This Review Article is focused on the action of the reactive oxygenated species in inducing oxidative injury of the lipid membrane components, as well as on the ability of antioxidants (of different ...structures and sources, and following different mechanisms of action) in fighting against oxidative stress.
Oxidative stress is defined as an excessive production of reactive oxygenated species that cannot be counteracted by the action of antioxidants, but also as a perturbation of cell redox balance. Reactive oxygenated/nitrogenated species are represented by superoxide anion radical, hydroxyl, alkoxyl and lipid peroxyl radicals, nitric oxide and peroxynitrite.
Oxidative stress determines structure modifications and function modulation in nucleic acids, lipids and proteins. Oxidative degradation of lipids yields malondialdehyde and 4-hydroxynonenal, but also isoprostanes, from unsaturated fatty acids. Protein damage may occur with thiol oxidation, carbonylation, side-chain oxidation, fragmentation, unfolding and misfolding, resulting activity loss. 8-hydroxydeoxyguanosine is an index of DNA damage.
The involvement of the reactive oxygenated/nitrogenated species in disease occurrence is described. The unbalance between the oxidant species and the antioxidant defense system may trigger specific factors responsible for oxidative damage in the cell: over-expression of oncogene genes, generation of mutagen compounds, promotion of atherogenic activity, senile plaque occurrence or inflammation. This leads to cancer, neurodegeneration, cardiovascular diseases, diabetes, kidney diseases.
The concept of antioxidant is defined, along with a discussion of the existent classification criteria: enzymatic and non-enzymatic, preventative or repair-systems, endogenous and exogenous, primary and secondary, hydrosoluble and liposoluble, natural or synthetic. Primary antioxidants are mainly chain breakers, able to scavenge radical species by hydrogen donation. Secondary antioxidants are singlet oxygen quenchers, peroxide decomposers, metal chelators, oxidative enzyme inhibitors or UV radiation absorbers.
The specific mechanism of action of the most important representatives of each antioxidant class (endogenous and exogenous) in preventing or inhibiting particular factors leading to oxidative injury in the cell, is then reviewed. Mutual influences, including synergistic effects are presented and discussed. Prooxidative influences likely to occur, as for instance in the presence of transition metal ions, are also reminded.
Display omitted
•Oxidative stress initiates structure and function alterations of key biomolecules.•The oxidant/antioxidant unbalance activates factors responsible for cell injury.•Reactive oxygenated/nitrogenated species become the source of disease occurrence.•General and specific antioxidant mechanisms prevent the oxidative damage.•Prooxidative effects may occur in some cases, like in the presence of transition metal ions.
The present review focuses on electrochemical methods for ascorbic acid assessment. The occurence, role, biological importance of vitamin C, as well as the non-electrochemical methods for its ...assessment are firstly reviewed. The electrochemical behavior of ascorbic acid is then illustrated, followed by a description of the potentiometric, voltammetric and amperometric methods for vitamin C content estimation in various media. Different methods for the development of electrochemical sensors are reviewed, from unmodified electrodes to different composites incorporating carbon nanotubes, ionic liquids or various mediators. From this perspective, the interaction between the functional groups of the sensor's material and the analyte molecule is discussed, as it is essential for the analytical characteristics obtained. The analytical performances of the potentiometric, voltammetric or amperometric chemical and biochemical sensors (linear range of analytical response, sensitivity, precision, stability, response time etc) are highlightened. The numerous applications of ascorbic acid electrochemical sensors in fields like food, pharmaceutical or clinical analysis, where vitamin C represents a key analyte, are also presented.
