[Activity of enzymatic detoxification systems in the mice liver under conditions of different retinoid provision].

The activity of cellular components of liver detoxification system was studied under the conditions of the absence of vitamin A stores. It is shown that a decrease of p-hydroxylase and N-demethylase activity of cytochrome P-450 simultaneously with a decrease of glutathione-S-transferase activity takes place in the liver microsomal fraction of vitamin A-deficient animals. At the same time the absence of retinoid stores in knock-out animals influences the decrease of only p-hydroxylase activity of cytochrome P-450 system. The increase in glutathione-S-transferase activity is observed in the liver postmicrosomal fraction in mice, kept on vitamin A-deficient diet, while its parametres in knock-out group animals were not statistically different compared to the control.

Diverse action of acrylamide on cytochrome P450 and glutathione S-transferase isozyme activities, mRNA levels and protein levels in human hepatocarcinoma cells.

Humans are exposed to acrylamide in their diet and cigarette smoke. Acrylamide is metabolized into glycidamide by CYP2E1. However, very few studies regarding the effects of acrylamide on cytochrome P450 and Glutathione S-Transferase (GST) isozymes have been pursued. The aim of this study is to elucidate the effects of acrylamide on cytochrome P450 and GST isozymes in HepG2 cell line. Treatment with 1.25 and 2.5 mM acrylamide caused 9.5- and 3.7-fold increases and 4.0- and 3.3-fold increases in CYP1A-associated ethoxyresorufin O-deethylase (EROD) and methoxyresorufin O-demethylase (MROD) activities, respectively. These increases were consistent with increases in mRNA and protein levels of these isozymes. Similarly, CYP2E1-associated aniline 4-hydroxylase (ANH) activity, protein levels, and mRNA levels increased 2.1- and 2.6-fold, 2.4- and 3.2-fold, and 1.4- and 1.9-fold following 1.25 and 2.5 mM acrylamide treatments, respectively. In addition, GST-mu activity was increased 2.4- and 5.1-fold by acrylamide. Moreover, GST-mu mRNA and protein levels increased twofold as a result of acrylamide treatment. In contrast, GST-pi protein and mRNA levels decreased significantly. In conclusion, human cell exposure to acrylamide causes an increase in the levels of carcinogenicity and toxicity and a disturbance in drug metabolism, possibly due to complex effects on P450 and GST isozymes.

Reversal of experimental ethanol-induced liver steatosis by borage oil.

The aim of study was to evaluate the hepatoprotective effect of borage oil containing predominantly gamma-linolenic acid in rats with alcoholic steatohepatitis. Liver of ethanol-treated animals was characterized by fatty and hydropic dystrophies. Liver triglyceride contents and activitiies of serum marker enzymes were significantly increased. Ethanol increased nicotinamide adenine dinucleotide phosphate hydrogen (NADPH)-induced chemiluminescence and the contents of liver thiobarbituric acid reactive substances (TBARS). The reduced glutathione content in the liver was decreased. Ethanol enhanced liver microsomal cytochrome P-450 (CYP450) content, aniline p-hydroxylase and amydopyrine-N-demethylase activities. The treatment with borage oil improved the liver morphology, decreased triglyceride contents and normalized serum marker enzyme activities. Borage oil developed an antioxidant effect in ethanol-treated rats. The treatment with this compound decreased NADPH-induced chemiluminescence and the content of lipid peroxidation products. Borage oil normalized CYP450 content compared with the ethanol-treated group. CYPI450 2E1 isoform is a main source of free oxygen radicals in the liver of ethanol-treated rats and we propose that the antioxidant effect of borage oil is realized via the normalization of CYP450 content and activities of CYP450-related microsomal oxidases, as borage oil can improve the lipid surrounding of CYP450. In our opinion, the hepatoprotection by borage oil in alcoholic steatosis is connected with its antioxidant properties.

Nifedipine lowers cocaine-induced brain and liver enzyme activity and cocaine urinary excretion in rats.

The aim of this study was to see how nifedipine counters the effects of cocaine on hepatic and brain enzymatic activity in rats and whether it affects urinary excretion of cocaine. Male Wistar rats were divided in four groups of six: control, nifedipine group (5 mg kg-1i.p. a day for five days); cocaine group (15 mg kg-1i.p. a day for five days), and the nifedipine+cocaine group. Twenty-four hours after the last administration, we measured neuronal nitric oxide synthase (nNOS) activity in the brain and cytochrome P450 quantity, ethylmorphine-N-demethylase, and anilinehydroxylase activity in the liver. Urine samples were collected 24 h after the last cocaine and cocaine+nifedipine administration. Urinary cocaine concentration was determined using the GC/MS method.Cocaine administration increased brain nNOS activity by 55 % (p<0.05) in respect to control, which indicates the development of tolerance and dependence. In the combination group, nifedipine decreased the nNOS activity in respect to the cocaine-only group.In the liver, cocaine significantly decreased and nifedipine significantly increased cytochrome P450, ethylmorphine-N-demethylase, and anilinehydroxylase in respect to control. In combination, nifedipine successfully countered cocaine effects on these enzymes.Urine cocaine excretion in the cocaine+nifedipine group significantly dropped (by 35 %) compared to the cocaine-only group.Our results have confirmed the effects of nifedipine against cocaine tolerance and development of dependence, most likely due to metabolic interactions between them.

Variability of microsomal oxidation and porphyrin metabolism in rats.

An inverse relationship between erythropoiesis intensity and microsomal oxidation level has been detected during the early postnatal period in rats with high resistance to hypoxia.

Indigofera aspalathoides protection against 20-methylcholanthrene-induced experimental fibrosarcoma growth after transplantation in rats - role of xenobiotic drug metabolizing enzymes.

