Antioxidant Activity of Metal Nanoparticles Coated with Tocopherol-Like Residues-The Importance of Studies in Homo- and Heterogeneous Systems

Antioxidant Activity of Bilirubin in Micellar and Liposomal Systems Is pH-Dependent

Bilirubin (BR), a product of heme catabolism, plays a critical role in biological systems. Although increased levels of BR result in hyperbilirubinemia or jaundice, there is increasing evidence that lower concentrations substantially decrease the risk of oxidative stress-mediated diseases due to antioxidant functions of BR. We studied the radical-trapping ability of BR in two model systems, micellar and liposomal, at a broad pH range. At pH < 6.0, BR behaves as a retardant; however, at pH ≥ 6.0, BR becomes strong radical trapping antioxidant, with rate constants for reaction with lipidperoxyl radicals (kinh) within the range from 1.2 × 104 M-1 s-1 to 3.5 × 104 M-1 s-1, and in liposomal system, the activity of BR is comparable to α-tocopherol. This transition is likely facilitated by the ionization of carboxyl groups, leading to a conformational shift in BR and improved solubility/localization at the water/lipid interface. This is the first experimental evidence of the role of pH on the antioxidant activity of bilirubin, and the observed pH-dependent radical-trapping ability of BR holds practical significance, particularly in jaundice treatment where light therapy targets the skin's weakly acidic surface. Minor adjustments toward neutral or alkaline pH can enhance radical-trapping action of BR, thereby mitigating oxidative stress induced with blue or violet light exposure.

Application of conventional metallic nanoparticles on male reproductive system - challenges and countermeasures

The application of nanotechnology in the present era has substantial impact on different industrial and medical fields. However, the advancement in nanotechnology for potential therapeutic and consumer benefits has been an anxious cause regarding the probable hazardous consequences of these molecules in biological systems and the environment. The toxic effects can perturb the physiologic system broadly and reproductive function and fertility specifically. Despite engineered nanomaterials (ENMs) having a wide range of applications, toxicological investigations of the probable ramifications of ENMs on the reproductive systems of mammals and fertility remains in its nascence. Complication in the male reproductive system is quite a pertinent issue in today's world which comprises of benign prostatic enlargement, prostate cancer, and unhealthy sperm production. The therapeutic drugs should not only be active in minimum dose but also site-specific in action, criteria being met by nanomedicines. Nanomedicine therapy is promising but encompasses the chances of adverse effects of being cytotoxic and generating oxidative stress. These hurdles can be overcome by creating coated nanoparticles with organic substances, modification of shape and size, and synthesizing biocompatible green nanoparticles. This review attempts to look into the applications of most widely used metals like zinc, titanium, silver, and gold nanoparticles in the therapy of the male reproductive system, their prospective harmful effects, and the way out to create a safe therapeutic system by specific modifications of these metal and metal oxide nanoparticles.

Advances in the control of lipid peroxidation in oil-in-water emulsions: kinetic approaches†

Large efforts have been, and still are, devoted to minimize the harmful effects of lipid peroxidation. Much of the early work focused in understanding both the lipid oxidation mechanisms and the action of antioxidants in bulk solution. However, food-grade oils are mostly present in the form of oil-in-water emulsions, bringing up an increasing complexity because of the three-dimensional interfacial region. This review presents an overview of the kinetic approaches employed in controlling the oxidative stability of edible oil-in-water emulsions and of the main outcomes, with particular emphasis on the role of antioxidants and on the kinetics of the inhibition reaction. Application of physical-organic chemistry methods, such as the pseudophase models to investigate antioxidant partitioning, constitute a remarkable example on how kinetic methodologies contribute to model chemical reactivity in multiphasic systems and to rationalize the role of interfaces, opening new opportunities for designing novel antioxidants with tailored properties and new prospects for modulating environmental conditions in attempting to optimize their efficiency. Here we will summarize the main kinetic features of the inhibition reaction and will discuss on the main factors affecting its rate, including the determination of antioxidant efficiencies from kinetic profiles, structure-reactivity relationships, partitioning of antioxidants and concentration effects.

