hepatocytes , which make up the majority of the liver structure , are very active in the metabolism of exogenous chemicals , and this is one of the major reasons why the liver is a target for toxic substances ( 1 ) . in recent studies , aging and related diseases , such as cancer and coronary heart disease and neurodegenerative disorders such as alzheimer s disease were found to be related to oxidative and free radical mediated reactions ( 2 ) . one of the most important of free radicals , reactive oxygen species ( ros ) are generated which cause oxidative stress ( 3 ) . the tipping of the balance towards prooxidant status in oxidative stress induced damage to cellular and extra - cellular macromolecules , such as proteins , lipids and nucleic acids , and affects the immune function ( 4 ) . endogenous or dietary factors play a major role in the antioxidative defense of the organism against the ros generated during normal cellular aerobic respiration ( 5 ) . therefore , it is generally assumed that increased intake of dietary antioxidants may help to shift the balance towards an adequate antioxidant status . it was postulated that incubation of lipophylic agent with rat hepatocytes , may prevent against oxidative damage . to test this hypothesis , lycopene and ubiquinol-10 lycopene is a carotenoid found in high quantities in tomatoes and tomato - rich products and a potent donor antioxidant ( reductant ) , which increases the lipoprotein resistance against the oxidative modification . in lipid solutions and dispersions , it inhibits formation of radicals linearly with time until consumed in the process ( 7 ) . ubiquinol-10 , the reduced form of ubiquinone-10 ( coenzyme q10 ) , is a well - known proton - electron carrier in inner mitochondria membrane and a potent lipophylic antioxidant in different cell membranes . it is well established that both ubiquinols and ubiquinones are active against lipid peroxidation in mitochondria and liposomes but that the quinols are much more powerful antioxidants than the corresponding quinones ( 8) . recently , we reported that both compounds can protect human lipoprotein more efficiently against lipid peroxidation than antioxidant vitamins ( 9 , 10 ) . the aim of the present study was to investigate the effects of lycopene and ubiquinol-10 on liver injury induced by tert - butyl hydroperoxide ( t - bhp ) , a short - chain analogue of lipid peroxide in rat livers chemicals : tert - butyl hydroperoxide ( t - bhp ) , thiobarbituric acid ( tba ) , lycopene , ubiquinol-10 and other chemical substances were prepared from merck , germany . animals : in this study , male wister rats ( with a body weight of 25020 g ) were purchased from pasteur institute tehran , iran . these animals were housed in laboratory cages and maintained on a 12 hr light - dark cycle with free access to food and water throughout the study . isolation and culture of rat hepatocytes : rat hepatocytes were prepared by collagenase perfusion , as described previously ( 11 ) . the liver were then removed , minced and homogenized at 4oc in 3ml per g liver , of a buffer made of 20 mm tris - chloride , 0.15 m nacl , 1 mm cacl2 and 1 m pmsf ( phenyl methyl sulfonyl fluride ) with ph=7.4 . the resulting filtrate was quickly frozen in liquid nitrogen and can be stored at -70 oc for performing the other experiments . in vitro hepatocytes treatment : first , to the primary cultured rat hepatocytes , various doses of each : lycopene or ubiquinol-10 ( 0 , 10 , 20 and 50 mol / l ) were added to the rat hepatocytes for 4 hr at 37oc . then , hepatocytes were incubated with t - bhp ( 1.5 mm ) for 30 min at 37oc ( 12 ) . lipid peroxidation assay : hepatocytes were pretreated with lycopene and ubiquinol-10 , and then with t - bhp as described above . the lipid peroxidation product was assayed according to an improved tba method by spectrophotometer at 532 nm wavelenght absorption , using 1,1,3,3-tetra - methoxypropane as a standard ( 13 ) . the results were expressed as nmol of malondialdehyde ( mda ) equivalents per mg protein . the student s t - test was used to perform the statistical comparison between the group by one - way analysis of variance . cytotoxicity of t - bhp : the tba method showed that t - bhp expressed toxicity effects to the primary cultures of rat hepatocytes in 0.5 , 1 and 1.5 mm concentrations , and in 1.5 mm concentration the highest toxicity effect was observed ( table 1 ) . effects of lycopene on t - bhp - induced hepatotoxicity : the effects of lycopene on the cytotoxicity induced by t - bhp in the primary cultured hepatocytes were expressed by the mda formation . as shown