The potential pitfalls of using 1,1-diphenyl-2-picrylhydrazyl to characterize antioxidants in mixed water solvents

Improving the Antimicrobial Potency of Berberine for Endodontic Canal Irrigation Using Polymeric Nanoparticles

To address the challenges posed by biofilm presence and achieve a substantial reduction in bacterial load within root canals during endodontic treatment, various irrigants, including nanoparticle suspensions, have been recommended. Berberine (BBR), a natural alkaloid derived from various plants, has demonstrated potential applications in dentistry treatments due to its prominent antimicrobial, anti-inflammatory, and antioxidant properties. This study aimed to produce and characterize a novel polymeric nanoparticle of poly (lactic-co-glycolic acid) (PLGA) loaded with berberine and evaluate its antimicrobial activity against relevant endodontic pathogens, Enterococcus faecalis, and Candida albicans. Additionally, its cytocompatibility using gingival fibroblasts was assessed. The polymeric nanoparticle was prepared by the nanoprecipitation method. Physicochemical characterization revealed spheric nanoparticles around 140 nm with ca, -6 mV of surface charge, which was unaffected by the presence of BBR. The alkaloid was successfully incorporated at an encapsulation efficiency of 77% and the designed nanoparticles were stable upon 20 weeks of storage at 4 °C and 25 °C. Free BBR reduced planktonic growth at ≥125 μg/mL. Upon incorporation into PLGA nanoparticles, 20 μg/mL of [BBR]-loaded nanoparticles lead to a significant reduction, after 1 h of contact, of both planktonic bacteria and yeast. Sessile cells within biofilms were also considered. At 30 and 40 μg/mL, [BBR]-loaded PLGA nanoparticles reduced the viability of the sessile endodontic bacteria, upon 24 h of exposure. The cytotoxicity of BBR-loaded nanoparticles to oral fibroblasts was negligible. The novel berberine-loaded polymeric nanoparticles hold potential as a promising supplementary approach in the treatment of endodontic infections.

Squid meal and shrimp hydrolysate as novel protein sources for dog food

The world's growing pet population is raising sustainability and environmental concerns for the petfood industry. Protein-rich marine by-products might contribute to mitigating negative environmental effects, decreasing waste, and improving economic efficiency. The present study evaluated two marine by-products, squid meal and shrimp hydrolysate, as novel protein sources for dog feeding. Along with the analysis of chemical composition and antioxidant activity, palatability was evaluated by comparing a commercial diet (basal diet) and diets with the inclusion of 150 g kg-1 of squid meal or shrimp hydrolysate using 12 Beagle dogs (2.2 ± 0.03 years). Two in vivo digestibility trials were conducted with six dogs, three experimental periods (10 days each) and three dietary inclusion levels (50, 100 and 150 g kg-1) of squid meal or shrimp hydrolysate in place of the basal diet to evaluate effects of inclusion level on apparent total tract digestibility (ATTD), metabolizable energy content, fecal characteristics, metabolites, and microbiota. Both protein sources presented higher protein and methionine contents than ingredients traditionally used in dog food formulation. Shrimp hydrolysate showed higher antioxidant activity than squid meal. First approach and taste were not affected by the inclusion of protein sources, but animals showed a preference for the basal diet. Effects on nutrient intake reflected the chemical composition of diets, and fecal output and characteristics were not affected by the increasing inclusion levels of both protein sources. The higher ATTD of dry matter, most nutrients and energy of diets with the inclusion of both by-products when compared to the basal diet, suggests their potential to be included in highly digestible diets for dogs. Although not affected by the inclusion level of protein sources, when compared to the basal diet, the inclusion of squid meal decreased butyrate concentration and shrimp hydrolysate increased all volatile fatty acids, except butyrate. Fecal microbiota was not affected by squid meal inclusion, whereas inclusion levels of shrimp hydrolysate significantly affected abundances of Oscillosperaceae (UCG-005), Firmicutes and Lactobacillus. Overall, results suggest that squid meal and shrimp hydrolysate constitute novel and promising protein sources for dog food, but further research is needed to fully evaluate their functional value.

