Scavenging antioxidants

There are, indeed, many biological implications that have been triggered by the advent of fullerenes. They range from potential inhibition of HIV-1 protease, synthesis of dmgs for photodynamic therapy and free radical scavenging (antioxidants), to participation in photo-induced DNA scission processes [156, 157, 158, 159, 160, 161, 162 and 163]. These examples unequivocally demonstrate the particular importance of water-soluble fullerenes and are summarized in a few excellent reviews [141, 1751. 

Bissett DL, Chatterjee R, Hannon DP (1990) Photoprotective effect of superoxide-scavenging antioxidants against ultraviolet radiation-induced chronic skin damage in the hairless mouse. Photodermatol Photoimmunol Photomed 7 56-62... 

Herz, H., Blake, D.R and Grootveld, M. (1994). Multicomponent investigations of the hydrogen peroxide- and hydroxyl radical-scavenging antioxidant capacities of biofluids the roles of endogenous pyruvate and lactate. Free Rad. Res. Commun. (in press). 

The most extensive evidence that supports a role for free radicals in pathological conditions of the brain is provided by studies on experimental models of cerebral ischaemia/reperfusion. Although a burst of free-radical production occurs during the reperfusion phase after temporary cerebral ischaemia, the contribution of this radical burst to brain cell death can not be directly quantified. Perhaps the best way to quantify the contribution of free radicals to brain damage after ischaemia/ reperfusion is to assess damage after treatment with free-radical scavengers or antioxidants. Numerous studies have been reported where free-radical scavengers/ antioxidants have been used to try to ameliorate brain... 

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. 

Radical scavengers - [ANTIOXIDANTS] (Vol 3) -antiaging research [ANTIAG ENG AGENTS] (Vol 2)... 

Free radical scavengers, antioxidants - ebselen, tirilazad... 

TRAP Total peroxyl radical scavenging antioxidant capacity 3 (113)... 

The chain reaction is terminated by reactions that remove radicals that would otherwise produce more allylic radicals by hydrogen abstraction. Examples are the combination of two hydroperoxy radicals leading to nonradical products and molecular oxygen or reaction with a free-radical scavenger (antioxidant) generating a more stable radical. 

Fig. 3 Dual-HPLC plots of two antioxidants trolox and resveratrol. Upper chromatograms show UV profiles registered at 250 nm and lower chromatograms ABTS scavenging (antioxidant activity) profiles registered at 600 nm (negative peak). In (A), trolox was detected with a retention time of 6.2 min. Inset Calibration curve of scavenging activity (peak areas at 600 nm) for different amounts of trolox. In (B), resveratrol was detected at 5.0 min.

Since radical-scavenging antioxidant molecules are consumed in the process of protecting against oxidants, changes in antioxidant activity may also reflect previous or ongoing oxidative stress. Therefore, measurement of antioxidant activity under controlled oxidative stress has been also used to estimate extent of lipid peroxidation. 

CS-grafted copolymers Copolymerisation reactions Modifying the chemical and physical properties of chitin and CS to widen their practical use Tissue engineering, antibacterial and superoxide scavenging (antioxidant) activity... 

There are two major classes of antioxidants and they are differentiated based on their mechanism of inhibition of polymer oxidation chain-terminating or primary antioxidants and hydroperoxide-decomposing secondary antioxidants [5]. Primary or free-radical scavenging antioxidants inhibit oxidation via very rapid chain-terminating reactions. The majority of primary antioxidants are hindered phenols or secondary aryl amines. Generally, hindered phenols are nonstaining, nondiscoloring, and are available in a wide... 

In so-called thermooxidative degradation, primary radicals are produced in the presence of oxygen due to the effects of heat, possibly coupled with mechanical stressing of the plastic. Certain substances like sterically inhibited phenols or amines can trap (scavenge) these radicals. For example, di-tert-butylphenols act as radical scavengers (antioxidants). The reaction scheme described below makes it clear that the oxidation inhibitor is consumed in the process. Thermooxidation can therefore be delayed until the radical scavenger is completely used up. 

Uses Light stabilizer, free radical scavenger, antioxidant for polymers, polyolefins, food-grade polymers... 

A new stabiliser for water pipes has been made available by Clariant. It is a free radical scavenging antioxidant called Hostanox O 310 XP, and is said to have a positive synergism with the same company s UV stabiliser, Hostavin N30 . 

A range of defense systems have evolved to scavenge these species and to repair slight cellular damage. Substances which afford these defense mechanisms are known as antioxidants and can be classified into two categories, preventative antioxidants and scavenging antioxidants. 

The radical scavenging antioxidants are non-enzymatic and are found in plasma, lipoproteins and membranes. It is these types of antioxidant reactions that this Chapter will concentrate on, since many of these antioxidants can be increased by dietary supplementation and, therefore, could be used medicinally to prevent oxidation by radicals and other reactive oxygen species. 

---