Abstract Objective Quercetin, a commonly occurring flavonoid and well known antioxidant, has been suggested to possess other beneficial activities. The present study investigated the possible ...anti-inflammatory effects of physiologically attainable quercetin concentrations. Methods The effects of quercetin were tested in vitro, i.e., added to blood in the test tube, and ex vivo and in vivo, i.e., in blood taken after 4 wk of administration of quercetin in an intervention study. Results Quercetin dose-dependently inhibited in vitro lipopolysaccharide-induced tumor necrosis factor-α production in the blood of healthy volunteers. At a concentration of 1 μM, quercetin caused a 23% reduction. The in vitro lipopolysaccharide-induced interleukin-10 production remained unaffected by quercetin. A 4-wk quercetin intervention resulted in a significant increase in plasma quercetin concentration. The supplementation also increased total plasma antioxidant status but did not affect glutathione, vitamin C, and uric acid plasma concentrations. Basal and ex vivo lipopolysaccharide-induced tumor necrosis factor-α levels were not altered by the intervention. Conclusion The present study shows that quercetin increases antioxidant capacity in vivo and displays anti-inflammatory effects in vitro, but not in vivo or ex vivo, in the blood of healthy volunteers. This lack of effect is probably due to their low cytokine and high antioxidant levels at baseline, indicating that neither inflammation nor oxidative stress is present. Only in people with increased levels of inflammation and oxidative stress, e.g., patients with a disease of which the pathology is associated with these two processes, might antioxidant supplementation be fruitful.
The contemporary pathophysiological model of non-alcoholic fatty liver disease (NAFLD) comprises multiple parallel pathways with a dynamic cross talk that cumulate in steatosis and inflammation, and ...ultimately fibrosis, cirrhosis, liver failure, and hepatocellular carcinoma. So far, no pharmacological treatment has been approved. A major impediment of drugs, in general, is that they are intended to act on one single target in the pathology of a disease. However, the multitude of pathways involved in the pathogenesis of NAFLD underpins the need for treatments that address these various pathways. Interestingly, flavonoids have been found to have positive effects on lipid metabolism, insulin resistance, inflammation, and oxidative stress, the most important pathophysiological pathways in NAFLD. This puts flavonoids in the spotlight for the treatment of NAFLD and prompted us to review the existing evidence for the use of these food-derived compounds in the treatment of NAFLD.
Quercetin, a member of the flavonoids family, is one of the most prominent dietary antioxidants. It is ubiquitously present in foods including vegetables, fruit, tea and wine as well as countless ...food supplements and is claimed to exert beneficial health effects. This includes protection against various diseases such as osteoporosis, certain forms of cancer, pulmonary and cardiovascular diseases but also against aging. Especially the ability of quercetin to scavenge highly reactive species such as peroxynitrite and the hydroxyl radical is suggested to be involved in these possible beneficial health effects. Consequently, numerous studies have been performed to gather scientific evidence for these beneficial health claims as well as data regarding the exact mechanism of action and possible toxicological aspects of this flavonoid. The purpose of this review is to evaluate these studies in order to elucidate the possible health-beneficial effects of the antioxidant quercetin. Firstly, the definitions as well as the most important aspects regarding free radicals, antioxidants and oxidative stress will be discussed as background information. Subsequently, the mechanism by which quercetin may operate as an antioxidant (tested in vitro) as well as the potential use of this antioxidant as a nutraceutical (tested both ex vivo and in vivo) will be discussed.
Life on Earth has to adapt to the ever changing environment. For example, due to introduction of oxygen in the atmosphere, an antioxidant network evolved to cope with the exposure to oxygen. The ...adaptive mechanisms of the antioxidant network, specifically the glutathione (GSH) system, are reviewed with a special focus on the time. The quickest adaptive response to oxidative stress is direct enzyme modification, increasing the GSH levels or activating the GSH-dependent protective enzymes. After several hours, a hormetic response is seen at the transcriptional level by up-regulating Nrf2-mediated expression of enzymes involved in GSH synthesis. In the long run, adaptations occur at the epigenetic and genomic level; for example, the ability to synthesize GSH by phototrophic bacteria. Apparently, in an adaptive hormetic response not only the dose or the compound, but also time, should be considered. This is essential for targeted interventions aimed to prevent diseases by successfully coping with changes in the environment e.g., oxidative stress.