Antioxidant peptides, the guardian of life from oxidative stress

Reactive oxygen species (ROS) are produced during oxidative metabolism in aerobic organisms. Under normal conditions, ROS production and elimination are in a relatively balanced state. However, under internal or external environmental stress, such as high glucose levels or UV radiation, ROS production can increase significantly, leading to oxidative stress. Excess ROS production not only damages biomolecules but is also closely associated with the pathogenesis of many diseases, such as skin photoaging, diabetes, and cancer. Antioxidant peptides (AOPs) are naturally occurring or artificially designed peptides that can reduce the levels of ROS and other pro-oxidants, thus showing great potential in the treatment of oxidative stress-related diseases. In this review, we discussed ROS production and its role in inducing oxidative stress-related diseases in humans. Additionally, we discussed the sources, mechanism of action, and evaluation methods of AOPs and provided directions for future studies on AOPs.

Antioxidant and Antidiabetic Properties of Phlorotannins from Ascophyllum nodosum Seaweed Extracts

Seaweeds have gained considerable attention in recent years due to their potential health benefits and high contents of bioactive compounds. This review focuses on the exploration of seaweed's health-promoting properties, with particular emphasis on phlorotannins, a class of bioactive compounds known for their antioxidant and antidiabetic properties. Various novel and ecofriendly extraction methods, including solid-liquid extraction, ultrasound-assisted extraction, and microwave-assisted extraction are examined for their effectiveness in isolating phlorotannins. The chemical structure and isolation of phlorotannins are discussed, along with methods for their characterization, such as spectrophotometry, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and chromatography. Special attention is given to the antioxidant activity of phlorotannins. The inhibitory capacities of polyphenols, specifically phlorotannins from Ascophyllum nodosum against digestive enzymes, such as α-amylase and α-glucosidase, are explored. The results suggest that polyphenols from Ascophyllum nodosum seaweed hold significant potential as enzyme inhibitors, although the inhibitory activity may vary depending on the extraction conditions and the specific enzyme involved. In conclusion, seaweed exhibits great potential as a functional food ingredient for promoting health and preventing chronic diseases. Overall, this review aims to condense a comprehensive collection of high-yield, low-cost, and ecofriendly extraction methods for obtaining phlorotannins with remarkable antioxidant and antidiabetic capacities.

Spectrophotometric Methods for Measurement of Antioxidant Activity in Food and Pharmaceuticals

In recent years, there has been a growing interest in the application of antioxidants in food and pharmaceuticals due to their association with beneficial health effects against numerous oxidative-related human diseases. The antioxidant potential can be measured by various assays with specific mechanisms of action, including hydrogen atom transfer, single electron transfer, and targeted scavenging activities. Understanding the chemistry of mechanisms, advantages, and limitations of the methods is critical for the proper selection of techniques for the valid assessment of antioxidant activity in specific samples or conditions. There are various analytical techniques available for determining the antioxidant activity of biological samples, including food and plant extracts. The different methods are categorized into three main groups, such as spectrometry, chromatography, and electrochemistry techniques. Among these assays, spectrophotometric methods are considered the most common analytical technique for the determination of the antioxidant potential due to their sensitivity, rapidness, low cost, and reproducibility. This review covers the mechanism of actions and color changes that occur in each method. Furthermore, the advantages and limitations of spectrophotometric methods are described and discussed in this review.

Extraction and characterization of phenolic compounds and their potential antioxidant activities

For thousands of years, plant has been widely applied in the medical area and is an important part of human diet. A high content of nutrients could be found in all kinds of plants, and the most outstanding group of nutrients that attracts scientists' attention is the high level of phenolic compounds. Due to the relationship between high phenolic compound content and high antioxidant capacity, plant extracts are expected to become a potential treatment for oxidation stress diseases including diabetes and cancer. However, according to the instability of phenolic compounds to light and oxygen, there are certain difficulties in the extraction of such compounds. But after many years of development, the extraction technology of phenolic compounds has been quite stable, and the only problem is how to obtain high-quality extracts with high efficiency. To further enhance the value of plant extracts, concentration and separation methods are often applied, and when detailed analysis is required, characterization methods including HPLC and LC/GC-MS will be applied to evaluate the number and type of phenolic compounds. A series of antioxidant assays are widely performed in numerous studies to test the antioxidant capacity of the plant extracts, which is also an important basis for evaluating value of extracts. This paper intends to provide a view of a variety of methods used in plants' phenolic compound extraction, separation, and characterization. Furthermore, this review presents the advantages and disadvantages of techniques involved in phenolic compound research and provides selected representative bibliographic examples.

