The importance of solvent type in estimating antioxidant properties of phenolic compounds by ABTS assay

Supramolecular DNA-based catalysis in organic solvents

The distinct folding accompanied by its polymorphic character renders DNA G-quadruplexes promising biomolecular building blocks to construct novel DNA-based and supramolecular assemblies. However, the highly polar nature of DNA limits the use of G-quadruplexes to water as a solvent. In addition, the archetypical G-quadruplex fold needs to be stabilized by metal-cations, which is usually a potassium ion. Here, we show that a noncovalent PEGylation process enabled by electrostatic interactions allows the first metal-free G-quadruplexes in organic solvents. Strikingly, incorporation of an iron-containing porphyrin renders the self-assembled metal-free G-quadruplex catalytically active in organic solvents. Hence, these "supraG4zymes" enable DNA-based catalysis in organic media. The results will allow the broad utilization of DNA G-quadruplexes in nonaqueous environments.

Synthesis of New Multifunctional Linolenic Acid Vanillyl Ester and Investigation of Antioxidant and Antibacterial Activities

Vanillyl alcohol (VA) possesses potent antioxidant activity, yet its applicability is hindered by its limited solubility in emulsions or non-polar organic solvents. Conversely, long-chain polyunsaturated fatty acids exhibit antibacterial properties. The combination of these compounds offers the prospect of developing novel phenolic lipid compounds with dual antioxidant and antibacterial activities, alongside enhanced solubility capabilities. In this investigation, linolenic acid vanillyl ester (LAVE) was synthesized from VA and linseed oil (LO) through a transesterification reaction employing immobilized lipase. Optimization of LAVE production was achieved by varying reaction temperature, substrate concentration, and reaction time. LAVE demonstrated efficacy in scavenging both 2,2-diphenyl-1-picryhydrazyl and 2,2'-azino-bis (3-ethylbenthiazoline-6-sulphonic acid) radicals in organic solvents. Antioxidant testing via lipid oxidation analysis revealed that LAVE, when distributed within emulsions, effectively impeded the formation of conjugated dienes and conjugated trienes. Furthermore, LAVE exhibited antibacterial activity against four strains of spoilage bacteria: Bacillus subtilis, Bacillus coagulans, Pseudomonas fluorescens, and Alcaligenes faecalis. Zeta potential analysis substantiated the binding of LAVE to the bacterial cell surface. Propidium iodide uptake assay and fluorescence microscopy further elucidated that LAVE induces cell lysis by augmenting membrane permeability.

Effect of Adding Fermented Proso Millet Bran Dietary Fiber on Micro-Structural, Physicochemical, and Digestive Properties of Gluten-Free Proso Millet-Based Dough and Cake

The increasing demand for functional foods has pushed the food industry to produce fiber-enriched products. In this study, rheological, microstructural, physicochemical, and functional characteristics were investigated for whole proso millet dough and cake, fortified with fermented proso millet bran dietary fiber flour (F-DF). Results showed that proso millet flour is less absorbent and stable than the control group. Adding proso millet flour and F-DF reduced the elasticity of the dough and increased its hardness, but had no significant effect on viscosity, cohesion, and resilience. The microstructure analysis exhibited an unformed continuous network formation in proso millet dough. Analyses suggested that proso millet flour combined with the fermented dietary fiber group had significantly higher total phenol content (0.46 GAE mg/g), DPPH• scavenging activity (66.84%), and ABTS•+ scavenging activity (87.01%) than did the other group. In addition, F-DF led to a significant reduction in the predicted released glucose contents of reformulated cakes. In summary, cakes prepared with the involvement of whole proso millet flour and F-DF exhibited less adverse sensory impact and possessed the potential to decrease postprandial blood glucose levels resulting purely from cake consumption.

Dryopteris juxtapostia Root and Shoot: Determination of Phytochemicals; Antioxidant, Anti-Inflammatory, and Hepatoprotective Effects; and Toxicity Assessment

