Kinetic Potentiometry as a Method for Studying the Interactions of Antioxidants with Peroxyl Radicals

This work presents a new method using kinetic potentiometry to study the thermodynamic and kinetic parameters of the reactions of antioxidants with peroxyl radicals. The rate constants of the reaction of antioxidants with radicals have been determined, and the groups of "fast" and "slow" antioxidants have been conventionally distinguished. Fast antioxidants include ascorbic, uric, gallic, chlorogenic, caffeic acids, glutathione, L-cysteine, and catechol with constant values from (1.05-9.25) × 103 M·s-1; "slow" antioxidants are α-tocopherol (in aqueous media), ionol, 2,6-ditretbutylphenol, and compounds of the azoloazine series, modified with polyphenolic fragments, with constant values from (4.00-8.50) × 102 M·s-1. It is shown that the value of the rate constant is directly related to the type of kinetic dependence of the potential recorded when an antioxidant is introduced into the solution of the radical initiator. It is shown that the method with the determination of the induction period is difficult in the study of "slow" antioxidants. It has been established that the area above the curve of the kinetic dependence Exp(∆E) is directly related to the amount of inhibited peroxyl radicals and can be used to assess the inhibitory properties of an antioxidant from a thermodynamic point of view. "Fixed time method" and "Initial rate method" were used. Positive correlations between the described method have been established. The utility of the parameter of the area above the curve of the kinetic dependence Exp(∆E) in the study of objects of complex composition is shown.

Almond (Prunus dulcis) Bagasse as a Source of Bioactive Compounds with Antioxidant Properties: An In Vitro Assessment

The presence of components of nutritional interest makes fresh almond bagasse an interesting by-product for obtaining functional ingredients. Stabilization through a dehydration process is an interesting option for its integral use, ensuring its conservation and management. Subsequently, it can be turned into powder, facilitating its use as an ingredient. The aim of this paper was to determine the effects of hot air drying at 60 and 70 °C and lyophilization on the release of phenolic components and antiradical capacity in in vitro gastrointestinal digestion and colonic fermentation, as well as on growing microbiota composition by applying high throughput sequencing. The novelty of this study lies in this holistic approach; considering both technological and physiological aspects related to gastrointestinal digestion and colonic fermentation will provide the best conditions for functional foods. The results obtained showed that lyophilization provides a powder with a total phenol content and antiradical capacity higher than hot air drying. Furthermore, in dehydrated samples, both in vitro digestion and colonic fermentation revealed a phenol content and anti-radical capacity superior to those existing in undigested products. In addition, after colonic fermentation, beneficial bacteria species have been identified. Obtaining powders from almond bagasse is presented as an interesting opportunity for the valorization of this by-product.

Evaluation of Antioxidant and Anticancer Activity of Mono- and Polyfloral Moroccan Bee Pollen by Characterizing Phenolic and Volatile Compounds

Bee pollen is frequently characterized as a natural source of bioactive components, such as phenolic compounds, which are responsible for its pharmaceutical potential and nutritional properties. In this study, we evaluated the bioactive compound contents of mono- and polyfloral bee pollen samples using spectroscopic and chromatographic methods and established links with their antioxidant and antitumor activity. The findings demonstrated that the botanical origin of bee pollen has a remarkable impact on its phenolic (3-17 mg GAE/g) and flavonoid (0.5-3.2 mg QE/g) contents. Liquid chromatography-mass spectrometry analysis revealed the presence of 35 phenolic and 13 phenylamide compounds in bee pollen, while gas chromatography-mass spectrometry showed its richness in volatiles, such as hydrocarbons, fatty acids, alcohols, ketones, etc. The concentration of bioactive compounds in each sample resulted in a substantial distinction in their antioxidant activity, DPPH (EC₅₀: 0.3-0.7 mg/mL), ABTS (0.8-1.3 mM Trolox/mg), and reducing power (0.03-0.05 mg GAE/g), with the most bioactive pollens being the monofloral samples from Olea europaea and Ononis spinosa. Complementarily, some samples revealed a moderate effect on cervical carcinoma (GI₅₀: 495 μg/mL) and breast adenocarcinoma (GI₅₀: 734 μg/mL) cell lines. This may be associated with compounds such as quercetin-O-diglucoside and kaempferol-3-O-rhamnoside, which are present in pollens from Olea europaea and Coriandrum, respectively. Overall, the results highlighted the potentiality of bee pollen to serve health-promoting formulations in the future.

