Flavonoids in Microheterogeneous Media, Relationship between Their Relative Location and Their Reactivity towards Singlet Oxygen

Comparison of Antioxidant Properties of a Conjugate of Taxifolin with Glyoxylic Acid and Selected Flavonoids

It is known that flavonoids can react with toxic carbonyl compounds in the process of the storage, aging, and digestion of flavonoid-rich foods and beverages. However, the effect of these reactions on the antioxidant properties of the polyphenolic fraction and the properties of the resulting products remain poorly studied. The aim of the present work was to study the antioxidant activity of quercetin, taxifolin, catechin, eriodictyol, hesperetin, naringenin and a product of the condensation of taxifolin with glyoxylic acid, as well as to reveal the structure–activity relationship of these polyphenols. It was found that flavonoids containing the catechol moiety exhibited higher antioxidant activity than hesperetin and naringenin. The product showed the highest hydrogen peroxide scavenging activity, a lower metal-reducing and a higher iron-binding ability than catechol-containing flavonoids, and a lipid peroxidation inhibitory activity comparable with that of taxifolin. Thus, the condensation of flavonoids with toxic carbonyl compounds might lead to the formation of products exhibiting high antioxidant activity. Meanwhile, the conditions under which parent flavonoids and their products exhibit the maximal antioxidant activity may differ. The data suggest that the antioxidant profile of the polyphenolic fraction and bioavailability of polyphenols, carbonyl compounds, and metal ions may change when these reactions occur.

Morin as an imminent functional food ingredient: an update on its enhanced efficacy in the treatment and prevention of metabolic syndromes

Flavonoids represent polyphenolic plant secondary metabolites with a general structure of a 15-carbon skeleton comprising two phenyl rings and a heterocyclic ring. Over 5000 natural flavonoids (flavanones, flavanonols, and flavans) from various plants have been characterized. Several studies provide novel and promising insights into morin hydrate for its different biological activities against a series of metabolic syndromes. The present review is a rendition of its sources, chemistry, functional potency, and protective effects on metabolic syndromes ranging from cancer to brain injury. Most importantly this systematic review article also highlights the mechanisms of interest to morin-mediated management of metabolic disorders. The key mechanisms (anti-oxidative and anti-inflammatory) responsible for its therapeutic potential are well featured after collating the in vitro and in vivo study reports. As a whole, based on the prevailing information rationalizing its medicinal use, morin can be identified as a therapeutic agent for the expansion of human health.

Investigation of Quercetin interaction behaviors with lipid bilayers: Toward understanding its antioxidative effect within biomembrane

Quercetin (QCT), existing in common dietary sources, is an abundant bioflavonoid with planar structure and exerts multiple pharmacological effects. Herein, four kinds of liposomes were prepared as model biomembranes, and then the partition coefficient, distribution in lipid membrane and influence of the QCT on the membrane properties were evaluated. The partition of QCT to lipid membranes was affected by both membrane phase state and the interference of QCT on membrane properties. The location of QCT in lipid membrane was related to the phase state of lipid membrane. In addition, influence of QCT on the compaction of the hydrocarbon tail in lipid membranes was dependent on the unsaturation degree of lipid molecules. Finally, about its antioxidant activity, from the results of 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay, it can be concluded that the interaction of QCT with lipid membrane greatly influences on QCT reductive activity in lipid membrane. Furthermore, mass spectrometry of DOPC molecule showed no lipid oxidation in the presence of QCT, indicating that in addition to the QCT ability toward radical scavenging, the ordering effect of QCT in unsaturated lipid membrane would be helpful to protect lipid membrane from oxidation by inhibiting radical diffusion (synergy effect). Based on lipid membrane analysis, our study made it clear that the effect of QCT on various lipid membrane and its relation with the antioxidant effect of QCT within lipid membrane. Therefore, our analytical method and findings would be also helpful for understanding the mechanism of other antioxidants effects on biomembrane.