An estimated 450 species of Dryopteris in the Dryoperidaceae family grow in Japan, North and South Korea, China, Pakistan, and Kashmir. This genus has been reported to have biological capabilities; however, research has been conducted on Dryopteris juxtapostia. Therefore, with the present study, we aimed to exploring the biological potential of D. juxtapostia root and shoot extracts. We extracted dichloromethane and methanol separately from the roots and shoots of D. juxtapostia. Antioxidant activity was determined using DPPH, FRAP, and H2O2 assays, and anti-inflammatory activities were evaluated using both in vitro (antiurease activity) and in vivo (carrageenan- and formaldehyde-induced paw edema) studies. Toxicity was evaluated by adopting a brine shrimp lethality assay followed by determination of cytotoxic activity using an MTT assay. Hepatoprotective effects of active crude extracts were examined in rats. Activity-bearing compounds were tentatively identified using LC-ESI-MS/MS analysis. Results suggested that D. juxtapostia root dichloromethane extract exhibited better antioxidant (DPPH, IC50 of 42.0 µg/mL; FRAP, 46.2 mmol/g; H2O2, 71% inhibition), anti-inflammatory (urease inhibition, 56.7% at 50 µg/mL; carrageenan-induced edema inhibition, 61.7% at 200 µg/mL; formaldehyde-induced edema inhibition, 67.3% at 200 µg/mL), brine shrimp % mortality (100% at 1000 µg/mL), and cytotoxic (HeLa cancer, IC50 of 17.1 µg/mL; prostate cancer (PC3), IC50 of 45.2 µg/mL) effects than D. juxtapostia root methanol extract. D. juxtapostia shoot dichloromethane and methanol extracts exhibited non-influential activity in all biological assays and were not selected for hepatoprotective study. D. juxtapostia root methanol extract showed improvement in hepatic cell structure and low cellular infiltration but, in contrast the dichloromethane extract, did not show any significant improvement in hepatocyte morphology, cellular infiltration, or necrosis of hepatocytes in comparison to the positive control, i.e., paracetamol. LC-ESI-MS/MS analysis showed the presence of albaspidin PP, 3-methylbutyryl-phloroglucinol, flavaspidic acid AB and BB, filixic acid ABA and ABB, tris-desaspidin BBB, tris-paraaspidin BBB, tetra-flavaspidic BBBB, tetra-albaspidin BBBB, and kaempferol-3-O-glucoside in the dichloromethane extract, whereas kaempferol, catechin, epicatechin, quinic acid, liquitrigenin, and quercetin 7-O-galactoside in were detected in the methanol extract, along with all the compounds detected in the dichloromethane extract. Hence, D. juxtapostia is safe, alongside other species of this genus, although detailed safety assessment of each isolated compound is obligatory during drug discovery.

Comparison of the antioxidant properties of serum and plasma samples as well as glutathione under environmental and pharmacological stress factors involving different classes of drugs

We compared the antioxidant activity of serum and plasma samples of a known glutathione content with the activity of glutathione, whilst determining to what extent various stress factors might change the activity of the tested samples. Copper ions and benzene were used as examples of environmental stress factors, and xenobiotics in the form of representatives of various groups of drugs, were used as examples of pharmacological stressors at therapeutic ranges. The activity was assessed by the ABTS, ORAC, FRAP and CUPRAC methods. Glutathione content was measured by the HPLC-FD method. During the experiments, plasma samples were shown to be more resistant to oxidative stress. Moreover, the important role of environmental xenobiotics in oxidative stress was revealed, as well as the differentiated influence of pharmaceutical xenobiotics. Among all pharmaceutical xenobiotics tested, including representatives of antiarrhythmic, antiepileptic, cytostatic and mucolytic drugs, the greatest stress was shown for antiarrhythmic drugs and cytostatics.

Some Particularities of the Reaction between Antioxidant Phenolic Acids and the Free Radical ABTS•+: a Comparative DFT Study for the Gas Phase and Ethanol

The detailed mechanism of the interaction of the radical cation ABTS•+ with a number of food acids (gallic, ferulic, caffeic, vanillic, cinnamic, syringic, p-coumaric) is revealed by means of the DFT calculations. It is shown that the interaction between the neutral molecules of the studied food acids and ABTS•+ does not lead to any charge transfer from these molecules onto ABTS•+. The almost complete conversion of the ABTS radical cation into its diamagnetic derivative occurs due to the interaction of one of the sulphonic groups of ABTS•+ with the acid anions through the formation of the corresponding intermolecular hydrogen bond.

Soft Magnetic Microrobot Doped with Porous Silica for Stability-Enhanced Multimodal Locomotion in a Nonideal Environment

As an emerging field of robotics, magnetic-field-controlled soft microrobot has broad application prospects for its flexibility, locomotion diversity, and remote controllability. Magnetic soft microrobots can perform multimodal locomotion under the control of a magnetic field, which may have potential applications in precision medicine. However, previous research studies mainly focus on new locomotion in a relatively ideal environment, lacking exploration on the ability of magnetic microrobot locomotion to resist external disturbances and proceed in a nonideal environment. Here, a porous silica-doped soft magnetic microrobot is constructed for enhanced stability of multimodal locomotion in the nonideal biological environment. Porous silica spheres are doped into a NdFeB-silicone elastomer base, improving adhesion properties and refining the comprehensive mechanical properties of the microrobot. Multimodal locomotions are achieved, and the influence of porous silica doping on the stability of each locomotion in a nonideal environment is explored in depth. Motions in nonideal circumstances such as climbing, loading, current rushing, wind blowing, and obstacle hindering are conducted successfully with porous silica doping. Such a stability-enhanced multimodal locomotion system can be used in biocatalysis and thrombus removal, and its prospect for precision medicine is highlighted by in vivo demonstration of multimodal locomotion with nonideal disturbance.