Unexpected Role of pH and Microenvironment on the Antioxidant and Synergistic Activity of Resveratrol in Model Micellar and Liposomal Systems

Experimental and theoretical studies indicate that resveratrol (RSV, dietary polyphenol that effectively reduces cellular oxidative stress) is a good scavenger of hydroxyl, alkoxyl, and peroxyl radicals in homogeneous systems. However, the role of RSV as a chain-breaking antioxidant is still questioned. Here, we describe pH dependent effectiveness of RSV as an inhibitor of peroxidation of methyl linoleate in Triton X-100 micelles and in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes, with the best effectiveness at pH 6 (stoichiometric factors, n, are 4.9 and 5.6, and the rate constants for reaction with peroxyl radicals, k_inh, are 1200 and 3300 M^–1 s^–1 in micellar and liposomal systems, respectively). We propose the mechanism in which RSV-derived radicals are coupled to dimers with recovered ability to trap lipidperoxyl radicals. The formation of such dimers is facilitated due to increased local concentration of RSV at the lipid–water interface. Good synergy of RSV with α-tocopherol analogue in micelles and liposomes is in contrast to the previously reported lack of synergy in non-polar solvents; however, the increased persistency of tocopheroxyl radicals in dispersed lipid/water systems and proximal localization of both antioxidants greatly facilitate the possible recovery of α-TOH by RSV.

Novel Nanobiocomposites Based on Natural Polysaccharides as Universal Trophic Low-Dose Micronutrients

New promising manganese-containing nanobiocomposites (NCs) based on natural polysaccharides, arabinogalactan (AG), arabinogalactan sulfate (AGS), and κ-carrageenan (κ-CG) were studied to develop novel multi-purpose trophic low-dose organomineral fertilizers. The general toxicological effects of manganese (Mn) on the vegetation of potatoes (Solanum tuberosum L.) was evaluated in this study. The essential physicochemical properties of this trace element in plant tissues, such as its elemental analysis and its spectroscopic parameters in electron paramagnetic resonance (EPR), were determined. Potato plants grown in an NC-containing medium demonstrated better biometric parameters than in the control medium, and no Mn accumulated in plant tissues. In addition, the synthesized NCs demonstrated a pronounced antibacterial effect against the phytopathogenic bacterium Clavibacter sepedonicus (Cms) and were proved to be safe for natural soil microflora.

Self-Assembly and Multifaceted Bioactivity of a Silver(I) Quinolinate Coordination Polymer

Coordination polymers have emerged as a new class of potent biologically active agents due to a variety of important characteristics such as the presence of bioactive metal centers and linkers, low toxicity, stability, tailorable structures, and bioavailability. The research on intermediate metabolites has also been explored with implications toward the development of selective anticancer, antimicrobial, and antiviral therapeutic strategies. In particular, quinolinic acid (H2quin) is a recognized metabolite in kynurenine pathway and potent neurotoxic molecule, which has been selected in this study as a bioactive building block for assembling a new silver(I) coordination polymer, [Ag(Hquin)(μ-PTA)]n·H2O (1). This product has been prepared from silver oxide, H2quin, and 1,3,5-triaza-7-phosphaadamantane (PTA), and fully characterized by standard methods including single-crystal X-ray diffraction. Compound 1 has revealed distinctive bioactive features, namely (i) a remarkable antiviral activity against herpes simplex virus type 1 (HSV-1) and adenovirus 36 (Ad-36), (ii) a significant antibacterial activity against clinically important bacteria (Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa), and (iii) a selective cytotoxicity against HeLa (human cervix carcinoma) cell line. The present work widens a growing family of bioactive coordination polymers with potent antiviral, antibacterial, and antiproliferative activity.

