Antioxidant-free systems

Biological Antioxidant Models. Tea extracts, tea polyphenol fractions, and purified catechins have all been shown to be effective antioxidants in biologically-based model systems. A balance between oxidants and antioxidants is critical for maintenance of homeostasis. Imbalances between free radicals and antioxidants may be caused by an increased production of free radicals or decreased effectiveness of the antioxidants within the reaction system. These imbalances can be caused by the radicals overwhelming the antioxidants within the system, or by an excess of antioxidants leading to a prooxidant functionaHty (105—118). When antioxidant defense systems are consistently overwhelmed by oxidative reactions, significant damage can... 

Human chronic inflammatory diseases are characterized by populations of cells with altered regulation and function. A large body of evidence suggests that many of these cellular abnormalities may be linked to an increase in the production of free radicals and/or deficiencies of antioxidant defence systems. Oxygen free radicals attack cell structures, altering their function, and are cytotoxic. They have therefore been implicated in the pathogenesis of rheumatoid arthritis as well as many other human diseases (HaUiwell, 1991). 

The efficient removal of O2 and H2O2 vvill diminish OH formation and therefore antioxidant defence systems have evolved to limit their accumulation. Enzymic and low molecular weight antioxidants exist to scavenge free radicals as self-protection mechanisms. Some proteins exhibit antioxidant properties because they chelate transition-metal catalysts. The significance of antioxidants in relation to inflammatory joint disease is discussed below. 

FoS had obvious antioxidant effect. In cell-free system after the addition of hydrogen peroxide solution the extinguishing of fluorescence of 2 ,7 -dichlorofluo-rescein was evident with H202 concentrations at 97 and 194pM. At the substantially higher concentration of the latter (970 pM) a slight nonsignificant overlap of control level was evident (Fig. 7.2). These data confirm the antioxidant activity of pristine C60. On the other hand, they indicate that it is limited to a certain antioxidant capacity (Fig. 7.2). 

A study on the mechanism of BAO effects showed that there is a whole system of relations between separate indices of cell metabolism that vary under the aetion of antioxidants. Investigation of the physicochemical regulatory system maintaining the level of free-radical reactions in lipids, on the one hand, and regulating the metabolism of membrane lipids and the rate of consumption of antioxidants in lipids, on the other hand, has been further developed [46, 47]. The components of this system are antioxidants, free radieals. 

Onodera, K., Omoi, N.O., Fukui, K., Hayasaka, T., Shinkai, T., Suzuki, S., Ahe, K., Urano, S. (2003). Oxidative damage of rat cerebral cortex and hippocampus, and changes in antioxidative defense systems caused hy hyperoxia. Free Radio. Res. 37 367-72. 

Oxidative stress is a harmful condition that occurs due to an excess of free radical and oxidant production over the primary antioxidant defense systems. Consequently the undefeated free radicals and oxidants are able to react and modify cellular components including proteins. 

In washed human platelets, NDGA inhibited the formation of 12-LOX products as well as the COX product 12-hydroxyheptadecatrienoic acid (12-HHT), with an IC50 of 5 pM, while boswellic acids (mixture of a- and P-isomers) at concentrations up to 400 pM exerted no effect. In addition, in a cell-free system, the non-enzymatic peroxidation of AA by iron (II)-ascorbate was not affected by boswellic acid at concentrations up to 400 pM, whereas NDGA abolished the peroxidation of AA in this test at a concentration of 10 pM. These results suggest that the activity of boswellic acids is selective in the 5-LOX pathway, and the mechanism of inhibition is different from that of the classic antioxidant 5-LOX inhibitors (NDGA, caffeic acid, quercetin) [96]. 

Substantial LPO occurs only when cellular defense mechanisms have been weakened or overcome by prolonged oxidative stress. Hence understanding of the balance between free radical generation and antioxidant defense systems is critical to the understanding and control of free radical reactions in biology and medicine. ... 

K2. Kaplan, I. V., Attaelmannan, M., and Levinson, S. S., Fibrinogen is an antioxidant that protects beta-lipoproteins at physiological concentrations in an in vitro cell free system. Atherosclerosis 158, 455 63 (2001). 

Porta, C. et ah. Antioxidant enzymatic system and free radicals pathway in two different human cancer cell lines, H r/ca cer Res., 16 (5A), 2741,1996. 

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