Chemical and Biochemical Characterization of Essential Oils and Their Corresponding Hydrolats from Six Species of the Lamiaceae Family

Many plants belonging to the Lamiaceae family are rich in essential oils (EOs) which are intensively used for aromatherapy, food and beverage flavoring, alternative medicine, cosmetics, and perfumery. Aerial parts of Thymus vulgaris L., Thymus pannonicus All., Lavandula angustifolia L., Lavandula x intermedia, Origanum vulgare L., and Origanum vulgare var. aureum L. were subjected to hydrodistillation, and both resulting fractions were analyzed. The purpose of this study was to determine the chemical composition, antioxidant activity, and total phenolic content of six essential oils and their corresponding hydrolats (HDs) through GC-MS and spectrophotometric analyses. Overall, 161 compounds were identified, some found exclusively in essential oils and others in hydrolats, making them individual products with specific end purposes. The total phenolic content was the highest for the Thymus vulgaris L. EOs (3022 ± mg GAE L-1), because of its high phenolic oxygenated monoterpenes content (thymol and carvacrol) and the smallest for the Lavandula angustifolia L. EOs (258.31 ± 44.29 mg GAE L-1), while hydrolats varied from 183.85 ± 0.22 mg GAE L-1 for Thymus vulgaris L. HD and 7.73 mg GAE L-1 for Thymus pannonicus All. HD. Significant antioxidant effects determined through DPPH• and ABTS•+ assays were also observed in samples with higher hydrophilic compounds. The highest antioxidant activity was determined for Thymus vulgaris L. EO and its corresponding HD. Although EOs are the principal traded economic product, HDs represent a valuable by-product that could still present intense antiseptic activities, similar to their corresponding EOs (thyme and oregano), or have multiple aromatherapy, cosmetics, and household applications (lavender and lavandin).

How to express the antioxidant properties of substances properly?

Oxidative stress, associated with an imbalance between the oxidants (reactive oxygen species) and the antioxidants in the body, contributes to the development of many diseases. The body’s fight against reactive oxygen species is supported by antioxidants. Nowadays, there are too many analytical methods, but there is no one universal technique for assessing antioxidant properties. Moreover, the applied different ways of expressing the results lead to their incompatibility and unreasonable interpretation. The paper is a literature review concerning the most frequent ways of antioxidant activities expression and for an easy and universal method of the obtained results discussion. This paper is an attempt to point out their disadvantages and advantages. The manuscript can support the searching interpretation of the obtained results which will be a good tool for the development of a number of fields, especially medicine what can help in the future detection and treatment of many serious diseases.

Graphic abstract

Green Synthesis, Characterization, and Antibacterial Properties of Silver Nanoparticles Obtained by Using Diverse Varieties of Cannabis sativa Leaf Extracts

Cannabis sativa L. (hemp) is a plant used in the textile industry and green building material industry, as well as for the phytoremediation of soil, medical treatments, and supplementary food products. The synergistic effect of terpenes, flavonoids, and cannabinoids in hemp extracts may mediate the biogenic synthesis of metal nanoparticles. In this study, the chemical composition of aqueous leaf extracts of three varieties of Romanian hemp (two monoecious, and one dioecious) have been determined by Fourier-Transformed Infrared spectroscopy (FT-IR), high-performance liquid chromatography, and mass spectrometry (UHPLC-DAD-MS). Then, their capability to mediate the green synthesis of silver nanoparticles (AgNPs) and their pottential antibacterial applications were evaluated. The average antioxidant capacity of the extracts had 18.4 ± 3.9% inhibition determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and 78.2 ± 4.1% determined by 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS™) assays. The total polyphenolic content of the extracts was 1642 ± 32 mg gallic acid equivalent (GAE) L-1. After this, these extracts were reacted with an aqueous solution of AgNO3 resulting in AgNPs, which were characterized by UV-VIS spectroscopy, FT-IR, scanning electron microscopy (SEM-EDX), and dynamic light scattering (DLS). The results demonstrated obtaining spherical, stable AgNPs with a diameter of less than 69 nm and an absorbance peak at 435 nm. The mixture of extracts and AgNPs showed a superior antioxidant capacity of 2.3 ± 0.4% inhibition determined by the DPPH• assay, 88.5 ± 0.9% inhibition as determined by the ABTS•+ assay, and a good antibacterial activity against several human pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas fluorescens, and Staphylococcus aureus.

