Flavonoids as Antioxidants
TL;DR: The capacity of flavonoids to act as antioxidants in vitro has been the subject of several studies in the past years, and important structure-activity relationships of the antioxidant activity have been established as mentioned in this paper.
Abstract: Flavonoids are phenolic substances isolated from a wide range of vascular plants, with over 8000 individual compounds known. They act in plants as antioxidants, antimicrobials, photoreceptors, visual attractors, feeding repellants, and for light screening. Many studies have suggested that flavonoids exhibit biological activities, including antiallergenic, antiviral, antiinflammatory, and vasodilating actions. However, most interest has been devoted to the antioxidant activity of flavonoids, which is due to their ability to reduce free radical formation and to scavenge free radicals. The capacity of flavonoids to act as antioxidants in vitro has been the subject of several studies in the past years, and important structure-activity relationships of the antioxidant activity have been established. The antioxidant efficacy of flavonoids in vivo is less documented, presumably because of the limited knowledge on their uptake in humans. Most ingested flavonoids are extensively degraded to various phenolic acids, some of which still possess a radical-scavenging ability. Both the absorbed flavonoids and their metabolites may display an in vivo antioxidant activity, which is evidenced experimentally by the increase of the plasma antioxidant status, the sparing effect on vitamin E of erythrocyte membranes and low-density lipoproteins, and the preservation of erythrocyte membrane polyunsaturated fatty acids. This review presents the current knowledge on structural aspects and in vitro antioxidant capacity of most common flavonoids as well as in vivo antioxidant activity and effects on endogenous antioxidants.
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TL;DR: Phenolic compounds, ubiquitous in plants are an essential part of the human diet, and are of considerable interest due to their antioxidant properties as mentioned in this paper, and their structures may range from a simple phenolic molecule to a complex high-molecular weight polymer.
2,723 citations
TL;DR: The data demonstrated that processing can have significant effects on ORAC(FL).
Abstract: Both lipophilic and hydrophilic antioxidant capacities were determined using the oxygen radical absorbance capacity (ORACFL) assay with fluorescein as the fluorescent probe and 2,2‘-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator on over 100 different kinds of foods, including fruits, vegetables, nuts, dried fruits, spices, cereals, infant, and other foods. Most of the foods were collected from four different regions and during two different seasons in U.S. markets. Total phenolics of each sample were also measured using the Folin−Ciocalteu reagent. Hydrophilic ORACFL values (H-ORACFL) ranged from 0.87 to 2641 μmol of Trolox equivalents (TE)/g among all of the foods, whereas lipophilic ORACFL values (L-ORACFL) ranged from 0.07 to 1611 μmol of TE/g. Generally, L-ORACFL values were <10% of the H-ORACFL values except for a very few samples. Total antioxidant capacity was calculated by combining L-ORACFL and H-ORACFL. Differences of ORACFL values in fruits and vegetables from different...
1,673 citations
TL;DR: Unraveling the signaling events initiated at the cellular level by oxidative free radicals as well as the physiological responses to such stress is important to better understand disease pathogenesis and to develop new therapies to manage a variety of conditions for which current therapies are not always sufficient.
Abstract: Reactive oxygen species (ROS) are generated as by-products of normal cellular metabolic activities. Superoxide dismutase, glutathione peroxidase, and catalase are the enzymes involved in protecting cells from the damaging effects of ROS. ROS are produced in response to ultraviolet radiation, cigarette smoking, alcohol, nonsteroidal anti-inflammatory drugs, ischemia-reperfusion injury, chronic infections, and inflammatory disorders. Disruption of normal cellular homeostasis by redox signaling may result in cardiovascular, neurodegenerative diseases and cancer. ROS are produced within the gastrointestinal (GI) tract, but their roles in pathophysiology and disease pathogenesis have not been well studied. Despite the protective barrier provided by the mucosa, ingested materials and microbial pathogens can induce oxidative injury and GI inflammatory responses involving the epithelium and immune/inflammatory cells. The pathogenesis of various GI diseases including peptic ulcers, gastrointestinal cancers, and inflammatory bowel disease is in part due to oxidative stress. Unraveling the signaling events initiated at the cellular level by oxidative free radicals as well as the physiological responses to such stress is important to better understand disease pathogenesis and to develop new therapies to manage a variety of conditions for which current therapies are not always sufficient.
1,462 citations
Cites background from "Flavonoids as Antioxidants"
...Plant polyphenols are important antioxidants, and dietary intake of these compounds can be up to 50–800 mg/day (232)....