Green Fabrication of Zinc Oxide Nanoparticles Using Phlomis Leaf Extract: Characterization and In Vitro Evaluation of Cytotoxicity and Antibacterial Properties

Green nanoparticle synthesis is an environmentally friendly approach that uses natural solvents. It is preferred over chemical and physical techniques due to the time and energy savings. This study aimed to synthesize zinc oxide nanoparticles (ZnO NPs) through a green method that used Phlomis leaf extract as an effective reducing agent. The synthesis and characterization of ZnO NPs were confirmed by UV-Vis spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Dynamic light scattering (DLS), Zeta potential, and Field Emission Scanning Electron Microscope (FESEM) techniques. In vitro cytotoxicity was determined in L929 normal fibroblast cells using MTT assay. The antibacterial activity of ZnO nanoparticles was investigated using a disk-diffusion method against S. aureus and E. coli, as well as minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) content concentrations. XRD results confirmed the nanoparticles’ crystalline structure. Nanoparticle sizes were found to be around 79 nm by FESEM, whereas the hydrodynamic radius of nanoparticles was estimated to be around 165 ± 3 nm by DLS. FTIR spectra revealed the formation of ZnO bonding and surfactant molecule adsorption on the surface of ZnO NPs. It is interesting to observe that aqueous extracts of Phlomis leave plant are efficient reducing agents for green synthesis of ZnO NPs in vitro, with no cytotoxic effect on L929 normal cells and a significant impact on the bacteria tested.

Methods to Determine Chain-Breaking Antioxidant Activity of Nanomaterials beyond DPPH•. A Review

This review highlights the progress made in recent years in understanding the mechanism of action of nanomaterials with antioxidant activity and in the chemical methods used to evaluate their activity. Nanomaterials represent one of the most recent frontiers in the research for improved antioxidants, but further development is hampered by a poor characterization of the ''antioxidant activity'' property and by using oversimplified chemical methods. Inhibited autoxidation experiments provide valuable information about the interaction with the most important radicals involved in the lipid oxidation, namely alkylperoxyl and hydroperoxyl radicals, and demonstrate unambiguously the ability to stop the oxidation of organic materials. It is proposed that autoxidation methods should always complement (and possibly replace) the use of assays based on the quenching of stable radicals (such as DPPH• and ABTS•+). The mechanisms leading to the inhibition of the autoxidation (sacrificial and catalytic radical trapping antioxidant activity) are described in the context of nanoantioxidants. Guidelines for the selection of the appropriate testing conditions and of meaningful kinetic analysis are also given.

Relationship between Antioxidant Activity and Ligand Basicity in the Dipicolinate Series of Oxovanadium(IV) and Dioxovanadium(V) Complexes

Oxidative stress plays an important role in the pathogenesis of many serious diseases, including cancer, atherosclerosis, coronary artery disease, Parkinson’s disease, Alzheimer’s disease, stroke and myocardial infarction. In the body’s natural biochemical processes, harmful free radicals are formed, which can be removed with the help of appropriate enzymes, a balanced diet or the supply of synthetic antioxidant substances such as flavonoids, vitamins or anthocyanins to the body. Due to the growing demand for antioxidant substances, new complex compounds of transition metal ions with potential antioxidant activity are constantly being sought. In this study, four oxovanadium(IV) and dioxovanadium(V) dipicolinate (dipic) complexes with 1,10-phenanthroline (phen), 2,2′-bipyridyl (bipy) and the protonated form of 2-phenylpyridine (2-phephyH): (1) [VO(dipic)(H₂O)₂]·2 H₂O, (2) [VO(dipic)(phen)]·3 H₂O, (3) [VO(dipic)(bipy)]·H₂O and (4) [VOO(dipic)](2-phepyH)·H₂O were synthesized including one new complex, so far unknown and not described in the literature, i.e., [VOO(dipic)](2-phepyH)·H₂O. The oxovanadium(IV) dipicolinate complexes with 1,10-phenanthroline and 2,2′-bipyridyl have been characterized by several physicochemical methods: NMR, MALDI-TOF-MS, IR, but new complex [VOO(dipic)](2-phepyH)·H₂O has been examined by XRD to confirm its structure. The antioxidant activities of four complexes have been examined by the nitrotetrazolium blue (NBT) method towards superoxide anion. All complexes exhibit high reactivity with superoxide anion and [VOO(dipic)](2-phepyH)·H₂O has higher antioxidant activity than L-ascorbic acid. Our studies confirmed that high basicity of the auxiliary ligand increases the reactivity of the complex with the superoxide radical.

