**1. Introduction**

Chemical stress induced by the presence, in a living organism, of an excess of reactive chemical species, generally centered on oxygen (reactive oxygen species), secondary to an increased production of the same and / or to a reduced efficiency of the physiological systems of antioxidant defense. There are many antioxidants, among these there is resveratrol. The history of resveratrol (the *red wine* and pomegranate juice are rich in this substance, chemically it is a triidrostilbene "a derivative stilbenic", synthesized from the vine of red grapes.) 10 20 times more potent than Vitamin E and Glutathione is the most powerful of those produced by the body (prevents arteriosclerosis, cancer and recently even Alzheimer's and delays the appearance of the characteristic signs of old age and can extend life by as much as 30%.). Another powerful antioxidant is hydroxytyrosol. The hydroxytyrosol (1- (2-hydroxy) ethyl-3,4-dihydroxybenzene) is classified as a phytochemical compound expressing strong antioxidant properties. The index ORAC (Oxygen Radical Absorbance Capacity, or the oxygen radical absorption capacity) for hydroxytyrosol totaled 40,000 μmolTE / g, about ten times greater than green tea at least twice compared to CoQ10. In nature, hydroxytyrosol is found in high concentrations in olive vegetation water and also in lower concentrations in the olive leaf. Olives, leaves and olive pulp contain much higher amounts of hydroxytyrosol compared to olive oil. One study showed that a low dose of hydroxytyrosol in rats reduces the consequences of the side effects of oxidative stress induced by smoking [1]. Among the paradoxical antioxidants is creatinine. Creatinine (from the greek κρέας, Kreas, "flesh") is an intermediate of energy metabolism synthesized by the liver about (1 g / day) from arginine, S-adenosyl methionine and glycine and is used in mammalian muscles to regenerate ATP during the first seconds of muscle contraction. Recent reports showed that creatinine displays antioxidant activity which could explain its beneficial cellular effects. Some authors [2] have evaluated the ability of creatinine to protect human erythrocytes and lymphocytes against oxidative damage. Erythrocytes were challenged with model oxidants, 2, 2<sup>0</sup> azobis (2-amidinopropane) dihydrochloride (AAPH) and hydrogen peroxide (H2O2) both in the presence and absence of creatinine. Incubation of erythrocytes with oxidants alone increased hemolysis, met-hemoglobin levels, lipid peroxidation [3] and protein carbonyl content. This was accompanied by decrease in glutathione cellular levels. Antioxidant enzymes and antioxidant power of the cell were compromised while the activity of membrane bound scavenger enzymes were lowered [2]. In a recent paper [4] authors demonstrated that hypertriglyceridemia affects Red Blood Cell (RBC) membrane oxidative status (increase of [malondialdehyde (MDA)] and [4-hydroxynonenal (HNE)] to membrane protein ratio) is increased by high levels of blood cholesterol, but selectively by hypertriglyceridemia [4, 5]. It is known that creatinine protects the erythrocytes by attenuating the AAPH and H2O2 induced alterations [5]. This protective effect was confirmed by electron microscopic analysis which showed that oxidant-induced cell damage was attenuated by creatinine. Thus, creatinine can function as a blood antioxidant, protecting cells from oxidative damage, genotoxicity and can potentially increase their lifespan. Another paradoxical antioxidant is uric acid. Uric acid is an organic molecule of natural origin. Urate is formed as a byproduct in living mammalian organisms higher in purine metabolism. It belongs to the group of oxypurines and is formed from a pyrimidine ring (α) condensed with an imidazole ring (β). Uric acid, despite being a major antioxidant in the human plasma, both correlates and predicts development of obesity, hypertension and cardiovascular disease, conditions associated with oxidative stress [6]. While one explanation for this paradox could be that a rise in uric acid concentration represents an attempted protective response by the host, we review the evidence that uric acid may function either as an antioxidant (primarily in plasma) or pro-oxidant (primarily within the cell). We suggest that it is the pro-oxidative effect of uric acid, that occurs in cardiovascular disease and may have a contributory role in the pathogenesis of this condition. Then finally there are the Polyunsaturated fatty acids. Polyunsaturated fatty acids (PUFAs) are fatty acids that contain more than one double bond in their backbone. This class includes many important compounds, such as essential fatty acids and those that give drying oils their characteristic property. Fatty acid composition and susceptibility to lipid peroxidation induced in vitro by (AAPH) were evaluated in human RBC membranes on days 30 and 180. n-3 PUFA treatment increased

#### *Reducing Compounds Roles in Oxidative Stress Relieving of Human Red Blood Cells DOI: http://dx.doi.org/10.5772/intechopen.99977*

eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) concentrations in RBC membranes in a time-dependent manner in all of the n-3 PUFA groups. These modifications occurred with concomitant dose- and time-dependent increases in the membrane unsaturation index. After 30 d of treatment with n-3 PUFAs, significantly increased in RBC membranes of the intermediate- and high-dose groups. Because of the higher concentration of this antioxidant in these groups, the susceptibility of RBC membranes to peroxidation was decreased. However, after 180 d of treatment, to baseline values and AAPH-induced lipid peroxidation increased in a dose-dependent manner. These results show that high doses of dietary n-3 PUFAs, as well as long-time treatments, affect human RBC susceptibility to lipid peroxidation by changes in fatty acid composition content [7].