Salinity Stress Ameliorates Pigments, Minerals, Polyphenolic Profiles, and Antiradical Capacity in Lalshak

Previous studies have shown that salinity eustress enhances the nutritional and bioactive compounds and antiradical capacity (ARC) of vegetables and increases the food values for nourishing human diets. Amaranth is a salinity-resistant, rapidly grown C4 leafy vegetable with diverse variability and usage. It has a high possibility to enhance nutritional and bioactive compounds and ARC by the application of salinity eustress. Hence, the present study aimed to evaluate the effects of sodium chloride stress response in a selected Lalshak (A. gangeticus) genotype on minerals, ascorbic acid (AsA), Folin−Ciocalteu reducing capacity, beta-carotene (BC), total flavonoids (TF), pigments, polyphenolic profiles, and ARC. A high-yield, high-ARC genotype (LS6) was grown under conditions of 0, 25, 50, and 100 mM sodium chloride in four replicates following a block design with complete randomization. We recognized nine copious polyphenolic compounds in this accession for the first time. Minerals, Folin−Ciocalteu reducing capacity, AsA, BC, pigments, polyphenolic profiles, and ARC of Lalshak were augmented progressively in the order: 0 < 25 < 50 < 100 mM sodium chloride. At 50 mM and 100 mM salt concentrations, minerals, AsA, Folin−Ciocalteu reducing capacity, BC, TF, pigments, polyphenolic profiles, and ARC of Lalshak were much greater than those of the control. Lalshak could be used as valuable food for human diets as a potent antioxidant. Sodium chloride-enriched Lalshak provided outstanding quality to the final product in terms of minerals, AsA, Folin−Ciocalteu reducing capacity, BC, TF, pigments, polyphenolic profiles, and ARC. We can cultivate it as a promising alternative crop in salinity-prone areas of the world.

Design and Antioxidant Properties of Bifunctional 2H-Imidazole-Derived Phenolic Compounds-A New Family of Effective Inhibitors for Oxidative Stress-Associated Destructive Processes

The synthesis of inhibitors for oxidative stress-associated destructive processes based on 2H-imidazole-derived phenolic compounds affording the bifunctional 2H-imidazole-derived phenolic compounds in good-to-excellent yields was reported. In particular, a series of bifunctional organic molecules of the 5-aryl-2H-imidazole family of various architectures bearing both electron-donating and electron-withdrawing substituents in the aryl fragment along with the different arrangements of the hydroxy groups in the polyphenol moiety, namely derivatives of phloroglucinol, pyrogallol, hydroxyquinol, including previously unknown water-soluble molecules, were studied. The structural and antioxidant properties of these bifunctional 5-aryl-2H-imidazoles were comprehensively studied. The redox transformations of the synthesized compounds were carried out. The integrated approach based on single and mixed mechanisms of antioxidant action, namely the AOC, ARC, Folin, and DPPH assays, were applied to estimate antioxidant activities. The relationship “structure-antioxidant properties” was established for each of the antioxidant action mechanisms. The conjugation effect was shown to result in a decrease in the mobility of the hydrogen atom, thus complicating the process of electron transfer in nearly all cases. On the contrary, the conjugation in imidazolyl substituted phloroglucinols was found to enhance their activity through the hydrogen transfer mechanism. Imidazole-derived polyphenolic compounds bearing the most electron-withdrawing functionality, namely the nitro group, were established to possess the higher values for both antioxidant and antiradical capacities. It was demonstrated that in the case of phloroglucinol derivatives, the conjugation effect resulted in a significant increase in the antiradical capacity (ARC) for a whole family of the considered 2H-imidazole-derived phenolic compounds in comparison with the corresponding unsubstituted phenols. Particularly, conjugation of the polyphenolic subunit with 2,2-dimethyl-5-(4-nitrophenyl)-2H-imidazol-4-yl fragment was shown to increase ARC from 2.26 to 5.16 (10⁴ mol-eq/L). This means that the considered family of compounds is capable of exhibiting an antioxidant activity via transferring a hydrogen atom, exceeding the activity of known natural polyphenolic compounds.