Antioxidants: Classification, Natural Sources, Activity/Capacity Measurements, and Usefulness for the Synthesis of Nanoparticles

Natural extracts are the source of many antioxidant substances. They have proven useful not only as supplements preventing diseases caused by oxidative stress and food additives preventing oxidation but also as system components for the production of metallic nanoparticles by the so-called green synthesis. This is important given the drastically increased demand for nanomaterials in biomedical fields. The source of ecological technology for producing nanoparticles can be plants or microorganisms (yeast, algae, cyanobacteria, fungi, and bacteria). This review presents recently published research on the green synthesis of nanoparticles. The conditions of biosynthesis and possible mechanisms of nanoparticle formation with the participation of bacteria are presented. The potential of natural extracts for biogenic synthesis depends on the content of reducing substances. The assessment of the antioxidant activity of extracts as multicomponent mixtures is still a challenge for analytical chemistry. There is still no universal test for measuring total antioxidant capacity (TAC). There are many in vitro chemical tests that quantify the antioxidant scavenging activity of free radicals and their ability to chelate metals and that reduce free radical damage. This paper presents the classification of antioxidants and non-enzymatic methods of testing antioxidant capacity in vitro, with particular emphasis on methods based on nanoparticles. Examples of recent studies on the antioxidant activity of natural extracts obtained from different species such as plants, fungi, bacteria, algae, lichens, actinomycetes were collected, giving evaluation methods, reference antioxidants, and details on the preparation of extracts.

Vitamin E: A Review of Its Application and Methods of Detection When Combined with Implant Biomaterials

Vitamin E is a common compound used for tocopherols and tocotrienols (α, β, γ, δ); it is the component of many natural products of both plant and animal origin. Thanks to its powerful antioxidant capacity, vitamin E has been very successful in hip and knee arthroplasty, used to confer resistance to oxidation to irradiated UHMWPE. The positive results of these studies have made vitamin E an important object of research in the biomedical field, highlighting other important properties, such as anti-bacterial, -inflammatory, and -cancer activities. In fact, there is an extensive literature dealing with vitamin E in different kinds of material processing, drug delivery, and development of surface coatings. Vitamin E is widely discussed in the literature, and it is possible to find many reviews that discuss the biological role of vitamin E and its applications in food packaging and cosmetics. However, to date, there is not a review that discusses the biomedical applications of vitamin E and that points to the methods used to detect it within a solid. This review specifically aims to compile research about new biomedical applications of vitamin E carried out in the last 20 years, with the intention of providing an overview of the methodologies used to combine it with implantable biomaterials, as well as to detect and characterize it within these materials.

Interfacial kinetics in olive oil-in-water nanoemulsions: Relationships between rates of initiation of lipid peroxidation, induction times and effective interfacial antioxidant concentrations

HYPOTHESIS

A detailed quantitative description of the effects of antioxidants in inhibiting lipid peroxidation in oil-in-water emulsions can be achieved by determining the relationships between the rates of initiation of the lipid peroxidation reaction, the length of the induction period preceding the propagation step of the radical oxidation process and the effective antioxidant interfacial concentrations.

EXPERIMENTS

We successfully prepared and characterized a series of olive oil-in-water nanoemulsions and allowed them to spontaneously oxidize. Their oxidative stability was evaluated by carrying out in the presence, and absence, of antioxidants derived from gallic acid, by monitoring the formation of primary oxidation products with time, by determining the corresponding induction periods, and by determining the effective interfacial concentrations of the antioxidants in the intact emulsions.

FINDINGS

Results show that both, the length of the induction periods and the antioxidant interfacial concentrations change concomitantly, increasing with the hydrophobicity of the antioxidant up to a maximum at the octyl derivative; longer aliphatic chains decrease their efficiency. The ratio between the interfacial antioxidant concentration and the induction period remains constant independently of the antioxidant, demonstrating that the effective concentrations of antioxidant at the interface control their efficiencies in emulsions.