Ten misconceptions about antioxidants Bast, Aalt; Haenen, Guido R.M.M
Trends in pharmacological sciences (Regular ed.),
08/2013, Letnik:
34, Številka:
8
Journal Article
Recenzirano
Highlights • Opinions on antioxidants are highly polarized, leading to misunderstanding in the field. • Specific antioxidants may have specific effects and side effects. • With their pleiotropic ...modes of action, antioxidants should be considered bioactives.
'Forever' chemicals that unintendedly in the long run pollute the environment, climate change, COVID; life continuously faces all sorts of unforeseen challenges that are an inevitable side product of ...'progress' ....
Grain is an important source of phytochemicals, which have potent antioxidant capacity. They have been implicated in the beneficial health effect of whole grains in reducing cardiovascular disease ...and type 2 diabetes. The aim of the present study was to identify the most important antioxidant fractions of wheat grain. It was found that the aleurone content of these fractions was highly correlated with the antioxidant capacity of the fractions (r = 0.96, p < 0.0001). Ferulic acid appeared to be the major contributor to the antioxidant capacity in fractions with higher antioxidant capacity. The contribution of protein was rather limited. It was concluded that the antioxidant potency of wheat grain fractions is predominantly determined by aleurone content, which can be attributed to the presence of relatively large amounts of phenolic compounds, primarily ferulic acid.
Summary Background & aims Oxidative stress and low antioxidant levels are implicated in the aetiology of sarcoidosis, an inflammatory disease. Quercetin is a potent dietary antioxidant that also ...displays anti-inflammatory activities. Consequently, the aim is to examine the effect of quercetin supplementation on markers of oxidative stress and inflammation in sarcoidosis. Methods A double-blind intervention study has been conducted with two groups of non-smoking, un-treated sarcoidosis patients, matched for age and gender. One group was given 4x500 mg quercetin ( n = 12) orally within 24 h, the other one placebo ( n = 6). Plasma malondialdehyde levels were used as marker of oxidative damage, plasma ratios of TNFα/IL-10 and IL-8/IL-10 as pro-inflammatory markers. Results Quercetin supplementation improved the antioxidant defence, indicated by the increased total plasma antioxidant capacity. Moreover, quercetin supplementation also reduced markers of oxidative stress and inflammation in the blood of sarcoidosis patients. The effects of quercetin supplementation appeared to be more pronounced when the levels of the oxidative stress and inflammation markers were higher at baseline. Conclusions Sarcoidosis patients might benefit from the use of antioxidants, such as quercetin, to reduce the occurring oxidative stress as well as inflammation. The effects of long-term use of antioxidant supplementation in sarcoidosis, using e.g. quercetin, on improvement of lung function remain to be investigated. ( www.clinicaltrials.gov ; NCT-00402623).
Accumulating evidence suggests that foods rich in flavanols decrease the risk of developing cardiovascular diseases. Attenuation of oxidative stress was suggested to contribute to the cardiovascular ...benefit of flavanols. Up to now it was unclear whether flavanol metabolites can also protect cells from oxidative stress. The aim of the present study was to determine the potential contribution of several glucuronidated, methylated and sulfated metabolites of (-)-epicatechin (EC) and (+)-catechin (Cat) to the protection of human vascular endothelial cells (HUVECs) against oxidative stress.
The relative potency of the tested compounds to scavenge superoxide anion radicals showed that a free catechol moiety in the molecule is important for the direct antioxidant activity. EC and Cat (0.5, 1, 10µM) were potent radical scavengers and provided protection against intracellular oxidative stress induced by hydrogen peroxide. Although the metabolites provided less intracellular protection compared to EC and Cat, the tested methylated and glucuronidated metabolites reduced oxidative stress significantly in HUVECs.
Our results indicate that the metabolites have a relevant contribution in the intracellular protection of EC and Cat against oxidative stress. Also, the direct antioxidant activity plays an important role in this protection.
We experimentally demonstrate single-pulse all-optical switching in Pt/Co/Gd stacks using linearly polarized laser pulses. This shows that thermal single-pulse switching is not limited to ...ferrimagnetic alloys, but is also possible in ferrimagnetic multilayers that are highly suitable for future applications due to easy fabrication and (interface) engineering. Moreover, it is shown that the threshold fluence needed for the optical switch strongly depends on the thickness of the Co layer, with a remarkable low threshold fluence of ≈1.2 mJ/cm2 for a Co thickness of 0.8 nm. Lastly, helicity-dependent measurements showed no significant effect of the magnetic circular dichroism in these thin magnetic layers.
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