The present paper aims to review the natural food preservatives with antimicrobial properties emphasizing their importance for the future of food manufacturing and consumers' health. The extraction ...procedures applied to natural antimicrobials will be considered, followed by the description of some natural preservatives' antimicrobial mechanism of action, including (i) membrane rupture with ATP-ase activity inhibition, (ii) leakage of essential biomolecules from the cell, (iii) disruption of the proton motive force and (iiii) enzyme inactivation. Moreover, a provenance-based classification of natural antimicrobials is discussed by considering the sources of origin for the major natural preservative categories: plants, animals, microbes and fungi. As well, the structure influence on the antimicrobial potential is considered. Natural preservatives could also constitute a viable alternative to address the critical problem of microbial resistance, and to hamper the negative side effects of some synthetic compounds, while meeting the requirements for food safety, and exerting no negative impact on nutritional and sensory attributes of foodstuffs.
Display omitted
•Natural antimicrobials can derive from plants, animal sources, microorganisms, algae or mushrooms.•Natural antimicrobial agents may constitute a viable and safer alternative to synthetic ones.•Natural antimicrobials ensure food safety without impairing organoleptic or nutritional properties.•Action mechanism: rupture of microbial cell membrane, decay of proton motive force, interference with biomolecules’ activity.•The influence of structure proved crucial for the exhibited preservation potential of natural antimicrobials.
A method was developed for assessing ascorbic acid concentration in fruit juices and wine by differential pulse voltammetry. The oxidation peak for ascorbic acid occurs at about 530 mV (versus SCE) ...on a Pt strip working electrode and at about 470 mV on a carbon paste working electrode. The influence of the operational parameters like the pulse amplitude and the pulse period on the analytical signal was investigated. The obtained calibration graph shows a linear dependence between the peak height and ascorbic acid concentration within the range 0.31-20 mM with a Pt working electrode, and within the range 0.07-20 mM with a carbon paste working electrode. The equation of the calibration graph was y = 21.839x + 35.726, r² = 0.9940, when a Pt strip electrode was used (where y represents the value of the current intensity measured for the peak height, expressed as µA and x the analyte concentration, as mM). R.S.D. = 2.09%, n = 10, C(ascorbic acid) = 2.5 mM. The equation of the calibration graph was y = 3.4429x + 5.7334, r² = 0.9971, when a carbon paste electrode was used (where y represents the value of intensity measured for the peak height, expressed as µA and x the analyte concentration, as mM). R.S.D. = 2.35%, n = 10, C(ascorbic acid) = 2.5 mM. The developed method was applied to ascorbic acid assessment in fruit juices and wine. The ascorbic acid content determined ranged between 6.83 mg/100 mL juice for soft drinks (Fanta Madness) and 54.74 mg/100 mL for citrus (lemon) juices obtained by squeezing fruit. Different ascorbic acid concentrations (from standard solutions) were added to the analysed samples, the degree of recovery being comprised between 94.74 and 104.97%. The results of ascorbic acid assessment by differential pulse voltammetry were compared with those obtained by cyclic voltammetry. The results obtained by the two methods were in good agreement.
relies on the quorum sensing (QS) signaling system as a central regulator mechanism of virulence expression that contributes to the formation and maintenance of biofilms and tolerance to conventional ...antimicrobials. QS Signaling molecules (QSSMs) may be recognized and may function also within the host cells, being potentially involved in the progression of the infectious process. In this study we evaluate the expression of adhesion and inflammatory molecules in endothelial cells treated with
QSSMs, in order to bring new insights on the mechanisms involved in the interaction of
with host cells during the infectious process. Endothelial cells were stimulated with 20 µM of main
QSSMs (OdDHL =
-(3-oxododecanoyl)-L-homoserine lactone, C4HSL =
-butyryl-L-homoserine lactone, PQS = 2-heptyl-3-hydroxy-4(1
)-quinolone and HHQ = 2-heptyl-4-quinolone). Adherence to endothelial cells, inert substratum and biofilm formation was evaluated. The expression of adhesion molecules (VE-cadherin, PECAM-1, ICAM-1, and P-selectin) and inflammatory response molecules (IL-1β, IL-6, TNFα, TGFβ, and eNOS) was assessed by qRT-PCR and flow cytometry. Our results showed that bacterial adherence to inert substratum and biofilm were decreased in the presence of all tested QSSMs. The adherence index of PAO1 laboratory strain to host cells was decreased between 10-40% in the presence of QSSMs, as compared to untreated control. Expression of eukaryotic cells adhesion molecules ICAM-1 and P-selectin was stimulated by QSSMs, whereas VE-cadherin and PECAM-1 levels were increased only by C4HSL. The inflammatory response of endothelial cells was also modulated, as observed by the modified expression of IL-1β (for C4HSL, PQS and HHQ), IL-6 (for C4HSL and HHQ), TNFα (for C4HSL and HHQ), TGFβ, and eNOS factors. Our results demonstrate that the main pseudomonadal QSSMs differentially modulate endothelial cells adhesion and proinflammatory cytokine expression. These observations provide new insights in the mechanisms by which different QSSMs activate endothelial cells and modulate the infectious process, and support the importance of recent studies aiming to develop anti-QS therapeutic strategies to fight against
infections.
