In particular, different polyphenolic extracts from natural sources were dispersed in the olive oil and their impact on emulsion kinetic stability and susceptibility to oxidation was evaluated. As natural sources, extra virgin olive oil, olive mill waste and green tea leaves were chosen. To test their impact on emulsion properties, the emulsions were prepared with fixed aqueous phase content. As emulsifiers, a fixed percentage of a mixture Span 80 (sorbitan monoleate)/Tween 80 (polysorbate 80) was used. The effect of the antioxidant dispersion on emulsion oxidation was studied by triggering the oxidation reaction in the oil phase with the lipophilic radical initiator AMVN (2,2-azobis(2,4-dimethylvaleronitrile). Then, the oxidation reaction was followed by using diphenyl-1-pyrenylphosphine, which becomes fluorescent when it is oxidized by hydroperoxides. The impact of antioxidant dispersions on emulsion kinetic stability was studied by UV–Vis turbidity measurements. The oxidation results were correlated to antioxidant extracts oxygen radical adsorption capacity (ORAC) and to emulsion kinetic stability. On the whole, antioxidants dispersions delayed the oxidation reaction to different extents in dependence on their ORAC values and their components amphiphilicity. Remarkably, among the antioxidants tested, the aqueous polyphenol extract from virgin olive oil was the most effective because it protected emulsions both from oxidation and from phase separation. Additionally, from this set of experiments, the primary role of the interfacial properties of olive oil polyphenols was highlighted.

Oligonucleotides and polynucleotides condensation onto liposome surface: effects of the base and of the nucleotide length.

The association behavior of different nucleic acids with cationic liposomes has been monitored, in order to find out how the polymer length, the type of base and the charge density affect the lipoplex formation. In particular the associative features displayed by the homopolymer 20-mer of adenine, Oligo (dA), of timine, Oligo (dT), and of guanine, Oligo (dG), were compared to understand the role of the base. The effects of the nucleic acid length and of the charge density were evaluated taking account of the association of the polyadenylic acid and of the DNA onto the liposomes. The results show that the homopolymer Oligo (dG) is able to interact with the cationic liposomes to the same extent as DNA, in spite of the fact that Oligo (dG) is a short polymer made of 20 residues and DNA is a longer and dual strand polymer having a higher charge density.

Biocompatible water-in-oil emulsion as a model to study ascorbic acid effect on lipid oxidation

A biocompatible water-in-oil (W/O) emulsion has been used as a model to study the effect of ascorbic acid (AA) on the oxidation of the oil (glycerol trioleate, GTO) continuous phase. The model system consisted of 3 wt % water dispersed in GTO containing 0.5 wt % sodium oleate (NaO)/oleic acid (OA) mixture (NaO/OA = 20/80 mol/mol %) as a stabilizer. To study the ascorbic acid effect on GTO light-promoted oxidation, we added aqueous solutions of ascorbic acid to GTO in place of distilled water. Results obtained as peroxide values show that ascorbic acid activity depends on its concentration and it is affected by the characteristics of the W/O interface. In the presence of ascorbyl palmitate (AP) or sorbitan trioleate (Span 85) in the continuous phase, ascorbic acid activity increases in the first few hours of oxidation. The effect of ascorbic acid has been related to emulsion structure by calculating characteristic parameters of the droplet size distributions by means of optical microscopy.

Ocular tissues and fluids oxidative stress in hares fed on verbascoside supplement

Abstract The influence of a prolonged diet supplemented with the powerful antioxidant verbascoside on the oxidative state of 20 healthy hares eye fluids and tissues has been studied. Verbascoside was dosed at 2, 3, 4 mg/die and the impact on the oxidative state of ocular tissues and fluids was tested by TBARS (thio barbituric acid reactive substances) and TEAC (trolox equivalent antioxidant capacity) assays. The percentage of change in antioxidant activity increased largely in retina and lenses at a daily verbascoside dose of 3 mg, whereas for optic nerve and vitreous humor the higher antioxidant capacity was measured at 4 mg/die verbascoside dose. The present findings demonstrate that verbascoside supplementation is able to protect ocular tissue and fluids from naturally occurring oxidation and that its protective effect depends on the daily dose, being maximum up to 3 mg/die.