Valorization of Arnica montana Wastes after Extraction of the Ethanol Tincture: Application in Polymer-Based Matrices

The waste solids remaining after the ethanolic extraction of arnica were proposed as raw material for the recovery of the remaining phenolic fraction. Greener processes based on intensification extraction, with microwave (MHG) and ultrasound (UAE) assistance and pressurized hot water extraction under subcritical conditions (AH), were studied. The entire process provided approximately 28% of phenolics for the sequence when MHG was used, 22% in the sequence where AH was employed, and the extracts showed up to 60% the ABTS radical scavenging capacity of Trolox. However, the cytotoxic effects on the cell growth of tumoral cells were only moderate. Therefore, considering a possible external topical application, extracts containing selected arnica extracts were further used to develop polymer-based gelled matrices formulated with either chitosan or polyvinyl alcohol. Rheological testing indicated that all proposed matrices exhibited relatively high mechanical features, even better than those determined with matrices prepared with their counterpart commercial arnica tinctures. Overall, the shear-thinning behavior of gelled matrices loaded with arnica extracts obtained by MHG or AH stages was enhanced compared to those containing ethanolic extracts, whereas the viscoelastic features became smoother for polymeric matrices incorporated with arnica extracts recovered at the highest MHG irradiation powers or at the highest set point temperatures of AH treatments.

Fruits from Central Italy: A Chemometric Approach

Nowadays, there is a growing interest in botanicals for human nutrition and care. Arbutus unedo wild berries are edible and medicinal fruits that contain many healthy bioactive components, which can be considered a valuable resource for the food ingredient market and for nutraceutical and cosmetic sectors. In the present study, the polyphenols and in vitro antiradical and hypoglycemic activities of five wild Italian accessions of A. unedo were investigated, and their chemical profiles were treated by means of unsupervised chemometric techniques like the hierarchical and principal component analysis. Moreover, Fourier-transformed mid-infrared spectroscopy was used to provide a rapid assessment of the phytochemical composition of different accessions. Samples differed mainly in their anthocyanin content and overall nutraceutical potential. Anthocyanins were present mainly as glycosides of cyanidin and delphinidin, with delphinidin-3-O-glucoside being the most abundant one, ranging from 49 ± 1 to 111 ± 3 mg g^-1 (for P1 and P2, respectively; p < 0.05). Extracts were screened for their in vitro biological activities by using the 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS^•+), 2,2-diphenyl-1-picrylhydrazyl (DPPH^•) antiradical tests, while their hypoglycemic activity was investigated by the α-glucosidase inhibition test. In both in vitro antiradical tests, the highest capacity was recorded for P2 (EC₅₀: 1.17 and 0.064 mg mL^-1, for DPPH^• and ABTS^•+, respectively), with values higher than those reported in the literature for A. unedo fruit extracts. P2 also showed the highest inhibition power towards α-glucosidase (about 70%). Moreover, the nonparametric correlation analysis pointed out a very high significant correlation between the percentage of α-glucosidase inhibition and cyanidin-3-O-rutinoside (r: 0.973; p < 0.01). Finally, the application of hierarchical analysis to samples analyzed provided three different clusters based on the average phytochemical content coded as low, medium and high. Moreover, principal component analysis made it possible to establish similarities among the accessions depending on their overall nutraceutical characteristics and on the relative anthocyanin content.

Antioxidants and Health-Beneficial Nutrients in Fruits of Eighteen Cucurbita Cultivars: Analysis of Diversity and Dietary Implications