A topical formulation containing quercetin-loaded microcapsules protects against oxidative and inflammatory skin alterations triggered by UVB irradiation: enhancement of activity by microencapsulation

Ultraviolet B (UVB) irradiation causes free radical production, increase inflammation and oxidative stress, thus, supporting the use of antioxidants by topical administration as therapeutic approaches. Quercetin (QC) is a flavonoid with antioxidant activity, however, high liposolubility makes it difficult to remain in the viable skin layer. Thus, this study evaluated whether microencapsulation of QC would enhance its activity in comparison with the same dose of free QC (non-active dose) and unloaded-microcapsules added in formulation for topical administration in a mouse model of UVB irradiation targeting the skin. Topical formulation containing Quercetin-loaded microcapsules (TFcQCMC) presents physico-chemical (colour, consistence, phase separation and pH) and functional antioxidant stability at 4 °C, room temperature and 40 °C for 6 months. TFcQCMC inhibited the UVB-triggered depletion of antioxidants observed by GSH (reduced glutathione), ability to reduce iron, ability to scavenge 2,2'-azinobis radical and catalase activity. TFcQCMC also inhibited markers of oxidation (lipid hydroperoxides and superoxide anion production). Concerning inflammation, TFcQCMC reduced the production of inflammatory cytokines, matrix metalloproteinase-9 activity, skin edoema, collagen fibre damage, myeloperoxidase activity/neutrophil recruitment, mast cell and sunburn cell counts. The pharmacological activity of TFcQCMC was not shared by the same pharmaceutical form containing the same dose of free QC or unloaded control microcapsules.

Ellagic acid: A potent glyoxalase-I inhibitor with a unique scaffold

The glyoxalase system, particularly glyoxalase-I (GLO-I), has been approved as a potential target for cancer treatment. In this study, a set of structurally diverse polyphenolic natural compounds were investigated as potential GLO-I inhibitors. Ellagic acid was found, computationally and experimentally, to be the most potent GLO-I inhibitor among the tested compounds which showed an IC50 of 0.71 mmol L-1. Its binding to the GLO-I active site seemed to be mainly driven by ionic interaction via its ionized hydroxyl groups with the central Zn ion and Lys156, along with other numerous hydrogen bonding and hydrophobic interactions. Due to its unique and rigid skeleton, it can be utilized to search for other novel and potent GLO-I inhibitors via computational approaches such as pharmacophore modeling and similarity search methods. Moreover, an inspection of the docked poses of the tested compounds showed that chlorogenic acid and dihydrocaffeic acid could be considered as lead compounds worthy of further optimization.

Nose-to-brain Delivery of Natural Compounds for the Treatment of Central Nervous System Disorders

BACKGROUND

Several natural compounds have demonstrated potential for the treatment of central nervous system disorders such as ischemic cerebrovascular disease, glioblastoma, neuropathic pain, neurodegenerative diseases, multiple sclerosis and migraine. This is due to their well-known antioxidant, anti-inflammatory, neuroprotective, anti-tumor, anti-ischemic and analgesic properties. Nevertheless, many of these molecules have poor aqueous solubility, low bioavailability and extensive gastrointestinal and/or hepatic first-pass metabolism, leading to a quick elimination as well as low serum and tissue concentrations. Thus, the intranasal route emerged as a viable alternative to oral or parenteral administration, by enabling a direct transport into the brain through the olfactory and trigeminal nerves. With this approach, the blood-brain barrier is circumvented and peripheral exposure is reduced, thereby minimizing possible adverse effects.

OBJECTIVE

Herein, brain-targeting strategies for nose-to-brain delivery of natural compounds, including flavonoids, cannabinoids, essential oils and terpenes, will be reviewed and discussed. Brain and plasma pharmacokinetics of these molecules will be analyzed and related to their physicochemical characteristics and formulation properties.

CONCLUSION

Natural compounds constitute relevant alternatives for the treatment of brain diseases but often require loading into nanocarrier systems to reach the central nervous system in sufficient concentrations. Future challenges lie in a deeper characterization of their therapeutic mechanisms and in the development of effective, safe and brain-targeted delivery systems for their intranasal administration.

Carminic Acid Linked to Silica Nanoparticles as Pigment/Antioxidant Bifunctional Excipient for Pharmaceutical Emulsions

