The present review aims to high light on the oxidative stress, and prevention by internal antioxidants and external antioxidants by some natural products possessing antioxidant properties. Oxidative stress occurs when the balance between reactive oxygen species (ROS) formation and detoxification favors an increase in ROS levels, leading to disturbed cellular function. ROS causes damage to cellular macromolecules causing lipid peroxidation, nucleic acid, and protein alterations. Their formation is considered as a pathobiochemical mechanism involved in the initiation or progression phase of various diseases such as atherosclerosis, ischemic heart diseases, diabetes, and initiation of carcinogenesis or liver diseases. In order to maintain proper cell signaling, it is likely that a number of radical scavenging enzymes maintain a threshold level of ROS inside the cell. However, when the level of ROS exceeds this threshold, an increase in ROS production may lead to excessive signals to the cell, in addition to direct damage to key components in signaling pathways. ROS can also irreversibly damage essential macromolecules. Protein-bound thiol and non-protein-thiol are the major cytosolic low molecular weight sulfhydryl compound that acts as a cellular reducing and a protective reagent against numerous toxic substances including most inorganic pollutants, through the –SH group. Hence, thiol is often the first line of defense against oxidative stress. Flavonoids have been found to play important roles in the non-enzymatic protection against oxidative stress, especially in the case of cancer. Flavonoids have occurred widely in tea, fruit, red wine, vegetables, and cocoas. Flavonoids, including flavones, flavanone, flavonols, and isoflavones, are polyphenolic compounds which are widespread in foods and beverages, and possess a wide range of biological activities, of which anti-oxidation has been extensively explored. It can be concluded that oxidative stress causes irreversible damage in cellular macromolecules that leads to initiation of various diseases such as atherosclerosis, ischemic heart diseases, liver diseases, diabetes, and initiation of carcinogenesis. Antioxidants inhibit reactive oxygen species production and scavenging of free radicals. Therefore, the review recommends that high consumption of natural foods that are rich in antioxidants will provide more protection against toxic agents and related diseases.

Nephrotoxicity is one of the most common kidney problems and occurs when the body is exposed to a drug or toxin. Natural sources of antioxidants may serve as a vital source of potentially useful new compounds for the development of an effective therapy to combat a variety of kidney problems. Natural antioxidants have a variety of biochemical actions such as inhibition of reactive oxygen species production, scavenging of free radicals. The present review aims to summarize the recent articles which studied some of the nephrotoxic agents, and alleviation of nephrotoxicity using of some natural products possessing antioxidant properties. Our review shows the oxidative damage and renal disorders induced in human and experimental animals by nephrotoxic agents such as gentamicin, alcohol, nicotine, adenine, glycerol, ethylene glycol, sodium nitrite, mercuric chloride, AlCl 3 , lead acetate, carbon tetrachloride (CCl 4 ), furosemide, carbendazim, diazinon, heat stress, and γ-radiation. Also, nephrotic disorders caused in diabetic rats, patients, cirrhotic ascetic patients, and ischemia-reperfusion. Administration of natural sources of antioxidants such as curcumin, garlic, fenugreek, parsley, peppermint, pomegranate, propolis, olive leaves, rosemary, and sesame attenuated both physiological and histopathological alterations induced in the kidney by the nephrotoxic agent and certain diseases. The nephroprotective effect of the former natural sources of antioxidants may be due to the enhancement of antioxidant activity and inhibition of tissue lipid peroxidation. It can be concluded that administration of curcumin, garlic, fenugreek, parsley, peppermint, pomegranate, propolis, olive leaves, rosemary, and sesame showed a remarkable kidney protection against nephrotoxic agents, and diseases induced renal dysfunctions in human and experimental animals. So, the present study recommended that the consumption of these natural sources of antioxidants may be useful for human exposure to nephrotoxic agents and patients who suffer from renal diseases.

Cyclosporin A is a compound widely used as an immunosuppressive drug, particularly, in case of kidney transplantation to prevent rejection of transplanted organ. This study aimed to investigate the bad side effect of acute and chronic treatment with cyclosporin A on liver and kidneys by measuring liver enzymes and kidney function tests in serum. Male rats were used as experimental model in this study. The results of this study concluded that, chronic treatment with cycloosprin A leads to increase in serum urea, creatinine, and uric acid significantly compared to control, also, ALT and Alkaline phosphatase activities in serum were increased by chronic administration of cyclosporine A for four weeks. Decrease of serum albumin and total protein were observed significantly compared to control groups.

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In chronic kidney failure, there is impairment in the excretion of toxic non-volatile solutes, with consequent increase in the plasma concentrations of all metabolites derived mainly from protein metabolism, characterized by increased urea and creatinine, the prevalence and severity of anemia are related to the kidney disease stage and the relative deficiency or reduction in erythropoietin production is the main cause. This study aimed at checking the correlation between anemia and chronic kidney diseases in patients who underwent hemodialysis in Sabratha Hospital in the West of Libya. This study was conducted on 60 patients (36 males and 24 females) with chronic renal failure from October 2015 to April 2016 and a group of 40 (20 males and 20 females) individuals as control. The results of the study concluded that there is a correlation between progression of chronic kidney diseases and reduction in hemoglobin, red blood cells count, hematocrit, and serum iron.Keywords: Chronic kidney diseases, Chronic kidney disease, Anemia, Renal failure