Evaluation of The Antioxidant Capacity of Food Products: Methods, Applications and Limitations

Assays of total antioxidant capacity (TAC) are popular in the analysis of food products. This review presents the most popular assays of TAC and their limitations, databases of TAC of food products, their application in clinical studies, and the effect of processing on the TAC of food. The importance of sample preparation for TAC assays and striking effects of digestion in the gastrointestinal tract on the TAC of food are discussed. Critical opinions on the validity of food TAC assays are considered. It is concluded that TAC methods can be useful as screening assays for food quality control and as low-cost, high-throughput tools used to discover potential antioxidant sources and follow changes in the content of antioxidants during food processing. However, effects revealed by TAC assays should be followed and explained using more specific methods.

The Novel Potentiometric Approach to Antioxidant Capacity Assay Based on the Reaction with Stable Radical 2,2'-diphenyl-1-picrylhydrazyl

For the first time, new possibilities of using the DPPH^• as a signal-forming oxidant molecule with potentiometric detection are shown. The CV method confirmed the presence of a quasi-reversible potential-determining system DPPH^•/DPPH-H under experimental conditions. This fact makes it possible to use DPPH^• as the model of the oxidizing agent for obtaining an analytical signal by the potentiometry method. The potentiometric approach makes it possible to obtain the value of the Nernst slope and the antioxidant capacity in one experiment. It consists of an antioxidant supplement and two consecutive DPPH^• supplements. In this case, the calculation of the Nernst slope is carried out by introducing the second addition of the oxidizing agent and constructing a calibration curve against the reaction background with an antioxidant. Solutions of individual antioxidants α-tocopherol, quercetin, (±)-catechin hydrate, and α-lipoic acid were studied by the developed approach. A high correlation with the results of spectrophotometric measurements is shown. At the same time, the potentiometry method is devoid of the concentration limitations of the spectrophotometric method, which was confirmed. In the study of plant materials extracts, a high correlation of antioxidant capacity, obtained by potentiometric and spectrophotometric methods, was shown only for objects whose color did not contribute to the DPPH^• absorption. The versatility of the potentiometric method for studying objects of any color was shown.

Effect of Extraction Method on the Bioactive Composition, Antimicrobial Activity and Phytotoxicity of Pomegranate By-Products

Pomegranate by-products can be an asset to the food industry due to the richness in bioactive and antimicrobial compounds. This work studied the influence of conventional solvent and sonication-assisted extraction methods on the bioactive profile, antimicrobial properties, and phytotoxicity effect of the peels and seeds extracts from Acco, Big Full, and Wonderful pomegranate cultivars. The bioactive composition of the extracts was evaluated for the content of total phenolics, total flavonoids, and antioxidant activity (expressed as the half-maximal inhibitory concentration—IC₅₀) by spectrophotometric methods, while the tannins were determined by titration and the anthocyanins were estimated by the pH-differential method. For the evaluation of the antimicrobial activity, the disk diffusion method of Kirby-Bauer was adapted through inhibition halos against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus, and Yarrowia lipolytica. The extracts’ phytotoxicity was evaluated in vitro on garden-cress seeds. Extracts from conventional extraction were richer in total phenolics, expressed as gallic acid equivalents (0.16–0.73 mg GAE/mg extract), while those from sonication-assisted extraction had higher contents of total flavonoids, expressed as catechin equivalents (0.019–0.068 mg CATE/mg extract); anthocyanins, expressed as cyanidin-3-glucoside (0.06–0.60 µg C3G/mg, dry basis); and antioxidant activity (IC₅₀, 0.01–0.20 mg/mL). All extracts were more effective against Gram-positive bacteria and yeasts than Gram-negative bacteria. In general, the sonication-assisted extracts led to higher inhibition halos (8.7 to 11.4 mm). All extracts presented phytotoxicity against garden-cress seeds in the tested concentrations. Only the lowest concentration (0.003 mg/mL) enabled the germination of seeds and root growth, and the sonication-assisted extracts showed the highest Munoo-Liisa vitality index (51.3%). Overall, sonication-assisted extraction obtained extracts with greater bioactive and antimicrobial potential and less phytotoxicity.

