ascorbic-acid and 3-4-dihydroxyphenylethanol

Over the last years, different nanomaterials have been investigated to design highly selective and sensitive sensors, reaching nano/picomolar concentrations of biomolecules, which is crucial for medical sciences and the healthcare industry in order to assess physiological and metabolic parameters. The discovery of graphene (G) has unexpectedly impulsed research on developing cost-effective electrode materials owed to its unique physical and chemical properties, including high specific surface area, elevated carrier mobility, exceptional electrical and thermal conductivity, strong stiffness and strength combined with flexibility and optical transparency. G and its derivatives, including graphene oxide (GO) and reduced graphene oxide (rGO), are becoming an important class of nanomaterials in the area of optical and electrochemical sensors. The presence of oxygenated functional groups makes GO nanosheets amphiphilic, facilitating chemical functionalization. G-based nanomaterials can be easily combined with different types of inorganic nanoparticles, including metals and metal oxides, quantum dots, organic polymers, and biomolecules, to yield a wide range of nanocomposites with enhanced sensitivity for sensor applications. This review provides an overview of recent research on G-based nanocomposites for the detection of bioactive compounds, providing insights on the unique advantages offered by G and its derivatives. Their synthesis process, functionalization routes, and main properties are summarized, and the main challenges are also discussed. The antioxidants selected for this review are melatonin, gallic acid, tannic acid, resveratrol, oleuropein, hydroxytyrosol, tocopherol, ascorbic acid, and curcumin. They were chosen owed to their beneficial properties for human health, including antibiotic, antiviral, cardiovascular protector, anticancer, anti-inflammatory, cytoprotective, neuroprotective, antiageing, antidegenerative, and antiallergic capacity. The sensitivity and selectivity of G-based electrochemical and fluorescent sensors are also examined. Finally, the future outlook for the development of G-based sensors for this type of biocompounds is outlined.

Topics: Antioxidants; Ascorbic Acid; Biosensing Techniques; Curcumin; Electric Conductivity; Electrodes; Free Radicals; Gallic Acid; Graphite; Humans; Iridoid Glucosides; Melatonin; Metals; Nanocomposites; Nanostructures; Oxides; Phenylethyl Alcohol; Quantum Dots; Resveratrol; Tannins; Tocopherols

Liver ischemia-reperfusion injury (IRI) is a phenomenon inherent to hepatic surgery that severely compromises the organ functionality, whose underlying mechanisms involve cellular and molecular interrelated processes leading to the development of an excessive inflammatory response. Liver resident cells and those recruited in response to injury generate pro-inflammatory signals such as reactive oxygen species, cytokines, chemokines, proteases and lipid mediators that contribute to hepatocellular necrosis and apoptosis. Besides, dying hepatocytes release damage-associated molecular patterns that actívate inflammasomes to further stimulate inflammatory responses leading to massive cell death. Since liver IRI is a complication of hepatic surgery in man, extensive preclinical studies have assessed potential protective strategies, including the supplementation with natural compounds, with the objective to downregulate nuclear factor-κB functioning, the main effector of inflammatory responses. This can be accomplished by either the activation of peroxisome proliferator-activated receptor-α, G protein-coupled receptor 120 or antioxidant signaling pathways, the synthesis of specific pro-resolving mediators, downregulation of Toll-like receptor 4 activity or additional contributory mechanisms that are beginning to be understood. The latter aspect is a crucial issue to be accomplished in preclinical studies, in order to establish adequate conditions for the supplementation with natural products before major liver surgeries in man involving warm IR, such as hepatic trauma or resection of large intrahepatic tumors.