Sulfite is a widely applied preservation agent, against oxidative decay in foodstuffs and beverages. Among the analytical methods applied, electrochemical techniques exploit its facility to undergo ...oxidation. This paper aims at the comparative investigation of the performances exhibited by three analytical methodologies: cyclic voltammetry at different Pt working electrodes, the volumetric method employing sodium thiosulfate as titrating agent and the photocolorimetric method relying on the reduction of Fe
-orthophenanthroline complex by sulfite. The cyclic voltammetric assay was performed at Pt strip and Pt ring electrodes, by linearly sweeping the potential between -100 and 1,500 mV. The linear range corresponded to 7.5 mg L
– 4.0 g L
for Pt strip working electrode and to 15.5 mg L
– 4.0 g L
for Pt ring working electrode. Relative standard deviations smaller than 3% showed repeatability. RSD values smaller than 3% were also obtained in the photometric assay, but the latter was characterised by a narrower linear range. The Pt strip electrode allowed wider linear range and lower sensitivity, whereas the Pt ring electrode with Ag/AgCl reference in the same unit was characterised by better repeatability. Applications involved sulfite assay in vinegar, brown sugar and cider samples with consistency between cyclic voltammetry and titrimetry.
Antibiotic resistance is a major problem in current contemporary medicine and it has become a major concern of the 21st century. New resistance mechanisms developed by microorganisms spread greatly, ...threatening the ability to treat numerous infectious diseases, and increasing the number of nosocomial infections. Besides the role in immunology and glycobiology where they are used as hemaglutinine and identification of complex carbohydrates and glycoconjugates, lectins proved to mediate diversified biological functions like cytotoxicity, complement activation, cell-to-cell and host-pathogen communications, innate immune response, and cell-to-cell signalling. Recently, great interest has been developed for the research and applications of lectins in agriculture and medicine due to their antiparasitic and antimicrobial potentials. This review focuses on the recent data regarding the antimicrobial and antiparasitic activities of lectins, by presenting the role of lectins in host-pathogen interaction and also the cytotoxic effects on microorganisms and parasites. Identification and characterisation of new lectins with antimicrobial activity could serve as a natural alternative for the treatment of infections caused by antibiotic-resistant microorganisms and parasites.
Antioxidants are compounds that prevent or delay the oxidation process, acting at a much smaller concentration, in comparison to that of the preserved substrate. Primary antioxidants act as ...scavenging or chain breaking antioxidants, delaying initiation or interrupting propagation step. Secondary antioxidants quench singlet oxygen, decompose peroxides in non-radical species, chelate prooxidative metal ions, inhibit oxidative enzymes. Based on antioxidants’ reactivity, four lines of defense have been described: Preventative antioxidants, radical scavengers, repair antioxidants, and antioxidants relying on adaptation mechanisms. Carbon-based electrodes are largely employed in electroanalysis given their special features, that encompass large surface area, high electroconductivity, chemical stability, nanostructuring possibilities, facility of manufacturing at low cost, and easiness of surface modification. Largely employed methods encompass voltammetry, amperometry, biamperometry and potentiometry. Determination of key endogenous and exogenous individual antioxidants, as well as of antioxidant activity and its main contributors relied on unmodified or modified carbon electrodes, whose analytical parameters are detailed. Recent advances based on modifications with carbon-nanotubes or the use of hybrid nanocomposite materials are described. Large effective surface area, increased mass transport, electrocatalytical effects, improved sensitivity, and low detection limits in the nanomolar range were reported, with applications validated in complex media such as foodstuffs and biological samples.