Concentration-dependent HAT/ET mechanism of the reaction of phenols with 2,2-diphenyl-1-picrylhydrazyl (dpph˙) in methanol

The reaction of a 2,2-diphenyl-1-picrylhydrazyl radical (dpph˙) with phenols carried out in alcohols is a frequently used assay for estimation of the antiradical activity of phenolic compounds. The rates of reactions of dpph˙ with five phenols (ArOH: unsubstituted phenol, 4-hydroxyacetophenone, two calix[4]resorcinarenes and baicalein) measured in methanol indicate the different kinetics of the process for very diluted phenols compared to their non-diluted solutions. This effect was explained as dependent on the ratio [ArO⁻]/[ArOH] and for diluted ArOH corresponds to an increased contribution of much faster electron transfer (ET, ArO⁻/dpph˙) over the Hydrogen Atom Transfer (HAT, ArOH/dpph˙). Simplified analysis of the reaction kinetics resulted in estimation of k^ET/k^HAT ratios for each studied ArOH, and in calculation of the rate constants k^ET. Described results are cautionary examples of how the concentration of a phenol might change the reaction mechanism and the overall kinetics of the observed process.

Concentration dependent contribution of hydrogen atom transfer and electron transfer to the overall kinetics of reaction of phenols with a 2,2-diphenyl-1-picrylhydrazyl radical in methanol.

The Potential of Dietary Antioxidants from a Series of Plant Extracts as Anticancer Agents against Melanoma, Glioblastoma, and Breast Cancer

In modern society, cancer is one of the most relevant medical problems. It is important to search for promising plant raw materials whose extracts have strong antioxidant and anticancer effects. The aim of this study was to determine the composition of phenolic compounds in plant extracts, to evaluate their antioxidant and anticancer activity, and to find the correlations between those activities. Extracts of calendula, sage, bearberry, eucalyptus, yarrow, and apple were selected for the study. The phenolic compounds of these extracts were determined by the UPLC-ESI-MS/MS method and the antioxidant activity was evaluated in vitro by four different UV-VIS spectrophotometric methods (ABTS, DPPH, CUPRAC, FRAP). The anticancer activity of extracts was tested against melanoma IGR39, glioblastoma U-87, and triple-negative breast cancer MDA-MB-231 cell lines in vitro by MTT assay. The highest content of identified and quantified phenolic compounds was found in sage leaf extract and the lowest in ethanol eucalyptus leaf extract. The highest antioxidant activity was determined by all applied methods for the acetone eucalyptus leaf extract. The majority of extracts were mostly active against the melanoma IGR39 cell line, and possessed the lowest activity against the glioblastoma U-87 cell line. Acetone extract of eucalyptus leaf samples exhibited the highest anticancer activity against all tested cell lines. Strong and reliable correlation has been found between antioxidant and anticancer activity in breast cancer and glioblastoma cell lines, especially when evaluating antioxidant activity by the FRAP method.

Formulation of Ocular In Situ Gels with Lithuanian Royal Jelly and Their Biopharmaceutical Evaluation In Vitro

Royal jelly is a natural substance produced by worker bees that possesses a variety of biological activities, including antioxidant, anti-inflammatory, antibacterial, and protective. Although fresh royal jelly is kept at low temperatures, to increase its stability, it needs to be incorporated into pharmaceutical formulations, such as in situ gels. The aim of this study was to formulate in situ ocular gels containing Lithuanian royal jelly for topical corneal use in order to increase the retention time of the formulation on the ocular surface and bioavailability. Gels were evaluated for physicochemical characteristics (pH, rheological properties, refractive index) and in vitro drug release measuring the amount of 10-hydroxy-2-decenoic acid (10-HDA). An ocular irritation test and cell viability tests were performed using the SIRC (Statens Seruminstitut Rabbit Cornea) cell culture line. Results indicated that all the in situ gels were within an acceptable pH and refractive index range close to corneal properties. Rheology studies have shown that the gelation temperature varies between 25 and 32 °C, depending on the amount of poloxamers. The release studies have shown that the release of 10-HDA from in situ gels is more sustained than royal jelly suspension. All gel formulations were non-irritant according to the short-time exposure test (STE) using the SIRC cell culture line, and long-term cell viability studies indicated that the formulations used in small concentrations did not induce cell death. Prepared in situ gels containing royal jelly have potential for ocular drug delivery, and they may improve the bioavailability, stability of royal jelly, and formation of non-irritant ocular formulations.