in table 2 , the mda formation caused by t - bhp ( 1.5 mm for 30 min ) / l , p<0.001 , 46% for 20 mol / l , p<0.001 , and 20% for 10 effects of ubiquinol-10 on t - bhp - induced hepatotoxicity : the effects of ubiquinol-10 on the cytotoxicity induced by t - bhp in the primary cultured hepatocytes were expressed by the mda formation . as shown in table 3 , the mda formation caused by t - bhp ( 1.5 mm for 30 min ) / l , p<0.001 , 26% for 20 mol / l , p<0.01 , and 10% for 10 we employed t - bhp , a short - chain analog of lipid peroxides to induce acute oxidative damage in cultured rat hepatocytes . the model of t - bhp induced acute hepatic damage in animals has been used in several studies , and the capacity of a test compound to reduce the injurious effects or to preserve the normal hepatic physiological mechanisms which have been disturbed by t - bhp is the index of its hepato - protective effect ( 1 , 14 ) . reactive oxygen species ( ros ; .oh , o2- , ro , roo , no ) can originate from a number of internal and external sources , such as metabolic reactions , infections , dietary intake and cigarette smoking . the body , however , possesses defense mechanisms to reduce the oxidative damage , and such mechanisms use both enzymes and antioxidant nutrients or medicine to arrest the damaging properties of excited oxygen species . only when the normal protective mechanism breaks down , or when the effectiveness of antioxidant sources is reduced , which leads to the excessive amount of free radicals in the body , the irreversible oxidative damage may occur . a great number of studies have suggested that antioxidant nutrients and/or medicines play a protective role for the human health ( 3 , 15 ) . the first employs the microsomal cytochrome p-450 system leading to the production of ros that initiate lipid peroxidation ( 16 ) ; while the second concerns a reaction involving glutathione peroxidase and its substrate glutathione ( gsh ) . decreased gsh is considered to be a major event in t - bhp- induced toxicity ( 17 ) . in the hepatotoxicity and lipid peroxidation experiments , lycopene and ubiquinol-10 were shown to possess a high antioxidative and protective capacity against the injury induced by t - bhp , as reflected in the decreased formation of mda . lycopene and ubiquinol-10 are known to be a highly efficient lipid - soluble antioxidants in the protection of lipids in a variety of biological and model systems including lipoproteins and liposomes ( 18 , 19 ) . it is generally assumed that they may exhibit their protective effects by preventing the formation of lipid free radicals and/or by eliminating them . on the other hand , the possibility that the inhibition of lipid peroxidation is related to their interactions on the lipid structure of the hepatocytes membranes needs further investigation . lycopene and ubiquinol-10 contain shielding methyl ( -ch3 ) groups and are optimally positioned in the membranes by their phytyl side - chain . also , the inhibition of photosensitized oxidants of lipids and lipoproteins by both compounds mediated by singlet oxygen have been demonstrated ( 20 ) . incubation of lycopene and ubiquinol-10 with hepatocytes over a long period of time may enrich their membranes sufficiently to make them less susceptible to oxidative reactions . in the present study , lycopene and ubiquinol-10
free radicals especially reactive oxygen metabolites can damage dna , protein , enzymes , and membrane lipids . 
 lipid peroxidation in hepatocyte membrane may be involved in hepatic diseases . 
 antioxidants may inhibit this reaction . 
 due to oxidant - antioxidant imbalance , free radicals may cause destructive effects . for several years 
 , scientists tried to find antioxidant compounds . in this study , the effects of lycopene and ubiquinol-10 on the oxidative stress in rat hepatocytes induced by t - buthyl hydroperoxide was determined . 
 first , rat hepatocytes were isolated and then incubated in the presence of tert - buthyl hydroperoxide and the amount of malondialdehyde , as a marker of lipid peroxidation , was determined . 
 then , this reaction was performed in the presence of various concentrations of each lycopene and ubiquinol-10 , and the malondialdehyde level was determined.the results of this study showed that in the presence of various concentrations of lycopene and ubiquinol-10 the levels of lipid peroxidation products significantly decreased ( p<0.05 ) . 
 thus , lycopene and ubiquinol-10 have inhibitory effects on lipid peroxidation reaction . 
 this study showed the potential utility of lycopene and ubiquinol-10 in prevention of hepatic dysfunction .