Topics: Animals; Ascorbic Acid; Biological Products; Fatty Acids, Unsaturated; Humans; Liver; Phenylethyl Alcohol; Reperfusion Injury; Vitamin E; Vitamins

Hydroxytyrosol (HT) is a main phenolic component of olive oil. In this study, we investigated the safety and effects produced by HT purified (99.5%) from olive mill waste. HT was administered at a daily dosage of 45mg for 8 weeks to volunteers with mild hyperlipidemia (n=14). We measured markers of cardiovascular disease risk, enzyme markers of several clinical conditions, hematology, antioxidant parameters, vitamins and minerals at baseline (T0), 4 weeks (T4) and 8 weeks (T8). The values obtained at T4 and T8 were compared with baseline. We found that the HT dose administered was safe and mostly did not influence markers of cardiovascular disease, blood lipids, inflammatory markers, liver or kidney functions and the electrolyte balance. Serum iron levels remained constant but a significant (P<0.05) decrease in ferritin at T4 and T8 was found. Serum folate and red blood cell folate levels were also reduced at T4 and T8. Finally, vitamin C increased by two-fold at T4 and T8 compared with levels at baseline. These results indicate a physiologically relevant antioxidant function for HT through increasing endogenous vitamin C levels.

Topics: Adult; Ascorbic Acid; Blood Pressure; Body Mass Index; Dietary Supplements; Female; Folic Acid; Healthy Volunteers; Humans; Iron; Kidney Function Tests; Lipid Metabolism; Lipids; Liver Function Tests; Male; Olive Oil; Phenylethyl Alcohol

Nitric oxide (NO) dysfunction, oxidative stress, and dyslipidemia are main risk factors associated with the pathophysiology of diabetic complications. In this study, 3,4-dihydroxyphenethyl nitrate (HT-ONO

Topics: Administration, Oral; Animals; Antioxidants; Diabetes Mellitus, Experimental; Hypoglycemic Agents; Hypolipidemic Agents; Mice; Molecular Structure; Nitrates; Nitric Oxide; Phenylethyl Alcohol; Streptozocin

The natural antioxidant hydroxytyrosol (HT) was used to functionalize a strawberry puree. The effect of the antioxidant on the stability of the two bioactive forms of vitamin C (ascorbic acid-AA and dehydroascorbic acid-DHAA) in strawberry puree stored at 4 °C, compared with the effect on a model system of AA in water, was investigated. In the absence of HT, the concentration of vitamin C in strawberry puree decreased but not in the model system. Low concentrations of HT in strawberry puree (0.05 and 0.1 mg HT/g puree) stabilized vitamin C and improved its antioxidant activity. However, at high concentrations of HT (from 0.5 mg HT/g puree), although the antioxidant activity improved, degradation of vitamin C occurred. Therefore, the concentration of HT used to obtain a functionalized strawberry puree it is very important. An adequate concentration increases the antioxidant activity and protects vitamin C from degradation, developing a functional food. However, an inadequate concentration of HT affects the vitamin C content, which is essential for the human diet because it cannot be biosynthetized by the organism.

Topics: Antioxidants; Ascorbic Acid; Biological Products; Chromatography, High Pressure Liquid; Drug Stability; Fragaria; Molecular Structure; Oxidation-Reduction; Phenylethyl Alcohol; Solutions; Temperature

Parkinson disease (PD) features profound striatal dopamine depletion and Lewy bodies containing abundant precipitated alpha-synuclein. Mechanisms linking alpha-synucleinopathy with the death of dopamine neurons remain incompletely understood. One such link may be 3,4-dihydroxyphenylacetaldehyde (DOPAL). All of the intra-neuronal metabolism of dopamine passes through DOPAL, which is toxic. DOPAL also potently oligomerizes alpha-synuclein and alpha-synuclein oligomers are thought to be pathogenic in PD. Another implicated factor in PD pathogenesis is metal ions, and alpha-synuclein contains binding sites for these ions. In this study we tested whether divalent metal ions augment DOPAL-induced oligomerization of alpha-synuclein in cell-free system and in PC12 cells conditionally over-expressing alpha-synuclein. Incubation with divalent metal ions augmented DOPAL-induced oligomerization of alpha-synuclein (Cu(2+)>Fe(2+)>Mn(2+)), whereas monovalent Cu(1+) and trivalent Fe(3+) were without effect. Other dopamine metabolites, dopamine itself, and metal ions alone or in combination with dopamine, also had no effect. Antioxidant treatment with ascorbic acid and divalent cation chelation with EDTA attenuated the augmentation by Cu(2+) of DOPAL-induced alpha-synuclein oligomerization. Incubation of PC12 cells with L-DOPA markedly increased intracellular DOPAL content and promoted alpha-synuclein dimerization. Co-incubation with Cu(2+) amplified (p=0.01), while monoamine oxidase inhibition prevented, L-DOPA-related dimerization of alpha-synuclein (p=0.01). We conclude that divalent metal ions augment DOPAL-induced oligomerization of alpha-synuclein. Drugs that interfere with this interaction might constitute a novel approach for future treatment or prevention approaches.