Analytical Methods Used in Determining Antioxidant Activity: A Review

The study of antioxidants and their implications in various fields, from food engineering to medicine and pharmacy, is of major interest to the scientific community. The present paper is a critical presentation of the most important tests used to determine the antioxidant activity, detection mechanism, applicability, advantages and disadvantages of these methods. Out of the tests based on the transfer of a hydrogen atom, the following were presented: the Oxygen Radical Absorption Capacity (ORAC) test, the Hydroxyl Radical Antioxidant Capacity (HORAC) test, the Total Peroxyl Radical Trapping Antioxidant Parameter (TRAP) test, and the Total Oxyradical Scavenging Capacity (TOSC) test. The tests based on the transfer of one electron include the Cupric Reducing Antioxidant Power (CUPRAC) test, the Ferric Reducing Antioxidant Power (FRAP) test, the Folin-Ciocalteu test. Mixed tests, including the transfer of both a hydrogen atom and an electron, include the 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) test, and the [2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl] (DPPH) test. All these assays are based on chemical reactions and assessing the kinetics or reaching the equilibrium state relies on spectrophotometry, presupposing the occurrence of characteristic colours or the discolouration of the solutions to be analysed, which are processes monitored by specific wavelength adsorption. These assays were successfully applied in antioxidant analysis or the determination of the antioxidant capacity of complex samples. As a complementary method in such studies, one may use methods based on electrochemical (bio)sensors, requiring stages of calibration and validation. The use of chemical methods together with electrochemical methods may result in clarification of the operating mechanisms and kinetics of the processes involving several antioxidants.

Antioxidants and antioxidant methods: an updated overview

Antioxidants had a growing interest owing to their protective roles in food and pharmaceutical products against oxidative deterioration and in the body and against oxidative stress-mediated pathological processes. Screening of antioxidant properties of plants and plant-derived compounds requires appropriate methods, which address the mechanism of antioxidant activity and focus on the kinetics of the reactions including the antioxidants. Many studies evaluating the antioxidant activity of various samples of research interest using different methods in food and human health have been conducted. These methods are classified, described, and discussed in this review. Methods based on inhibited autoxidation are the most suited for termination-enhancing antioxidants and for chain-breaking antioxidants, while different specific studies are needed for preventive antioxidants. For this purpose, the most common methods used in vitro determination of antioxidant capacity of food constituents were examined. Also, a selection of chemical testing methods was critically reviewed and highlighted. In addition, their advantages, disadvantages, limitations and usefulness were discussed and investigated for pure molecules and raw extracts. The effect and influence of the reaction medium on the performance of antioxidants are also addressed. Hence, this overview provides a basis and rationale for developing standardized antioxidant methods for the food, nutraceuticals, and dietary supplement industries. In addition, the most important advantages and shortcomings of each method were detected and highlighted. The chemical principles of these methods are outlined and critically discussed. The chemical principles of methods of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical (ABTS^·+) scavenging, 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radical scavenging, Fe³⁺-Fe²⁺ transformation assay, ferric reducing antioxidant power (FRAP) assay, cupric ions (Cu²⁺) reducing power assay (Cuprac), Folin-Ciocalteu reducing capacity (FCR assay), peroxyl radical (ROO·), superoxide radical anion (O₂^·-), hydrogen peroxide (H₂O₂) scavenging assay, hydroxyl radical (OH·) scavenging assay, singlet oxygen (¹O₂) quenching assay, nitric oxide radical (NO·) scavenging assay and chemiluminescence assay are outlined and critically discussed. Also, the general antioxidant aspects of main food components were discussed by a number of methods, which are currently used for the detection of antioxidant properties of food components. This review consists of two main sections. The first section is devoted to the main components in the food and pharmaceutical applications. The second general section comprises some definitions of the main antioxidant methods commonly used for the determination of the antioxidant activity of components. In addition, some chemical, mechanistic and kinetic basis, and technical details of the used methods are given.