The present review paper focuses on the chemistry of oxidative stress mitigation by antioxidants. Oxidative stress is understood as a lack of balance between the pro-oxidant and the antioxidant ...species. Reactive oxygen species in limited amounts are necessary for cell homeostasis and redox signaling. Excessive reactive oxygenated/nitrogenated species production, which counteracts the organism’s defense systems, is known as oxidative stress. Sustained attack of endogenous and exogenous ROS results in conformational and oxidative alterations in key biomolecules. Chronic oxidative stress is associated with oxidative modifications occurring in key biomolecules: lipid peroxidation, protein carbonylation, carbonyl (aldehyde/ketone) adduct formation, nitration, sulfoxidation, DNA impairment such strand breaks or nucleobase oxidation. Oxidative stress is tightly linked to the development of cancer, diabetes, neurodegeneration, cardiovascular diseases, rheumatoid arthritis, kidney disease, eye disease. The deleterious action of reactive oxygenated species and their role in the onset and progression of pathologies are discussed. The results of oxidative attack become themselves sources of oxidative stress, becoming part of a vicious cycle that amplifies oxidative impairment. The term antioxidant refers to a compound that is able to impede or retard oxidation, acting at a lower concentration compared to that of the protected substrate. Antioxidant intervention against the radicalic lipid peroxidation can involve different mechanisms. Chain breaking antioxidants are called primary antioxidants, acting by scavenging radical species, converting them into more stable radicals or non-radical species. Secondary antioxidants quench singlet oxygen, decompose peroxides, chelate prooxidative metal ions, inhibit oxidative enzymes. Moreover, four reactivity-based lines of defense have been identified: preventative antioxidants, radical scavengers, repair antioxidants, and those relying on adaptation mechanisms. The specific mechanism of a series of endogenous and exogenous antioxidants in particular aspects of oxidative stress, is detailed. The final section resumes critical conclusions regarding antioxidant supplementation.
Display omitted
•Pro-oxidant/antioxidant imbalance results in oxidative stress.•Oxidative stress implies deleterious alterations in biomolecules and disease occurrence.•The results of oxidative insults become themselves sources of oxidative stress.•Endogenous and exogenous antioxidants neutralize ROS and oxidative enzymes.•Supplements are recommended when oxidative stress surpasses the endogenous defense.
The present paper aims at reviewing and commenting on the analytical methods applied to antioxidant and antioxidant capacity assessment in plant-derived products. Aspects related to oxidative stress, ...reactive oxidative species’ influence on key biomolecules, and antioxidant benefits and modalities of action are discussed. Also, the oxidant-antioxidant balance is critically discussed. The conventional and nonconventional extraction procedures applied prior to analysis are also presented, as the extraction step is of pivotal importance for isolation and concentration of the compound(s) of interest before analysis. Then, the chromatographic, spectrometric, and electrochemical methods for antioxidant and antioxidant capacity determination in plant-derived products are detailed with respect to their principles, characteristics, and specific applications. Peculiarities related to the matrix characteristics and other factors influencing the method’s performances are discussed. Health benefits of plants and derived products are described, as indicated in the original source. Finally, critical and conclusive aspects are given when it comes to the choice of a particular extraction procedure and detection method, which should consider the nature of the sample, prevalent antioxidant/antioxidant class, and the mechanism underlying each technique. Advantages and disadvantages are discussed for each method.
PDF