Constituents of Chamaecrista diphylla (L.) Greene Leaves with Potent Antioxidant Capacity: A Feature-Based Molecular Network Dereplication Approach

Chamaecrista diphylla (L.) Greene (Fabaceae/Caesalpiniaceae) is a herbaceous plant that is widely distributed throughout the Americas. Plants from this genus have been used in traditional medicine as a laxative, to heal wounds, and to treat ulcers, snake and scorpion bites. In the present study, we investigated the chemical composition of Chamaecrista diphylla leaves through a mass spectrometry molecular network approach. The oxygen radical absorbance capacity (ORAC) for the ethanolic extract, enriched fractions and isolated compounds was assessed. Overall, thirty-five compounds were annotated for the first time in C. diphylla. Thirty-two of them were reported for the first time in the genus. The isolated compounds 9, 12, 24 and 33 showed an excellent antioxidant capacity, superior to the extract and enriched fractions. Bond dissociation energy calculations were performed to explain and sustain the antioxidant capacity found. According to our results, the leaves of C. diphylla represent a promising source of potent antioxidant compounds.

CBG, CBD, Δ9-THC, CBN, CBGA, CBDA and Δ9-THCA as antioxidant agents and their intervention abilities in antioxidant action

Positive effect of some cannabinoids in the treatment and prophylaxis of a wide variety of oxidation-associated diseases and growing popularity of supplements containing cannabinoids, mainly cannabinoid oils (e.g. CBD oil, CBG oil), in the self-medication of humans cause a growing interest in the antioxidant properties of these compounds, especially those not showing psychotropic effects. Herein, we report the antioxidant activity of cannabigerol (CBG), cannabidiol (CBD), Δ9-tetrahydrocannabinol (Δ9-THC), cannabinol (CBN), cannabigerolic acid (CBGA), cannabinolic acid (CBDA) and Δ9-tetrahydrocannabinolic acid (Δ9-THCA) estimated by spectrophotometric methods: ABTS, DPPH, ORAC, beta-carotene CUPRAC and FRAP. The presented data prove that all the examined cannabinoids exhibit antioxidant activity manifested in their ability to scavenge free radicals, to prevent the oxidation process and to reduce metal ions. Although the intensity of these activities is not the same for the individual cannabinoids it is comparable for all of them with that of E vitamin. As results from the research, the significance of the two types of electron sources presenting in examined cannabinoids, phenolic groups and double bonds transferring electrons, depends on the type of electron-accepting species - radicals/metal ions.

Techniques and modeling of polyphenol extraction from food: a review

There is a growing demand for vegetal food having health benefits such as improving the immune system. This is due in particular to the presence of polyphenols present in small amounts in many fruits, vegetables and functional foods. Extracting polyphenols is challenging because extraction techniques should not alter food quality. Here, we review technologies for extracting polyphenolic compounds from foods. Conventional techniques include percolation, decoction, heat reflux extraction, Soxhlet extraction and maceration, whereas advanced techniques are ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, high-voltage electric discharge, pulse electric field extraction and enzyme-assisted extraction. Advanced techniques are 32-36% more efficient with approximately 15 times less energy consumption and producing higher-quality extracts. Membrane separation and encapsulation appear promising to improve the sustainability of separating polyphenolic compounds. We present kinetic models and their influence on process parameters such as solvent type, solid and solvent ratio, temperature and particle size.

Abiotic stress combinations improve the phenolics profiles and activities of extractable and bound antioxidants from germinated spelt (Triticum spelta L.) seeds

The aim of this study was to investigate the effects of germination of spelt seeds under different stress conditions on the antioxidant characteristics of their extractable and bound phenolics. Germination under combined stress of 25 mM NaCl and 50 mM sorbitol without subsequent mechanical stress had considerable impact on total phenolics contents and scavenging activities against different free radicals (DPPH, ABTS⁺, O₂^-, ROO). Alkaline hydrolysis of extracts from germinated seeds provided the majority of their phenolic acids, where ferulic and p-coumaric acids were the most representative. The phenolics liberated from their bound form also had greater antioxidant activities. For the extractable phenolics, p-coumaric hexoside increased the most (146%), while among the bound phenolics identified, the highest relative increase was for p-coumaric acid (171%). The germinated seeds showed no effects on intracellular oxidation in cells of the yeast Saccharomyces cerevisiae.

