Radicals flavonoid activity

As discussed previously, UV-C irradiation increased the phenol and flavonoid content such compounds present high radical-quenching activity by themselves (Robles-Sanchez and others 2007). Few studies have been reported specifically about the effect of UV-C irradiation on antioxidant capacity of treated fruit. However, Fan and others... 

Huge literature on biological functions of flavonoids and their antioxidant and free radical scavenging activities successfully competes with work on antioxidant effects of vitamins E and C. Flavonoids have been reported to exert multiple biological effects and exhibit antiinflammatory, antiallergic, antiviral, and anticancer activities [85 89], However, considering flavonoids as the inhibitors of free radical-mediated processes, two types of their reactions should be discussed flavonoids as free radical scavengers (antioxidants) and flavonoids as metal chelators. 

Antioxidant activity of flavonoids has already been shown about 40 years ago [90,91]. (Early data on antioxidant flavonoid activity are cited in Ref. [92].) Flavonoids are polyphenols, and therefore, their antioxidant activity depends on the reactivity of hydroxyl substituents in hydrogen atom abstraction reactions. As in the case of vitamins E and C, the most studied (and most important) reactions are the reactions with peroxyl radicals [14], hydroxyl radicals [15], and superoxide [16]. 

It has been established that the free radical scavenger activity of flavonoids is responsible for the antioxidant effect [95,96], The beneficial antitumour effect of quercetin has also been demonstrated [97,98],... 

Om A, Kim JH. 2008. A quantitative structure-activity relationship model for radical scavenging activity of flavonoids. J Med Food 11 29-37. 

Husain, S.R., Cillard, J., and Cillard, P. 1987. Hydroxyl radical scavenging activity of flavonoids. Phytochemistry 26, 2489—2491. 

Citrus sinensis (L.) Osbeck - laranjeira, laranja Tranquilizer Leaf (infusion or decoction, ingested) Caboclos [57,59] Quilombolas [54] Flavonoids [206,207] essential oils [208,209] phenolic compounds Coumarins, fatty acids [210,201] quinoline alkaloids [211,212] Radical scavenging activity [276] antioxidant activity [277] inotropic effect [278]... 

Vangueria infausta [umntulu, wild medlar] (Mimosaceae) root bark decoction is used for chest pain. The root bark contains alkaloids, anthranoids, flavonoids, glycosides, polyphenols, saponins and steroids (15). A biflavonoid with radical scavenging activity and flavonoids with antimicrobial properties have been isolated from the aerial part of the plant (58). 

Amic, D., Davidovic-Amic, D., Beslo, D. and Trinajstic, N. (2003) Structure-radical scavenging activity relationships of flavonoids. Croat. Chem. Acta, 76, 55-61. 

Flavonoids possess free-radical scavenging activity [128] and the MAA my-cosporine-glycine also exhibits moderate antioxidant activity [103], These compounds may be additional sources of protection against photooxidative stress due to the high concentrations of oxygen in photosynthetic symbioses. Imino-type MAAs such as palythine and shinorine had no detectable antioxidant activity [103],... 

Four basic mechanisms of such action have been described and are applicable to flavonoids (1) free radical scavenging activity [16], (2) quenching of singlet oxygen [17], (3) chelation of transition metals [18],... 

ANTIOXIDANT ACTIVITY OF FLAVONOIDS Free Radical Scavenging Activity... 

There are many studies about the relation between the free oxygen radical scavenging activities of many flavonoids and their effects on the enzymes which take part in the metabolism of arachidonic acid, cyclooxygenase (COX) and lipoxygenase (LOX). Duneic [182] shows that the antiradical action affects the COX activity in several ways. In most of the cases, at high substrate concentrations the enzymatic activity was intensified and at low concentrations it was inhibited. Apparently, the influence of the antiradical properties on the activity of enzymatic metabolism of the arachidonic acid in vitro might also be due to the effect of these agents on the active center of the enzymes. 

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