The incorporation of pigments and natural polyphenols into inorganic matrices, resulting in a hybrid material that improves the resistance and chemical stability of the pigments and the antioxidant capacity of the materials, has been of great interest to the pharmaceutical, chemical and food industries. The aim of this work was to prepare and characterize a bifunctional pigment-antioxidant nanomaterial-based carminic acid-decorated solid core-mesoporous shell silica nanoparticles, evaluating its properties as a pigment, its antioxidant capacity and its properties as a chemical stabilizer of emulsions. The chemical stability of oil-in-water (O/W) Pickering emulsions was evaluated determining the stability of vitamin E solubilized in the oil phase. Carminic acid was attached through the action of coupling ethylcarbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) agents, and the resulting spherical and homogeneous nanoparticles showed a diameter close to 175 nm. A notorious change of emulsion color was observed by the addition of the nanomaterial. Emulsions showed an attractive pink color, and when the pH was adjusted to pH 3 and pH 9, a change in color was observed, analogous to carminic acid in solution. The nanomaterial incorporation also improved chemical stability, decreasing vitamin E consumption to 9.26% of the initial value, demonstrating an important antioxidant effect of the developed nanomaterial.

Phytoestrogen coumestrol: Antioxidant capacity and its loading in albumin nanoparticles

Coumestrol is a polyphenol with promising therapeutic applications as phytoestrogen, antioxidant and potential cancer chemoprevention agent. The presence of two hydroxyl groups on its chemical structure, with orientation analogous to estradiol, is responsible of both, its antioxidant capacity and its estrogenic activity. However, several studies show that the interaction of polyphenols with food and plasma proteins reduces their antioxidant efficacy. We studied the interaction of coumestrol with bovine serum albumin protein (BSA) by fluorescence spectroscopy and circular dichroism techniques, and the effect of this interaction on its antioxidant activity as a hydroxyl radical scavenger. In addition, coumestrol antioxidant capacity profile using different assays (DPPH, ORAC-FL and ORAC-EPR) was studied. To explain its reactivity we used several methodologies, including DFT calculations, to define its antioxidant mechanism. Coumestrol antioxidant activity unveiled interesting antioxidant properties. BSA interaction with coumestrol reduces significantly photolytic degradation in several media thus preserving its antioxidant properties. Results suggest no significant changes in BSA structure and activity when interacting with coumestrol. Furthermore, this interaction is stronger than for other phytoestrogens such as daidzein and genistein. Considering our promising results, we reported for the first time the fabrication and characterization of coumestrol-loaded albumin nanoparticles. The resulting spherical and homogeneous nanoparticles showed a diameter close to 96 nm. The coumestrol incorporation efficiency in BSA NPs was 22.4%, which is equivalent to 3 molecules of coumestrol for every 10 molecules of BSA.

Theoretical study on the photooxygenation and photorearrangement reactions of 3-hydroxyflavone

The mechanisms of three photodegradation reactions of 3-hydroxyflavone – its photosensitized oxygenation, photooxygenation with ³O₂ and photorearrangement into an indanedione derivative – have been investigated by computing the free energy profiles.

Potential use of nanocarriers with pentacyclic triterpenes in cancer treatments

Ursolic, oleanolic and betulinic acids are representative pentacyclic triterpenoids found in various plants and fruits. Despite having marked antitumor potentials, the very poor water solubility of these triterpenes hinders treatment development. Nanotechnology can enhance solubility, stability, bioavailability and phytochemical delivery, improving the therapeutic efficiency of triterpenes. This review focuses on the formulation, characterization and in vitro/in vivo evaluation of several delivery nanosystems used to enhance the physicochemical properties of ursolic, oleanolic and betulinic acids.

Morin Flavonoid Adsorbed on Mesoporous Silica, a Novel Antioxidant Nanomaterial

Morin (2´,3, 4´,5,7-pentahydroxyflavone) is a flavonoid with several beneficial health effects. However, its poor water solubility and it sensitivity to several environmental factors avoid its use in applications like pharmaceutical and cosmetic. In this work, we synthetized morin-modified mesoporous silica nanoparticles (AMSNPs-MOR) as useful material to be used as potential nanoantioxidant. To achieve this, we characterized its adsorption kinetics, isotherm and the antioxidant capacity as hydroxyl radical (HO•) scavenger and singlet oxygen (1O2) quencher. The experimental data could be well fitted with Langmuir, Freundlich and Temkin isotherm models, besides the pseudo-second order kinetics model. The total quenching rate constant obtained for singlet oxygen deactivation by AMSNPs-MOR was one order of magnitude lower than the morin rate constant reported previously in neat solvents and lipid membranes. The AMSNPs-MOR have good antioxidant properties by itself and exhibit a synergic effect with morin on the antioxidant property against hydroxyl radical. This effect, in the range of concentrations studied, was increased when the amount of morin adsorbed increased.