The Sirtuin-1 relied antioxidant and antiaging activity of 5,5'-diferulic acid glucoside esters derived from corn bran by enzymatic method

Maize is the food crop with the highest total output in the world. However, corn bran is only a by-product with low price. The 5,5'-diferulic acid glucoside esters (DFG) were obtained from corn bran using the enzymatic method. DFG showed obvious antioxidant capacity in cell, Caenorhabditis elegans (C. elegans) and in mouse. DFG decreased ROS and MDA content in 500 μM H₂ O₂ stimulated ARPE-19 cells to 48.6% and 32.2%, respectively. DFG decreased ROS content in C. elegans to 49.1% and MDA content in acute ethanol (50%, 12 ml/kg) stimulated mouse to 30.4%. DFG also increased SOD protein content significantly in cell, C. elegans and mouse to 175.5%, 120.1%, and 126.2%, respectively. DFG significantly extended the lifespan of C. elegans both under heat stress and natural situation. The median survival time was prolonged to 133.3% and 116.7%, respectively. This capacity relied on the SIR-2.1 activity. SIR-2.1 is an ortholog of human Sirtuin-1 (SIRT-1). DFG also upregulated SIRT-1 and PCG-1α expression level obviously in H₂ O₂ -stimulated ARPE-19 cells (to 134.4% and 127.1%, respectively) and in acute ethanol stimulated mouse eyes (to 135.1% and 111.5%, respectively) and liver (to 123.3% and 113.6%, respectively). These results indicate that DFG has multiple bioactivities. Our research provides a new application prospect of corn bran. And to our best knowledge, this is the first time, the sirtuins-relied lifespan extension activity of the 5,5'-diferulic acid extracted from corn bran was reported. PRACTICAL APPLICATIONS: The traditional method for extracting diferulic acid from corn bran is to use the strong alkali. Obviously, this is not welcomed by the food industry. We employed the biological enzyme method in a relatively mild pH range during the extraction process. It is more environmentally friendly and more economical. DFG can be added as a raw material for functional foods like yogurt, fruit juice, and cereals. As well, the solid precipitate obtained after extraction can also be used as high-quality dietary fiber to produce functional food. Meanwhile, concerning for the 5,5'-diferulic acid derived from corn bran, the relevant research is still not abundant. And to our best knowledge, we have reported for the first time about the effect of this kinds of diferulic acid on prolonging life span and its SIRT-1-dependent activity. It also provides a new perspective for the study of diferulic acid.

Flavonoids with Glutathione Antioxidant Synergy: Influence of Free Radicals Inflow

This report explores the antioxidant interaction of combinations of flavonoid–glutathione with different ratios. Two different 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid radical (ABTS^•+)-based approaches were applied for the elucidation of the antioxidant capacity of the combinations. Despite using the same radical, the two approaches employ different free radical inflow systems: An instant, great excess of radicals in the end-point decolorization assay, and a steady inflow of radicals in the lag-time assay. As expected, the flavonoid–glutathione pairs showed contrasting results in these two approaches. All the examined combinations showed additive or light subadditive antioxidant capacity effects in the decolorization assay. This effect showed slight dilution dependence and did not change when the initial ABTS^•+ concentration was two times as high or low. However, in the lag-time assay, different types of interaction were detected, from subadditivity to considerable synergy. Taxifolin–glutathione combinations demonstrated the greatest synergy, at up to 112%; quercetin and rutin, in combination with glutathione, revealed moderate synergy in the 30–70% range; while morin–glutathione appeared to be additive or subadditive. In general, this study demonstrated that, on the one hand, the effect of flavonoid–glutathione combinations depends both on the flavonoid structure and molar ratio; on the other hand, the manifestation of the synergy of the combination strongly depends on the mode of inflow of the free radicals.

Aluminium accumulation in excess and related anti-oxidation responses in C4 weed (Amaranthus viridis L.)