Aging is accompanied by gradual accumulation of molecular damage within cells in response to oxidative stress resulting from adverse environmental factors, inappropriate lifestyle, and numerous diseases. Adequate antioxidant intake is a key factor of proper diet. The study aimed to assess the antioxidant/antiradical capacities of Cucurbita fruits (18 cultivars of the species: C. maxima Duch., C. moschata Duch., C. pepo L., and C. ficifolia Bouché) grown in central Europe. The analyses were based on the FRAP (ferric reducing antioxidant power), CUPRAC (cupric ion reducing antioxidant capacity), and DPPH (2,2-diphenyl-1-picrylhydrazyl radical) assays. The content of phenolic compounds and β-carotene was evaluated with HPLC (high performance liquid chromatography), while the main macro- and micronutrients by ICP-OES (inductively coupled plasma mass spectrometry). The results revealed high intraspecies variability within the Cucurbita genus. The Japanese 'Kogigu' fruits were distinguished as extraordinary sources of phenolic compounds, including syringic and protocatechuic acids, catechin, and kaempferol. Another popular cultivar 'Hokkaido' exhibited the highest antioxidant and antiradical capacities. Most of the fruits proved to be rich sources of zinc and copper. The obtained data are discussed in the context of optimized nutrition of the elderly and suggest that Cucurbita fruits should become daily components of their diet.

Chemo-Diversity and Antiradical Potential of Twelve Matricaria chamomilla L. Populations from Iran: Proof of Ecological Effects

Matricaria chamomilla L. is a popular medicinal herb that is used for healing various diseases and is widely distributed worldwide in temperate climate zones, and even in the subtropical climate of Southern and Western Iran. This study was aimed at comparing the volatile oil constituents, along with antiradical potential and HPLC analysis of methanolic extracts from twelve plant samples growing in Iran. The present research was carried out for the first time on these populations. Among seventeen identified volatile chemicals evaluated by GC/MS and GC/FID, representing 92.73–97.71% of the total oils, α-bisabolone oxide A (45.64–65.41%) was the major constituent, except in case of “Sarableh” as a new chemotype, where (E)- and (Z)-γ-bisabolene (42.76 and 40.08%, respectively) were the predominant components. Oxygenated sesquiterpenes (53.31–74.52%) were the most abundant compounds in the samples excluding “Sarableh” with 91.3% sesquiterpene hydrocarbons. “Sarableh” also exerted the most potent antioxidant capacity with EC₅₀ = 7.76 ± 0.3 µg/mL and 6.51 ± 0.63 mmol TE (Trolox^® equivalents)/g. In addition, populations “Lali” and “Bagh Malek” contained the highest amounts of apigenin and luteolin with 1.19 ± 0.01 mg/g and 2.20 ± 0.0 mg/g of plant material, respectively. Our findings depict a clear correlation between phytochemical profiles and antiradical potential of M. chamomilla and geographical factors.

A Comparative Study of Essential Oil Constituents and Phenolic Compounds of Arabian Lilac (Vitex Trifolia var. Purpurea): An Evidence of Season Effects

To evaluate the fluctuation of secondary metabolites in Arabian lilac during a year, aerial parts of the plant were harvested in the middle of each month. The essential oils content from fresh and dried plant materials was analyzed by gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometer (GC-MS), individually. Phytochemical contents, along with antiradical scavenging potential of the related methanol extracts were separately assessed. The spring and autumn samples (fresh and dried) yielded more essential oil than the other samples. Forty-one compounds were identified totally in the oils and the major constituents characterized were β-caryophyllene, sabinene, and caryophyllene oxide. The extracts obtained from winter and summer plants possessed the highest total phenolics. The maximum amount of total flavonoid content was measured in winter (December and January), whereas the minimum one was observed in spring (March). The summer and winter samples showed the highest and lowest content of flavones and flavanols, respectively, whereas the anthocyanin content was higher in winter than in summer. Moreover, antiradical activity of the extracts in summer and winter samples was higher than in other seasons. Overall, this study can provide useful information regarding the best harvest period of Arabian lilac to yield the desired compounds for application in phytopharmaceutical and food industries.