Ultrasound-Assisted Extraction for the Recovery of Carotenoids from Guava's Pulp and Waste Powders

In this work, lycopene- and β-carotene-rich extracts were obtained from guava's pulp and waste powders using maceration (ME), ultrasonic bath (BUAE, 25 °C for 30 min), and ultrasonic probe (PUAE, 25 °C for 5 min). Extracts were evaluated for total carotenoid content, antioxidant capacity, color, and lycopene and β-carotene content by HPLC-DAD. Bath-type ultrasound-assisted extraction (BUAE) was the best technique to obtain lycopene from guava pulp (135.0 mg 100 g^-1) and waste (76.64 mg 100 g^-1), followed by ME (pulp = 107.6, waste = 43.57 mg 100 g^-1), and PUAE (pulp = 44.19, waste = 33.83 mg 100 g^-1). The total carotenoid content positively affected the extracts' antioxidant capacity. Dehydration of guava fractions showed to be an efficient method to increase carotenoid availability. This is the first work to report the recovery of carotenoids from guava by ultrasonic extraction. Furthermore, this method has shown to be a suitable approach to reduce extraction time and solvent use. These extracts could be further applied to lipid-rich foods as a natural antioxidant and/or as an ingredient in the development of functional foods.

Thermodynamics of primary antioxidant action of flavonols in polar solvents

Very recently, a report on the antioxidant activity of flavonoids has appeared, where authors concluded that Hydrogen Atom Transfer mechanism represents the thermodynamically preferred mechanism in polar media (https://doi.org/10.1016/j.foodres.2018.11.018). Unfortunately, serious errors in the theoretical part of the paper led to incorrect conclusions. For six flavonols (galangin, kaempferol, quercetin, morin, myricetin, and fisetin), reaction enthalpies related to three mechanisms of the primary antioxidant action were computed. Based on the obtained results, the role of intramolecular hydrogen bonds (IHB) in the thermodynamics of the antioxidant effect is presented. Calculations and the role of solvation enthalpies of proton and electron in the determination of thermodynamically preferred mechanism is also briefly explained and discussed. The obtained results are in accordance with published works considering the Sequential Proton-Loss Electron-Transfer thermodynamically preferred reaction pathway.

Synthesis and encapsulation of V(IV,V) compounds in silica nanoparticles targeting development of antioxidant and antiradical nanomaterials

The quest for effective treatments of oxidative stress has concentrated over the years on new nanomaterials with improved antioxidant and antiradical activity, thereby attracting broad research interest. In that regard, research efforts in our lab were launched to pursue such hybrid materials involving a) synthesis of silica gel matrices, b) evaluation of the suitability of atoxic matrices as potential carriers for the controlled release of V(IV)(VOSO₄), V(V)(NaVO₃) compounds and a newly synthesized heterometallic lithium-vanadium(IV,V) tetranuclear compound containing vanadium-bound hydroxycarboxylic 1,3-diamine-2-propanol-N,N,N',N'-tetraacetic acid (DPOT), and c) investigation of structural and textural properties of silica nanoparticles (NPs) by different and complementary characterization techniques, inquiring into the nature of the encapsulated vanadium species and their interaction with the siloxane matrix, collectively targeting novel antioxidant and antiradical nanomaterials biotechnology. The physicochemical characterization of the vanadium-loaded SiO₂ NPs led to the formulation of optimized material configuration linked to the delivery of the encapsulated antioxidant-antiradical load. Entrapment and drug release studies showed a) the competence of hybrid nanoparticles with respect to encapsulation efficiency of the vanadium compound (concentration dependence), b) congruence with the physicochemical features determined, and c) a well-defined release profile of NP load. Antioxidant properties and the free radical scavenging capacity of the new hybrid materials (containing VOSO₄, NaVO₃, and V-DPOT) were demonstrated through a) 2-diphenyl-1-picrylhydrazyl (DPPH) free radical, and b) intracellular-extracellular reactive oxygen species (ROS) assays, through UV-Visible spectroscopy techniques, collectively showing that the hybrid silica NPs (empty-loaded) could serve as an efficient platform for nanodrug formulations counteracting oxidative stress.

Antioxidant activity, neuroprotective properties and bioactive constituents analysis of varying polarity extracts from Eucalyptus globulus leaves

Eucalyptus globulus is employed as herbal tea and therapeutical purposes. In this work, it is investigated for first time the neuroprotective activities, based on antioxidant properties, of varying polarity extracts (acetone, ethanol and methanol) from E. globulus leaves and elucidate their main bioactive constituents. Methanol and acetone extracts contained the highest phenolic compounds amount and chlorogenic acid was the major compound identified by UPLC-ESI-MS/MS. Moreover, the three tested extracts showed significant antioxidant properties, varying their potency depending on the in vitro technique used. Furthermore, E. globulus extracts were effective in ameliorating H₂O₂-induced oxidative stress by increasing cell viability, GSH levels and antioxidant enzymes activity and, by decreasing ROS production and lipid peroxidation levels in SH-SY5Y cells. Taken together, E. globulus leaves extracts could be used as raw material for food and pharmaceutical supplements for their high content in antioxidant compounds with health benefits properties against oxidative stress.