C₄ species, Amaranthus viridis L. exhibited a significant bioaccumulation of aluminium (Al) through the duration of 3- and 5-days exposure. As compared to control, Amaranthus appeared as excess-accumulator with maximum 5.85-fold bioaccumulation of Al in root. Cellular responses to Al tolerance initially scored tissue specific distribution of metal through cortical layers revealed by electron microscopy. The affected cells changed an oxidative status as read by histochemical stains, particularly, for hydrogen peroxide. Osmotic stress and its stability were scored by maximum proline and free amino acids accumulation with 1.53 and 1.59-fold increase over control. The accumulation of phenolics and flavonoids were over expressed in the ranges of 2.48-2.50-fold and 2.00-1.5-fold at 3- and 5-days respectively against control. Anti-oxidation to detoxify Al stress was facilitated by variants of peroxidases. For exclusion mechanism of metal, esterase activity significantly over expressed with maximum value of 1.80-fold at 5-days. The polymorphism of esterase exhibited few significant over produced bands, varied in numbers as detected by densitometric scanning. Moreover, plant extract was satisfactorily potential under in vitro anti-oxidation systems through assay of 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS), ferric chelation activity etc. Therefore, weeds like Amaranthus would be a bioprospecting in role likely involved in phytoremediation of metal.

Effects of cooking on the phytochemical profile of breadfruit as revealed by high-resolution UPLC-MSE

BACKGROUND

This study evaluated the impact of cooking on the profile of bioactive compounds in unripe breadfruit. To this end, the accessibility of bioactive compounds by various solvents was assessed through total phenolic content and antioxidant capacity analyses. The most efficient solvent was applied to extract the metabolites, which were evaluated by ultra-performance liquid chromatography coupled with high-resolution quadrupole time-of-flight mass spectrometry in MS^E mode.

RESULTS

Cooked and raw breadfruit presented total phenolic content and antioxidant capacities in almost all extracts, and pure water proved to be the best extractor. Globally, 146 bioactive compounds have been identified for both raw and cooked fruits' aqueous extracts. Most of these compounds were stable to the heat treatment applied (121 °C/10 min). However, results revealed that 22 metabolites contributed to significantly distinguishing the raw from the cooked samples. Among those, 15 compounds, such as pyrogallol, 1-acetoxypinoresinol, and scopolin, evidenced higher relative abundance in the cooked extracts. On the other hand, only seven metabolites, such as 4-hydroxyhippuric acid, epicatechin, and leptodactylone, decreased post-heating.

CONCLUSIONS

Cooking promoted little alteration in the bioactive compounds profile of immature breadfruit and thus appears to be an exploitation alternative for this perishable fruit, which seems to be a source of a large range of bioactive compounds. © 2019 Society of Chemical Industry.

Antioxidant Recovery from Pomegranate Peel Waste by Integrating Maceration and Freeze Concentration Technology

Pomegranate peel, a by-product of pomegranate fruit is rich in antioxidants. It is being used as an animal feed or discarded to the environment, which could cause an environmental problem. A new integrated process of maceration and freeze concentration was studied to recover the antioxidants from the pomegranate peel. The low temperature used in the freeze concentration assists in concentrating a high quality of antioxidants. The concentrated peel solution was tested for an antioxidant activity via 2,2 diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method. It was found that methanol gave the best extraction of antioxidants from pomegranate peel. The highest antioxidant recovery with DPPH radical scavenging of 96.14 % was obtained at −16 °C of coolant temperature and 30 min of freezing time (p < 0.05). The integrated process has proven to be an effective method to recover the antioxidants from pomegranate peel and can be applied to recover other bioactive compounds.

ABTS/PP Decolorization Assay of Antioxidant Capacity Reaction Pathways

The 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS^•+) radical cation-based assays are among the most abundant antioxidant capacity assays, together with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-based assays according to the Scopus citation rates. The main objective of this review was to elucidate the reaction pathways that underlie the ABTS/potassium persulfate decolorization assay of antioxidant capacity. Comparative analysis of the literature data showed that there are two principal reaction pathways. Some antioxidants, at least of phenolic nature, can form coupling adducts with ABTS^•+, whereas others can undergo oxidation without coupling, thus the coupling is a specific reaction for certain antioxidants. These coupling adducts can undergo further oxidative degradation, leading to hydrazindyilidene-like and/or imine-like adducts with 3-ethyl-2-oxo-1,3-benzothiazoline-6-sulfonate and 3-ethyl-2-imino-1,3-benzothiazoline-6-sulfonate as marker compounds, respectively. The extent to which the coupling reaction contributes to the total antioxidant capacity, as well as the specificity and relevance of oxidation products, requires further in-depth elucidation. Undoubtedly, there are questions as to the overall application of this assay and this review adds to them, as specific reactions such as coupling might bias a comparison between antioxidants. Nevertheless, ABTS-based assays can still be recommended with certain reservations, particularly for tracking changes in the same antioxidant system during storage and processing.

What is responsible for antioxidant properties of polyphenolic compounds from plants?