Effects of verbascoside-based diet on blood and plasma constituents of rabbits

Objective: Oxidative stress brought on by free radicals can lead to an increased risk of some chronic pathologies. Antioxidants can scavenge free radicals by turning them into nonradical and nontoxic metabolites. The purpose of this study is to investigate the effect of a phenylpropanoid glycosides–based prolonged diet on blood constituents in animals. Methods: Tests were carried out on healthy New Zealand white rabbits and the following parameters were evaluated at baseline and after 90 days’ follow-up: plasma triglycerides, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, aspartate transaminase, alanine aminotransferase, bilirubin, the reactive oxygen metabolites, thiobarbituric acid–reactive substances, vitamin A, and vitamin E. The same parameters were analyzed in an age- and sex-matched animal control group. Results: We first defined the concept of average rate and then used it to calculate, by experimental data fitting, the formation or destruction rate of some blood or plasma constituents as a function of the daily dose. The results indicate that the effects can be categorized into 2 classes. The first includes the effects that produce monotonously continuous changes with daily dose, and the second includes those that exhibit a saturating trend. Conclusions: The experimental results suggest that high doses of verbascoside can potentially cause adverse effects through prooxidative effects. Risk is increased by the use of pharmacological doses of polyphenols in prevention, treatment, and as dietary supplements.

Adsorbent properties of olive mill wastes for chromate removal

ABSTRACT The removal of chromate ions from aqueous solutions by adsorption onto two differentolive mill waste materials was investigated using batch rate experiments. The solid materialwas obtained from olive mill wastes coming from two different extraction plants, two phasecontinuous, and discontinuous plant. The initial absence of chromium in the material wasconfirmed through scanning electron microscope equipped with Energy Dispersive X-rayanalyzer. The adsorption analysis has demonstrated that both biomasses are able to adsorbchromate ions. An accurate analysis of polyphenols has highlighted that the presence ofpolyphenols does not interfere with the adsorption of chromate ions. A heterogeneouskinetics model provided the parameters of the adsorption kinetics within all the time rangesexplored. For each biomass, a critical initial chromate concentration exists beyond which theadsorption process becomes independent of the initial chromate concentration. The resultsindicate that olive mill wastes may be reused as an adsorbent material for chromate ionsremoval by means of an ecologically friendly technology.Keywords: Biomass; Olive mill waste; Chromate; Adsorption

Thermal analysis of milling products and its implications in self-ignition

Thermal degradation of soft wheat, durum wheat, and maize as well as native starch and maize dextrin used to make fireworks, under nitrogen atmosphere, was studied by differential scanning calorimetry and thermogravimetric analysis. The results indicate that bran-free products give rise to a decomposition via transglycosylation-volatilization. On the contrary, wheat products containing bran or ligno-cellulosic residues decompose via exothermic reaction of dehydration-charring. For each product, the curve is determined as a function of its physical form, i.e., flour, ground product, and grain. The comparison of the conversion calculated as a first-order kinetics and the experimental, exhibits a very low mean square error. On this basis, the pyrolysis was assumed to obey first-order kinetics. The kinetic results were then used to estimate the temperature of spontaneous combustion, when these products are stored in silos. In particular, Frank-Kamenetskii theory is applied to prove how the products, under particular conditions, can become extremely explosive.

Corneal Epithelial Wound Healing Promoted by Verbascoside-Based Liposomal Eyedrops

Different liposomal formulations were prepared to identify those capable of forming eyedrops for corneal diseases. Liposomes with neutral or slightly positive surface charge interact very well with the cornea. Then these formulations were loaded with verbascoside to heal a burn of corneal epithelium induced by alkali. The cornea surface affected involved in wound was monitored as a function of time. Experimental results were modeled by balance equation between the rate of healing, due to the flow of phenylpropanoid, and growth of the wound. The results indicate a latency time of only three hours and furthermore the corneal epithelium heals in 48 hours. Thus, the topical administration of verbascoside appears to reduce the action time of cells, as verified by histochemical and immunofluorescence assays.