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TL;DR: The distribution of ka Kempferol in the plant kingdom and its pharmacological properties are reviewed and the pharmacokinetics and safety of kaempferol are analyzed to help understand the health benefits of kaEMPferol-containing plants and to develop this flavonoid as a possible agent for the prevention and treatment of some diseases.
Abstract: Epidemiological studies have revealed that a diet rich in plant-derived foods has a protective effect on human health. Identifying bioactive dietary constituents is an active area of scientific investigation that may lead to new drug discovery. Kaempferol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) is a flavonoid found in many edible plants (e.g. tea, broccoli, cabbage, kale, beans, endive, leek, tomato, strawberries and grapes) and in plants or botanical products commonly used in traditional medicine (e.g. Ginkgo biloba, Tilia spp, Equisetum spp, Moringa oleifera, Sophora japonica and propolis). Some epidemiological studies have found a positive association between the consumption of foods containing kaempferol and a reduced risk of developing several disorders such as cancer and cardiovascular diseases. Numerous preclinical studies have shown that kaempferol and some glycosides of kaempferol have a wide range of pharmacological activities, including antioxidant, anti-inflammatory, antimicrobial, anticancer, cardioprotective, neuroprotective, antidiabetic, anti-osteoporotic, estrogenic/antiestrogenic, anxiolytic, analgesic and antiallergic activities. In this article, the distribution of kaempferol in the plant kingdom and its pharmacological properties are reviewed. The pharmacokinetics (e.g. oral bioavailability, metabolism, plasma levels) and safety of kaempferol are also analyzed. This information may help understand the health benefits of kaempferol-containing plants and may contribute to develop this flavonoid as a possible agent for the prevention and treatment of some diseases.
987 citations
Cites background from "Flavonoids as Antioxidants"
...This phenoxyl radical may either react with a second radical becoming stable (antioxidant effect), or interact with oxygen resulting in the generation of ROS (prooxidant effect) [44]....
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...The antioxidant properties of flavonoids are widely acknowledged [42-44]....
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TL;DR: Analytical techniques for the characterization of juices from different Citrus fruits regarding their flavonoid content (even if present in only trace amounts), concentrating on the most widely used methods (LC-MS and LC-MS-MS).
Abstract: In the early nineties the presence of flavonoids in Citrus juices began to attract the attention of a number of researchers, as a result of their biological and physiological importance. This short review will explore two different aspects. The first part will focus on analytical techniques for the characterization of juices from different Citrus fruits regarding their flavonoid content (even if present in only trace amounts), concentrating on the most widely used methods (LC-MS and LC-MS-MS). The second part analyzes data reported in the literature regarding the composition of Citrus juices. The main components that have been detected so far are flavanone-O-glycosides and flavone-O- or -C-glycosides. The presence of such derivatives in various hand-squeezed and industrial juices is discussed, with special emphasis on their correlation to different species.
584 citations
Cites background from "Flavonoids as Antioxidants"
...Flavonoids show a strong antioxidant and radical scavenging activity [6] and appear to be associated with reduced risk for certain chronic diseases [7], the prevention of some cardiovascular disorders [8] and certain kinds of cancerous processes [9]....
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TL;DR: This review presents the current knowledge on structural aspects and in vitro antioxidant capacity of most common flavonoids as well as in vivo antioxidant activity and effects on endogenous antioxidants.
Abstract: Flavonoids are phenolic substances isolated from a wide range of vascular plants, with over 8000 individual compounds known. They act in plants as antioxidants, antimicrobials, photoreceptors, visual attractors, feeding repellants, and for light screening. Many studies have suggested that flavonoids exhibit biological activities, including antiallergenic, antiviral, antiinflammatory, and vasodilating actions. However, most interest has been devoted to the antioxidant activity of flavonoids, which is due to their ability to reduce free radical formation and to scavenge free radicals. The capacity of flavonoids to act as antioxidants in vitro has been the subject of several studies in the past years, and important structure-activity relationships of the antioxidant activity have been established. The antioxidant efficacy of flavonoids in vivo is less documented, presumably because of the limited knowledge on their uptake in humans. Most ingested flavonoids are extensively degraded to various phenolic acids, some of which still possess a radical-scavenging ability. Both the absorbed flavonoids and their metabolites may display an in vivo antioxidant activity, which is evidenced experimentally by the increase of the plasma antioxidant status, the sparing effect on vitamin E of erythrocyte membranes and low-density lipoproteins, and the preservation of erythrocyte membrane polyunsaturated fatty acids. This review presents the current knowledge on structural aspects and in vitro antioxidant capacity of most common flavonoids as well as in vivo antioxidant activity and effects on endogenous antioxidants.
4,211 citations