Preparation and characterization of quercetin/dietary fiber nanoformulations

Quercetin is well known for its beneficial health effects on the human body. However, the slow dissolution rate leading to poor bioavailability constitutes a barrier to being further developed for nutritional products. In this work, quercetin was co-precipitated with dietary fibers into a fast-dissolving nanoformulation via antisolvent precipitation, followed by spray drying. With the help of cellulose fiber, resistant starch or resistant maltodextrin, a high dissolution rate and good storage stability was achieved for quercetin nanoformulations. In addition, nanoformulations exhibited higher level of antioxidant activities in contrast to raw quercetin. The developed quercetin/dietary fiber nanoformulations could be used as supplements or functional ingredients for food development.

Pitfalls of using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay to assess the radical scavenging activity of peptides: Its susceptibility to interference and low reactivity towards peptides

DPPH assay is widely used to evaluate the radical scavenging activities of peptides. Effects of pH and buffers on the stability of DPPH• and its reduced product (DPPHH) in the ethanol-buffer solution were investigated in this study and the reactivity of DPPH• towards several dipeptides was compared to that of 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•⁺) and the peroxyl radicals in oxygen radical absorbance capacity (ORAC) assay. Results showed that the deprotonation of DPPHH under basic condition could interfere with the spectrophotometric measurement at 515-525nm. It was suggested that the reaction mixture be maintained at a final pH range of 5.0-6.5 in 1:1 ethanol-acetate/citrate buffer medium when evaluating the activities of peptides. Additionally, among tested dipeptides, only Cys-containing dipeptides displayed DPPH• scavenging activity with 0.14-0.28μmol TE (Trolox equivalent)/μmol, while Tyr/Trp-containing dipeptides with high reactivity towards ABTS•⁺ and peroxyl radicals were inert to DPPH• with TE values less than 0.02.

Antioxidant activity of dopamine and L-DOPA in lipid micelles and their cooperation with an analogue of α-tocopherol

Oxidative stress contributes to the progression of neurodegenerative diseases and considerable attention has been given to the development of new antioxidant-based therapies aimed at limiting neuronal cell damage. Structural analysis of catecholamine neurotransmitters indicates that these molecules can exhibit antioxidant activity due to the presence of a catechol moiety. This hypothesis is confirmed in cell culture experiments but the mechanism of antioxidant action of catecholamines is not described. Herein, we present quantitative kinetic studies on the effect of dopamine (DA) and L-3,4-dihydroxyphenylalanine (L-DOPA) on the peroxidation of methyl linoleate dispersed in Triton X-100 micelles as a model heterogeneous lipid system. Experiments were performed at extended pH range 4.0-10.0 in order to study how protonation/deprotonation of catecholamine affect its antioxidant activity. At pH 4.0-7.0, the activity of catecholamines is limited to retardation of lipid peroxidation (caused by the reaction of catecholamines with initiating radicals in the aqueous phase). The effective suppression of lipid peroxidation can be achieved by applying catecholamines together with an analogue of α-tocopherol (2,2,5,7,8-pentamethyl-6-hydroxychroman, PMHC). For example, a mixture of 1 μM PMHC with 10 μM L-DOPA causes 18-fold elongation of suppression time as compared to 1 μM PMHC used alone. We suggest that catecholamines together with α-tocopherol efficiently enhance the protection of biological systems from oxidative stress. At pH above 8.0 a prooxidative effect caused by reaction of semiquinone radical anions with molecular oxygen is observed. However, this toxic action can be completely suppressed by PMHC acting as an agent removing the potentially harmful semiquinone radicals from the reaction environment.

An enolato-bridged dinuclear Cu(ii) complex with a coumarin-assisted precursor: a spectral, magnetic and biological study

Coumarin assisted dinuclear [Cu₂(L)₂(DMF)₂] (1) shows weak ferromagnetic interaction and a geometric distortion occurs while lowering the temperature in EPR.