Ommochromes in invertebrates: biochemistry and cell biology

Ommochromes are widely occurring coloured molecules of invertebrates, arising from tryptophan catabolism through the so-called Tryptophan → Ommochrome pathway. They are mainly known to mediate compound eye vision, as well as reversible and irreversible colour patterning. Ommochromes might also be involved in cell homeostasis by detoxifying free tryptophan and buffering oxidative stress. These biological functions are directly linked to their unique chromophore, the phenoxazine/phenothiazine system. The most recent reviews on ommochrome biochemistry were published more than 30 years ago, since when new results on the enzymes of the ommochrome pathway, on ommochrome photochemistry as well as on their antiradical capacities have been obtained. Ommochromasomes are the organelles where ommochromes are synthesised and stored. Hence, they play an important role in mediating ommochrome functions. Ommochromasomes are part of the lysosome-related organelles (LROs) family, which includes other pigmented organelles such as vertebrate melanosomes. Ommochromasomes are unique because they are the only LRO for which a recycling process during reversible colour change has been described. Herein, we provide an update on ommochrome biochemistry, photoreactivity and antiradical capacities to explain their diversity and behaviour both in vivo and in vitro. We also highlight new biochemical techniques, such as quantum chemistry, metabolomics and crystallography, which could lead to major advances in their chemical and functional characterisation. We then focus on ommochromasome structure and formation by drawing parallels with the well-characterised melanosomes of vertebrates. The biochemical, genetic, cellular and microscopic tools that have been applied to melanosomes should provide important information on the ommochromasome life cycle. We propose LRO-based models for ommochromasome biogenesis and recycling that could be tested in the future. Using the context of insect compound eyes, we finally emphasise the importance of an integrated approach in understanding the biological functions of ommochromes.

Screening of Six Medicinal Plant Extracts Obtained by Two Conventional Methods and Supercritical CO₂ Extraction Targeted on Coumarin Content, 2,2-Diphenyl-1-picrylhydrazyl Radical Scavenging Capacity and Total Phenols Content

Six medicinal plants Helichrysum italicum (Roth) G. Don, Angelica archangelica L., Lavandula officinalis L., Salvia officinalis L., Melilotus officinalis L., and Ruta graveolens L. were used. The aim of the study was to compare their extracts obtained by Soxhlet (hexane) extraction, maceration with ethanol (EtOH), and supercritical CO₂ extraction (SC-CO₂) targeted on coumarin content (by high performance liquid chromatography with ultraviolet detection, HPLC-UV), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging capacity, and total phenols (TPs) content (by Folin–Ciocalteu assay). The highest extraction yields were obtained by EtOH, followed by hexane and SC-CO₂. The highest coumarin content (316.37 mg/100 g) was found in M. officinalis EtOH extracts, but its SC-CO₂ extraction yield was very low for further investigation. Coumarin was also found in SC-CO₂ extracts of S. officinalis, R. graveolens, A. archangelica, and L. officinalis. EtOH extracts of all plants exhibited the highest DPPH scavenging capacity. SC-CO₂ extracts exhibited antiradical capacity similar to hexane extracts, while S. officinalis SC-CO₂ extracts were the most potent (95.7%). EtOH extracts contained the most TPs (up to 132.1 mg gallic acid equivalents (GAE)/g from H. italicum) in comparison to hexane or SC-CO₂ extracts. TPs content was highly correlated to the DPPH scavenging capacity of the extracts. The results indicate that for comprehensive screening of different medicinal plants, various extraction techniques should be used in order to get a better insight into their components content or antiradical capacity.

Colour Evaluation, Bioactive Compound Content, Phenolic Acid Profiles and in Vitro Biological Activity of Passerina del Frusinate White Wines: Influence of Pre-Fermentative Skin Contact Times

Passerina del Frusinate is an autochthonous wine grape variety, which grows in the Lazio region that is currently being evaluated by local wine producers. In this study, colour properties (CIELab coordinates), bioactive compounds (total polyphenols and flavan-3-ols), HPLC-DAD phenolic acid profiles and in vitro biological activity of monovarietal Passerina del Frusinate white wines and the effect of different maceration times (0, 18 and 24 h) were evaluated based on these parameters. Results highlighted statistically significant differences for almost all analysed parameters due to a strong influence of the pre-fermentative skin contact time. The flavan content of macerated wines was six times higher than that of the control, while total polyphenols were 1.5 times higher. According to their phytochemical content, macerated wines showed the highest antiradical capacity tested by means of DPPH(•) and ABTS(+•) assays. Besides, prolonged maceration resulted in a reduction of CIELab coordinates as well as of the content of phenolic substances and antiradical capacity. Among the phenolic acids analysed, the most abundant were vanillic acid and caffeic acid; the latter proved to be the most susceptible to degradation as a result of prolonged maceration. Passerina del Frusinate appears as a phenol-rich white wine with a strong antioxidant potential similar to that of red wines.