Effect of Antioxidants on High-Temperature Stability of Renewable Bio-Oils Revealed by an Innovative Method for the Determination of Kinetic Parameters of Oxidative Reactions

Bio-oils employed for various industrial purposes, such as biodiesel production, undergo extensive oxidation and degradation during transformation processes. Therefore, it is extremely important to predict their stability at high temperature. We report herein a new procedure based on the optically detected profile of headspace O₂ concentration during isotherms at 130 °C for evaluating the oxidation kinetic parameters of several bio-oil feedstocks. The slope of O₂ consumption and the induction period duration were related to the oil characteristics (molecular structure, acidity, and presence of intrinsic antioxidants or metals). The increase of the induction time caused by a standardized propyl gallate addition yielded a semiquantitative value of radical generation rate. Investigated oils included used cooking oils; mono-, di-, and triglycerides from natural sources; free fatty acids; transesterified oils; and their blends. With respect to other methods, this characterization presents the advantage of disentangling and evaluating the role of both fatty acids composition and naturally occurring antioxidants, and allows the development of rational strategies for antioxidant protection of oils and of their blends.

Formulation and evaluation of a topical liposomal gel containing a combination of zedoary turmeric oil and tretinoin for psoriasis activity

This study was to develop a combination of zedoary turmeric oil (ZTO) and tretinoin (TRE)-loaded liposomal gel as a topical drug delivery system. We used a combination of single-factor experiment and orthogonal experiment to systematically optimize encapsulation process of the compound liposomes. The optimized liposome vesicles were incorporated into Carbopol gel matrix and studied by continuous in vitro (skin penetration and retention) and in vivo (anti-psoriatic activity using mouse vaginal model and mouse tail model) experiments. The optimized liposomes had an entrapment efficiency (EE) of ZTO was (64.63 ± 1.00)%, EE of TRE was (90.33 ± 0.72)%, drug loading (DL) of ZTO was (9.09 ± 0.14)%, DL of TRE was (1.43 ± 0.02)%, particle size of 257.41 ± 7.58 nm, polydispersity index (PDI) of 0.10 ± 0.04 and zeta potential of -38.77 ± 0.81 mV. Transmission electron microscopy showed liposomes had a regular spherical surface. After 1-month storage at (4 ± 2)°C, the optimized liposome preparations maintained its stability. In vitro study indicated that liposome formulations could significantly prolong the penetration of drugs into the hair follicles of mice and keep more drugs in the skin compared with conventional gel formulations. In vivo study showed that liposomal gel was more effective than conventional gel in treating psoriasis and had a significant dose-dependent effect on psoriasis. In summary, liposomal gel is expected to be an ideal carrier for topical drug delivery systems of ZTO and TRE.

Hydroxycinnamyl Derived BODIPY as a Lipophilic Fluorescence Probe for Peroxyl Radicals

Herein, we describe the synthesis of a fluorescent probe NB-2 and its use for the detection of peroxyl radicals. This probe is composed of two receptor segments (4-hydroxycinnamyl moieties) sensitive towards peroxyl radicals that are conjugated with a fluorescent reporter, dipyrrometheneboron difluoride (BODIPY), whose emission changes depend on the oxidation state of the receptors. The measurement of the rate of peroxidation of methyl linoleate in a micellar system in the presence of 1.0 µM NB-2 confirmed its ability to trap lipid peroxyl radicals with the rate constant k_inh = 1000 M⁻¹·s⁻¹, which is ten-fold smaller than for pentamethylchromanol (an analog of α-tocopherol). The reaction of NB-2 with peroxyl radicals was further studied via fluorescence measurements in methanol, with α,α′-azobisisobutyronitrile (AIBN) used as a source of radicals generated by photolysis or thermolysis, and in the micellar system at pH 7.4, with 2,2′-azobis(2-amidinopropane) (ABAP) used as a thermal source of the radicals. The reaction of NB-2 receptors with peroxyl radicals manifests itself by the strong increase of a fluorescence with a maximum at 612–616 nm, with a 14-fold enhancement of emission in methanol and a 4-fold enhancement in the micelles, as compared to the unoxidized probe. Our preliminary results indicate that NB-2 behaves as a “switch on” fluorescent probe that is suitable for sensing peroxyl radicals in an organic lipid environment and in bi-phasic dispersed lipid systems.