In Vitro Protocols for Measuring the Antioxidant Capacity of Algal Extracts

In the last decade a large amount of research has been directed at targeting algal resources for biologically active molecules. High-throughput in vitro antioxidant assays are routinely used to screen for biologically active compounds present in algal extracts when the requirement is to identify samples for progression to more detailed biological scrutiny. Whilst a myriad of antioxidant assays have been developed, this present chapter aims to give step-by-step practical guidance on how to carry out some of the most popular and biologically relevant assays at the bench.

On the radical scavenging activity of isoflavones: thermodynamics of O-H bond cleavage

We have performed Density Functional Theory B3LYP/6-311++G** calculations of reaction enthalpies of antioxidant action mechanisms for nine isoflavones. O-H bond dissociation enthalpies, ionization potentials, proton dissociation enthalpies, proton affinities and electron transfer enthalpies related to Hydrogen Atom Transfer (HAT), Single Electron Transfer-Proton Transfer (SET-PT) and Sequential Proton-Loss Electron-Transfer (SPLET) mechanisms were investigated in gas- and solution-phases. Studies on the radical scavenging ability of isoflavones, contrary to various flavonoids, are still scarce. Thus, understanding of its thermodynamics can be considered beneficial. The selection of isoflavones (daidzein, formononetin, genistein, biochanin A, prunetin, 6-hydroxydaidzein, glycitein, orobol and santal) enables us to evaluate the effects of various structural features, such as the presence of methoxy (4'-OMe, 6-OMe, 7-OMe) and hydroxy (3'-OH, 5-OH, 6-OH) groups, on studied reaction enthalpies. The obtained results show that HAT can be attributed predominantly to the B ring, while SPLET takes place preferentially in the A ring, as was also indicated in experimental works.

Contribution of major lipophilic antioxidants to the antioxidant activity of basil extracts: an EPR study

BACKGROUND

The present research analyses the contribution of some lipid antioxidants to the antioxidant activity of lipophilic extracts from basil by an electron paramagnetic resonance (EPR) study using the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). DPPH assay is considered an easy and accurate method with regard to measuring the antioxidant activity of plant extracts and EPR has already been employed to determine antioxidant activities of lipophilic plant extracts.

RESULTS

Lipid extracts were obtained from basil grown hydroponically for 20 or 35 days from sowing and in soil for 35 days from sowing. Fast and slow rate constants were distinguishable in the decay kinetics of DPPH mixture added with lipid extract. Antioxidants with kinetics characterized by a fast decay rate were tocopherols and chlorophylls, whereas those characterized by a slow decay rate were carotenoids, among which were β-carotene, lutein, β-apo-8'-carotenal and zeaxanthin. The 20-day hydroponically grown sample, which showed higher contents of tocopherol, chlorophyll and carotenoid molecules, was the sample endowed with the higher content of fast lipophilic antioxidants (FLA) and slow lipophilic antioxidants (SLA).

CONCLUSION

The three samples showed different compositions of FLA and SLA, giving rise to different decay kinetics. Despite the differences, in all samples tocopherol contributed about 0.3% to the bulk of FLA, whereas the figure for chlorophyll was about 40%, evidencing the relevant but little-studied role of chlorophyll as an antioxidant.

Distribution and reactivity of gallates toward galvinoxyl radicals in SDS micellar solutions — Effect of the alkyl chain length

In this work, we have evaluated the reactivity of methyl gallate, propyl gallate, and n-octyl gallate toward galvinoxyl radicals in homogeneous solution (ethanol) and sodium dodecyl sulfate micelles. In ethanol, the rate of galvinoxyl consumption was independent of the gallate’s alkyl chain length. On the other hand, reaction rates in micelles were dependent on the length of the gallate alkyl chain. Measurements of the rate of the reaction at different pH show that, even at pH 7.0, the reaction mainly involves the monodeprotonated anionic form of the gallates. Plots of reaction rates as a function of the surfactant concentration allowed us to evaluate the distribution of the gallates (KGH) and an apparent rate constant defined by the product between the intramicellar rate constant of the anion ([Formula: see text]) and its partition constant ([Formula: see text]). The values of the increment of the apparent rate constant per methylene group in the alkyl chain strongly suggest that intramicellar rate constant values are independent of the alkyl chain length. This points to a similar intramicellar localization of the phenolate moiety in the three gallates considered.