Topics: 3,4-Dihydroxyphenylacetic Acid; alpha-Synuclein; Animals; Antioxidants; Ascorbic Acid; Cations, Divalent; Chelating Agents; Copper; Dopamine; Edetic Acid; Humans; Iron; Manganese; PC12 Cells; Phenylethyl Alcohol; Protein Aggregates; Protein Multimerization; Rats

Oxidative stress is implicated in the development of a range of neurological diseases. There is increasing interest in the neuroprotective efficacy of antioxidants in modulating such processes with at least one polyphenolic being tested as a prophylactic in Alzheimer's disease. Beneficial effects of adjunctive n-3 polyunsaturated fatty acids with combined intakes of vitamin C and E on both the positive and negative symptoms of schizophrenia have been reported. Robust in vitro systems are desirable, enabling a mechanistic investigation of the molecular mechanisms underpinning such effects and identification of further potentially efficacious nutraceuticals.. A comparative study employing a human lymphoblastoid cell line derived from a subject with early onset schizophrenia, a neuroblastoma IMR-32 cell line and the histiocytic lymphoma U937 cell line was undertaken. The cytoprotective effects of two phenols in affording protection to cellular DNA from an oxidative challenge were assessed in untreated and fatty acid treated cell lines.. Marked differences in the uptake of fatty acids by the cell types were found and the IMR-32 cell line was most susceptible to the oxidant challenge. Hydroxytyrosol gave significant cytoprotection in all three-cell lines and this possible neuroprotective efficacy warrants further investigation, both in vitro and in vivo.

Topics: Antioxidants; Ascorbic Acid; Cell Line, Tumor; Cytoprotection; DNA Damage; Fatty Acids, Essential; Fatty Acids, Unsaturated; Humans; Hydrogen Peroxide; Monocytes; Neurons; Oxidants; Oxidative Stress; Phenols; Phenylethyl Alcohol; Vitamin E

Antioxidants minimize oxidation of the lipid components in foods. There is an increasing interest in the use of natural and/or synthetic antioxidants in food preservation, but it is important to evaluate such compounds fully for both antioxidant and pro-oxidant properties. The properties of thymol, carvacrol, 6-ginerol, hydroxytyrosol and zingerone were characterized in detail. Thymol, carvacrol, 6-gingerol and hydroxytyrosol decreased peroxidation of phospholipid liposomes in the presence of iron(III) and ascorbate, but zingerone had only a weak inhibitory effect on the system. The compounds were good scavengers of peroxyl radicals (CCl3O2; calculated rate constants > 10(6) M-1 sec-1) generated by pulse radiolysis. Thymol, carvacrol, 6-gingerol and zingerone were not able to accelerate DNA damage in the bleomycin-Fe(III) system. Hydroxytyrosol promoted deoxyribose damage in the deoxyribose assay and also promoted DNA damage in the bleomycin-Fe(III) system. This promotion was inhibited strongly in the deoxyribose assay by the addition of bovine serum albumin to the reaction mixtures. Our data suggest that thymol, carvacrol and 6-gingerol possess useful antioxidant properties and may become important in the search for 'natural' replacements for 'synthetic' antioxidant food additives.

Topics: Antioxidants; Ascorbic Acid; Bleomycin; Catechols; Cymenes; Deoxyribose; DNA Damage; Fatty Alcohols; Ferric Compounds; Food Preservation; Guaiacol; Hydroxyl Radical; Lipid Peroxidation; Liposomes; Monoterpenes; Phenylethyl Alcohol; Pulse Radiolysis; Terpenes; Thymol