Due to the negative impact of reactive species (including free radicals) on humans and animals, the investigations to find effective substances (antioxidants), which protect living organisms against their damaging influence are carried out throughout the world. As most widespread synthetic antioxidants are suspected of having a noxious effect on the human body, more and more attention is paid to natural antioxidant compounds found in plants (especially phenolic compounds). The aim of this paper is to present the data about antioxidant activity of polyphenolic compounds with the emphasis on the main factors having influence on their antioxidant activity: chemical structure, ability to form hydrogen bonds, capability of metal ions chelation and reduction, adduct formation, kinetic solvents effect, mechanism of antioxidant reaction, capability of antioxidant enzyme activation and reduction potential.

Lipase-mediated synthesis of ricinoleic acid vanillyl ester and evaluation of antioxidant and antibacterial activity

Castor oil extracted from castor bean has antibacterial property, and has been used in various folk remedies. The major structural component of castor oil, ricinoleic acid, has actual antibacterial activity. Some phenolic compounds derived from plants have antioxidant property. Among them, vanillyl alcohol from vanilla bean has strong antioxidant activity. As vanillyl alcohol has low solubility in hydrophobic solvents and castor oil has low solubility in hydrophilic solvents, there is practical difficulty in using them. We performed lipase-mediated transesterification using vanillyl alcohol and castor oil, and synthesized ricinoleic acid vanillyl ester (RAVE). 2,2-Diphenyl-1-picrylhydrazyl assay and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) assay revealed that RAVE had a strong antioxidant activity in various organic solvents. RAVE also had antibacterial activity against some food spoilage bacteria. It showed more powerful antibacterial activity for gram positive bacteria than for gram negative bacteria. The critical micelle concentration of RAVE was measured at 7.36 μM and it partitioned exclusively into emulsion phase in water-emulsion system. Zeta potential measurement, membrane release test, and fluorescent microscopy showed that RAVE inserted itself into the bacterial cell membrane, destroyed membrane permeability, and induced cell death. As such, RAVE is a novel multi-functional compound with antioxidant and antibacterial activity, so it can be used as a functional material in the food and cosmetic industries.

Antioxidant Profile of 1-Monocaffeoyl Glycerol in Lipophobic/Lipophilic Media

Oxidative stress has been generally considered as one trigger of organism imbalance, resulting in lipid peroxidation, DNA damage and protein oxidation, which could be relieved by antioxidant supplement or endogenous antioxidant system. In present study, 1-monocaffeoyl glycerol (1-MCG), an amphipathic caffeic acid natural derivative, was enzymatically synthesized by Lipozyme 435, and its antioxidant profile in both lipophilic and lipophobic media was evaluated. The 1-MCG was identified by HPLC-UV, HPLC-ESI-MS, and ¹ H/¹³ C-NMR. Subsequently, antioxidant assays in lipophilic (DPPH assay) and lipophobic (ABTS, ORAC, erythrocyte hemolysis, ROS, MDA, and GPx assays) systems were explored. The better and lasting DPPH· and ABTS^+· inhibitions of 1-MCG than caffeic acid (CA) were related to its better solubilities in ethanol/water media and electron transfer ability. ORAC results suggested the radical scavenging activities of 1-MCG (5 to 40 µM) were higher than Trolox. Furthermore, the effectiveness of 1-MCG against AAPH-induced erythrocytes oxidation indicated that 1-MCG can effectively inhibit hemolysis. ESEM was also applied to verify the hemolysis inhibition and morphology preservation abilities of 1-MCG. Besides, results showed 1-MCG was able to prevent ROS from invasion, reduce production of MDA, up-regulated GPx activity, terminate lipid peroxidation, and maintain the integrity of the structure and function of erythrocytes. PRACTICAL APPLICATION: As an amphiphilic caffeic acid derivative, 1-monocaffeoyl glycerol was synthesized, purified, and identified. 1-Monocaffeoyl glycerol could significantly eliminate radicals including DPPH·, ABTS^+· , and AAPH in ethanol, water, and PBS system, respectively. 1-Monocaffeoyl glycerol could protect erythrocyte from AAPH induced hemolysis.

