الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
A free radical is very reactive and unstable molecules because it has one or more unpaired electrons in an outer orbital which make it involved in oxidative damage which may be opposed by many antioxidants in the body. Oxidative stress is a shift in the equilibrium between reactive oxidant species, occurring during normal metabolic or any pathological processes in the body, and their protective antioxidant defense mechanisms in favor of reactive oxidant species. Free radicals are involved in pathogenesis of various diseases as, diabetes, stroke, atherosclerosis, inflammatory diseases, cancer. Also oxidative stress plays an important role in the pathophysiology of male infertility as oxidative stress, sperm DNA damage, and apoptosis have been implicated in male infertility. Reactive oxygen species mediate their action through many of the pro-inflammatory cytokines. Human spermatozoa use reactive oxygen species for a physiological purpose ensuring the balanced generation of these potentially harmful, but biologically important, modulators of cellular function. When ROS are present in excessive amounts either due to increased generation or impaired clearance, they can cause extensive sperm DNA structural damage, reduced sperm motility and defective sperm membrane integrity via lipid peroxidation, all of which are important mechanisms behind sperm dysfunction. Spermatozoa are particularly susceptible to oxidative injury due to the abundance of plasma membrane polyunsaturated fatty acids. These unsaturated fatty acids provide fluidity that is necessary for membrane fusion events (e.g., the acrosome reaction and sperm–egg interaction) and for sperm motility. However, the unsaturated nature of these molecules predisposes them to free radical attack and ongoing lipid peroxidation throughout the sperm plasma membrane. Once this process has been initiated, accumulation of lipid peroxides occurs on the sperm surface (this results in loss of sperm motility) and oxidative damage to DNA can ensue. Accurate evaluation of seminal oxidative stress by standardized assays may help in the diagnosis of male infertility. In vivo detection of free radicals is difficult because of their short lifetimes so, lipid peroxidation markers such as, malon dialdehyde, products of oxidatively damaged DNA such as, 8-hydroxy-20-deoxyguanosine, and plasma reactive carbonyl derivative are used as indicators of oxidative stress. Seminal fluid OS levels can also be quantified either by direct methods, such as chemiluminescence assays, cytochrome-c and nitroblue tetrazolium reduction, flow- cytometry, electron spin resonance spectroscopy, xylenol orange-based assay, and by indirect methods which measure the levels of biomarkers of OS, such as thiobarbituric acid reactive substances, isoprostane, DNA damage and total antioxidant capacity. Measuring the degree of OS may identify those patients who could benefit from antioxidant supplementation. The biological effects of free radicals are controlled in vivo by a wide range of antioxidants such as (Vitamin E, Vitamin C &Vitamin A, glutathione, pyruvate, glutathione, Lcarnitine, taurine and hypotaurine) and antioxidant enzymes including (glutathione reductase, glutathione peroxidase, super oxide dismutase and catalase). Seminal plasma and spermatozoa themselves are well endowed with an array of these protective antioxidants to protect spermatozoa from OS, especially, at the post-testicular level. A deficiency in these enzymes has been reported to cause sperm DNA damage and male infertility. A number of investigators have shown that seminal antioxidant capacity is suppressed in infertile men with high ROS levels compared to men with normal levels of ROS. Published studies on dietary antioxidant generally demonstrate a beneficial effect of antioxidants on sperm function. However, the mechanism of action of these antioxidants as well as the optimal type and dosage of antioxidant is unknown. Assessment of oxidative stress status (OSS) may help in the medical treatment of this male factor infertility by suitable antioxidants. Seminal oxidative stress (OS) results from an imbalance between reactive oxygen species (ROS) production and ROS scavenging by seminal antioxidants. Seminal OS is believed to be one of the main factors in the pathogenesis of sperm dysfunction and sperm DNA damage in male infertility. Measurement of the levels of malondialdehyde (MDA) and F2-isoprostanes (IsoPs) by Mass Spectrometry-based methods has become the ”gold standard” biomarkers of oxidative stress. Electron spin resonance (ESR) spectroscopy has considered the “gold standard” technique used to detect free radicals. Infertile men have higher levels of semen reactive oxygen species (ROS) than do fertile men, high levels of semen ROS can cause sperm dysfunction, sperm DNA damage and reduced male reproductive potential. Oral antioxidants could reduce seminal oxidative stress and could improve sperm motility, but has a less predictable impact on sperm concentration and morphology. However the exact mechanism of action of dietary antioxidants and the optimal dietary supplement have not been established.