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Lipophilic hydroxytyrosol esters significantly improve the oxidative state of human red blood cells
No full textMitochondria accumulate large amounts of quercetin: prevention of mitochondrial damage and release upon oxidation of the extramitochondrial fraction of the flavonoid
No full textMitochondria accumulate large amounts of quercetin: prevention of mitochondrial damage and release upon oxidation of the extramitochondrial fraction of the flavonoid
Quercetin is a naturally occurring flavonoid producing beneficial effects for the human health, via scavenging of reactive oxygen species/metal chelation and stimulation/inhibition of enzyme activities/signal transduction pathways. While the hierarchy and relevance of these effects is not yet fully appreciated, it appears obvious that its accumulation in specific subcellular compartments might dictate the specificity of the effects mediated by the flavonoid. Quercetin uptake in Jurkat cells is extremely rapid and associated with a remarkable accumulation of the flavonoid, dependent on its binding to intracellular components. Cell-associated quercetin is biologically active, quantitatively consumed to promote survival in the presence of reactive species, such as peroxynitrite (ONOO−), or reduction of extracellular oxidants via activation of plasma membrane oxidoreductases. In alternative, quercetin is very slowly released upon post-incubation in drug-free medium, an event significantly accelerated by extracellular albumin. Quercetin uptake is also observed in isolated mitochondria, resulting in an enormous accumulation of the flavonoid, consumed under conditions associated with prevention of lipid peroxidation induced by ONOO−. Interestingly, remarkable quercetin accumulation is also detected in the mitochondria isolated from quercetin-pre-loaded cells, and exposure to either ONOO− or extracellular oxidants caused the parallel loss of both the mitochondrial and cytosolic fractions of the flavonoid. In conclusion, Jurkat cells accumulate large amounts of quercetin and even larger amounts of the flavonoid further accumulate in their mitochondria. Intramitochondrial quercetin appears to be functional for prevention of mitochondrial damage as well as for redistribution to the cytosol, when the fraction of the flavonoid therein retained is progressively consumed either by cell-permeant oxidants or by activation of plasma membrane oxidoreductases, thereby implying that mitochondria represent a reservoir of biologically active quercetin
Honey flavonoids as protection agents against oxidative damage to human red blood cells
No full textHoney flavonoids as protection agents against oxidative damage to human red blood cells
Abstract
Unlike other components of the Mediterranean diet, namely fruits, vegetables, wine and olive oil, that have been intensively studied for the ability to protect vital cell components from oxidative damage and slow the aging process by neutralizing free radicals, honey is relatively unknown for its
antioxidant properties. Among natural food antioxidants, polyphenols are ubiquitously distributed in the vegetable kingdom as plant secondary metabolites. Natural polyphenols can range from simple molecules to highly polymerised compounds, with flavonoids representing the most common and widely distributed subgroup. The aim of our work was to assess and compare antioxidant activities of honey phenol extracts, separated by their hydrophobicity. Available literature indicates that no previous studies have been reported on antioxidant properties of polyphenols of italian honeys. Thus, to our knowledge, this is the first report of such an in vitro study. In the present study, raw multifloral honey, collected over the Marche region (central Italy), was used. Phenols were absorbed on an Amberlite XAD-2 column and eluted by methanol. The eluate was vacuum-dried, dissolved with water and partitioned in ethyl ether to fractionate the polar
and non-polar compounds. Honey phenol extracts separated on the base of their hydrophobicity were evaluated for the antioxidant content by the FRAP assay, and for the ability to inhibit oxidative damage induced by radical species generated in the water phase or in the membrane of human erythrocytes. The peroxyl radical-scavenger activity was tested by the inhibition of RBC hemolysis induced by 2,20-azobis-(amidinopropane)dihydrochloride (AAPH) which generates such radicals, attacking from the outside of the membrane. The antioxidant efficiency against oxidative stress induced by hydroperoxides was also estimated, utilising water-soluble hydrogen peroxide (H2O2) and the lipophilic tert-butylhydroperoxide (t-BOOH). The water and ether fractions obtained from crude methanol extract of honey exhibited a phenolic content of 5.33 and 2.62 mg caffeic acid equivalents/100 g honey, respectively. These values correlate well with those of total antioxidant power, as assessed by FRAP assay (37.67 vs. 10.65 lmol/100 g honey). Flavonoid contents were 2.57 and 1.64 mg catechin equivalents/100 g honey for ether and water fractions, respectively. Although both honey fractions protect erythrocytes against AAPH -induced lysis, only the ether fraction was found to be active in inhibiting hemolysis but not methemoglobin and ferrylhemoglobin formation caused by H2O2. In addition, the ether fraction prevents t-BOOH -induced lipid peroxidation in whole erythrocytes and in isolated membranes. The significant antioxidant effect against damages induced by both water-soluble and hydrophobic exogenous oxidants suggests that the ether fraction, owing to its lipophilic character, can interact with red blood cell membrane, and the protective effect can be associated with the binding of the flavonoids to the membrane. On the other hand, the water fraction is more hydrophilic than ether fraction and it acts only from the outside of the membrane by scavenging the radicals before they attack the erythrocyte membrane
Raw Millefiori honey is packed full of antioxidants
No full textRaw Millefiori honey is packed full of antioxidants
Abstract
Honey is the natural substance produced by honeybees, Apis mellifera, in almost every country of the world. Raw honeys are usually produced by small farms and left in their natural state without undergoing processing (e.g., filtration and heat treatment). Honey is essentially a concentrated aqueous solution of inverted sugar, but it also contains a very complex mixture of other saccharides, enzymes, amino and organic acids, polyphenols, carotenoid-like substances, Maillard reaction products, vitamins, and minerals. Among minor honey constituents, polyphenols such as flavonoids
and phenolic acids, may function as natural antioxidants in our diet. In recent years, considerable
interest has been focussed on dietary antioxidants in reference to their protective effect against oxidative damage.There are many studies about the polyphenol content and antioxidative effects of fruits, vegetables and beverages; in contrast, hardly any work has been reported with honey. Available literature indicates that no previous antioxidant power studies have been done on Italian honeys; thus, the objective of this work was to evaluate antioxidant activity of two representative Italian raw honeys, , i.e., Millefiori and Acacia, obtained from beekeepers belonging to the same geographical region (central Italy) as a function of their sensorial characteristics and content of total polyphenols and flavonoids. Total polyphenols, flavonoids and antioxidant power of samples from Millefiori and Acacia raw honey varieties were evaluated. Phenolic content, expressed as caffeic acid equivalents, ranged from 12.5 to 17.5 mg/100 g and from 3 to 11 mg/100 g in Millefiori and Acacia honeys, respectively. All Millefiori samples exhibited the highest flavonoid concentration being between 1.23 and 2.93 mg catechin equivalents (CE)/100 g honey. Total flavonoids in 100 g Acacia honeys were in the range of 0.45–1.01 mg CE. Acacia honeys had lower total antioxidant power, as assessed by ferric reducing/antioxidant power assay, than Millefiori. The relationship between phenolic content and antioxidant power was discussed. These results demonstrated a strong correlation between honey colour and antioxidant power, with darker and more crystallized honeys having stronger antioxidant activity than lighter and transparent honeys.. Comparative experimental analysis was performed with an artificial honey and processed honeys. Raw Millefiori honey is rich in both amount and variety of antioxidant substances, and its inclusion in the diet may be recommended to complement other polyphenol sources
Il miele come fonte di antiossidanti naturali
No full textConvegno: Sicurezza e qualità alimentare per la promozione della salut
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