Extraction Process, Component Analysis, and In Vitro Antioxidant, Antibacterial, and Anti-Inflammatory Activities of Total Flavonoid Extracts from Abutilon theophrasti Medic. Leaves

The flavonoid fraction was extracted from the leaves of Abutilon theophrasti Medic., which are usually used as a traditional Chinese herbal medicine for the treatment of inflammation and joint pain. The current study focused on the extraction process, component analysis, and in vitro antioxidant, antibacterial, and anti-inflammatory activities of the flavonoid fraction as a part of ongoing research on bioactive substances from natural plant sources. This study evaluated the antioxidant activities via assays of DPPH radical scavenging capacity, ABTS radical scavenging capacity, and reducing power and investigated inhibitory activities against Escherichia coli, Salmonella, Staphylococcus aureus, and Streptococcus. Moreover, the inflammatory activity of the flavonoid fraction was estimated by measurement of the content of tumor necrosis factor alpha, interleukin-1-beta, interleukin-6, interleukin-10, nitric oxide, and cyclooxygenase-2 and the gene expression levels of several inflammation markers, such as inducible nitric oxide synthase and cyclooxygenase-2, in RAW 264.7 macrophages after LPS treatment. In addition, the underlying anti-inflammatory mechanisms, that is, the activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways, were also revealed from the gene and protein expression levels. Taken together, these results suggested that the flavonoid fraction might exert in vitro antioxidant, antibacterial, and anti-inflammatory effects on LPS-stimulated RAW 264.7 macrophages and will be potentially useful as an adjuvant treatment for oxidative stress and bacterial and inflammatory diseases.

Extraction optimization, preliminary characterization and antioxidant activities of polysaccharides from Glycine soja

Single-factor experiment and Central Composite Design (CCD) was applied to optimize the ultrasound-assisted extraction (UAE) conditions of polysaccharides from Glycine soja (CGPS), and a preliminary characterization of three polysaccharide fractions (CGPS, GPS-1, and GPS-2) and their antioxidant activities were investigated. Under the optimal conditions: ratio of liquid to solid 42.7mL/g, extraction power 293.7W, extraction temperature 68.9°C, and extraction time 34.7min, the experimental CGPS yield was 6.04mg/g. CGPS was further purified by DEAE-cellulose and Sephadex-100 chromatography to obtain two fractions (GPS-1 and GPS-2), and their monosaccharides compositions were characterized by HPLC. Fourier-transform infrared spectra (FT-IR) indicated the chemical structures of them. Moreover, they exhibited high antioxidant activities in a concentration-dependent manner in vitro. In summary, the present study suggested that UAE was a very effective method to extract polysaccharides from Glycine soja and the polysaccharides could be explored as potential antioxidant agents for medicine and function food.

Re-evaluation of ABTS•+ Assay for Total Antioxidant Capacity of Natural Products

2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation (ABTS•+) is a stable free radical frequently used for estimating the total antioxidant capacity (TAC) of natural products. The existing methods for ABTS•+ radical-scavenging activity assays are diverse in pre-diluting solvents and reaction time, which lead to errors in the TAC estimations. To develop an effective and universal method for estimating the ABTS•+ capacity accurately and reasonably, five pre-dilution solvents [methanol, ethanol, phosphate buffer (Na2HPO4-NaH2PO4, 200 mM, pH = 7.4), PBS buffer (Na2HPO4-NaH2PO4-NaCl, 200 mM, pH = 7.4), and distilled water] and different reaction times were investigated in ABTS•+ assays of five typical antioxidants. The results showed that the solvent effects were very significant. When using different pre-diluting solvents, different detection wavelengths should be selected. ABTS-+ assay could be measured within 2–10 min to obtain a rough result, which was mostly 6 min in the literature. However, full and accurate evaluation of antioxidant reactivity rather than capacity requires recording ABTS•+ loss continuously during the whole reaction period. The present study makes a recommendation for estimating the ABTS•+ capacity accurately and reasonably.

Isolation and characterization of new phenolic compounds with estrogen biosynthesis-inhibiting and antioxidation activities from Broussonetia papyrifera leaves

Broussonetia papyrifera leaves (BPL) as a traditional Chinese medicine are also used in livestock feed for stimulating reproduction, adipose tissue and muscle development; however, the mechanism of their action is still unknown. Through estrogen biosynthesis-guided fractionation in human ovarian granulosa-like KGN cells, five new phenolic glycosides, broussoside A–E(1–5), along with fifteen known dietary phenolic compounds, were isolated from the n-butanol extract of BPL, and their structures were elucidated on the basis of NMR spectra analysis and chemical evidence. New compounds 3, 4, 5 and the known compounds 9 and 10 were found to potently inhibit estrogen biosynthesis in KGN cells. In addition, compounds 9, 17, 18, and 20 showed strong antioxidant activity against ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) and DPPH (1, 1′-diphenyl -2-picryl-hydrazyl radical) assays. These findings suggest that BPL may improve meat quality through the regulation of estrogen biosynthesis. Furthermore, they may be useful for the discovery of potential aromatase modulators from natural products. Finally, they could be considered as a new source for natural antioxidants.