A large number of active principles from traditional medicinal plants have been reported to have chemopreventive properties. In the present study, therapeutic efficacy of an aqueous extract of Indigofera aspalathoides against growth of transplanted experimental fibrosarcomas in Wistar strain male albino rats was tested. Tumors which appeared about six weeks after implantation were highly localized and were maintained by serial transplantation. Rats were divided into four groups. Group I served as normal control animals. Group II were fibrosarcoma bearing animals. Group III were animals with fibrosarcoma treated with Indigofera aspalathoides aqueous extracts at a dose of 250 mg/kg. b. w. per day for 30 days. Group IV animals were treated with aqueous extract of Indigofera aspalathoides alone. Reduction in tumor weight was noted in Group III as compared to II. The levels of cytochrome C in liver and kidney, the levels of cytochrome P450 and cytochrome b5 in liver microsomes, phase I biotransformation enzymes NADPH-cytochrome P450, NADPH-cytochrome b5, and aniline hydroxylase, and the phase II enzymes glutathione-S-transferase and UDP glucuronyl transferase indicated that their modulation played a role in the therapeutic efficacy of Indigofera aspalathoides against experimental fibrosarcoma.

Effects of Supplementation with a Schizandrin C Derivative DDB-mixed Preparation (DWP-04) on Antioxidant Activity in Cisplatin-induced Nephrotoxicity in Rats / 대한신장학회지

PURPOSE: This study investigated the effect of reducing cisplatin induced nephrotoxicity with DWP-04 that is the compound of Schizandrin C derivative biphenyldimethyl dicarboxylate (DDB), glutathione and selenium. For the purpose of observation is that how DWP-04 has influence on mechanism of reducing cisplatin induced nephrotoxicity with renal function test, free radical formation and detoxification enzyme system in renal tissue. METHODS: Five groups of rats were dosed with vehicle, cisplatin (2 mg/kg i.p.), cisplatin+DWP-04 (100, 200 mg/kg po), or cisplatin+sodium thiosulfate (200 mg/kg i.p.) daily for 4 weeks. RESULTS: Serum creatinine, lactate dehydrogenase and activity of hydroxy radical increased in the cisplatin group and suppressed in the cisplatin+DWP-04 group compared to the cisplatin group. The renal tissue concentration of lipid peroxidase and lipofuscin were increased in the cisplatin group compared to the other groups. The activity of aminopyrine N-demethylase, aniline hydroxylase, aldehyde oxidase and xanthine oxidase, of which free radical formation system in kidney was also decreased in the cisplatin+DWP-04 group compared to the cisplatin and cisplatin+sodium thiosulfate group. The activity of detoxification system of free radical, such as glutathione S-transferase, superoxide dismutase, catalase and glutathione peroxidase were markedly increased in the cisplatin+DWP-04 group than the cisplatin and the cisplatin+sodium thiosulfate group (p<0.05). CONCLUSION: It can be concluded that the mechanism of decreasing cisplatin-induced nephrotoxicity by DWP-04 is that the decreasing of the amount of lipid peroxide and lipofuscin in the renal tissue by increasing activity of the antioxidant defense system and the decreasing of reactive oxygen species by increasing detoxification enzyme activity.

The effects of Urtica dioica L. leaf extract on aniline 4-hydroxylase in mice.

The effects of hydroalcoholic (80% ethanol-20% water) extract of Urtica dioica L. on microsomal aniline 4-hydroxylase (A4H) were investigated in the liver of Swiss albino mice (8- 10-weeks-old) treated with two doses (50 and 100 mg/kg body weight, given orally for 14 days ). The activities of A4H showed a significant increase in the liver at both dose levels of extract treatment. The hydroalcoholic extract of Urtica dioica induced the activities of A4H that had been increased by treatment of metal ions (Mg2+ and Ca2+) and the mixture of cofactors (NADH and NADPH). At saturated concentration of cofactor, microsomal A4H exhibited significantly even higher activities in the presence of the mixture of cofactors than NADPH and NADH. Mg2+ and Ca2+ ions acted as stimulants in vitro. The present results suggest that the hydroalcoholic extract of Urtica dioica may have modalatory effect on aniline hydroxylase at least in part and enhance the activity of A4H adding metals ions and cofactors.

[Effects of ethyl acetate extract of Semen Hoveniae on liver microsomal cytochrome P450 isoenzyme in rat].

OBJECTIVE: To investigate the effects of the ethyl acetate extract of Semen Hoveniae (ESH) on liver microsomal cytochrome P450 isoenzyme in rats. METHOD: The rats were given orally the ESH in the doses of 0.14, 0.17, 0.2 g x kg (equivalent to the crude herb) for 10 days respectively. Rat liver microsomal cytochrome P450, NADPH-Cyt C reductase, erythromycin N-demethylase (ERD), Aniline hydroxylase (ANH), aminopyrine N-demethylase (ADM) activities were quantitated by UV chromatography. The levels of mRNA expression of CYP1A1, CYP2C11, CYP2E1 and CYP3A1 were detected by semi-quantitative reverse transcripatase-polymerase chain reaction (RT-PCR). RESULT: The cytochrome P450 content, NADPH-Cyt C reductase activities and erythromycin N-demethylase (ERD) activities were not affected. Aniline hydroxylase (ANH) activities in liver were decreased by up to35.1%; aminopyrine N-demethylase (ADM) activitiesin liver were increased by up to 42.4%. The mRNA expression of CYP1A1, CYP2C11 and CYP3A1 were found to be increased markedly. CONCLUSION: A specific effect of ESH on liver microsomal cytochrome P450 isoenzyme in rats was observed in this investigation. ESH had various effects on liver microsomal cytochrome P450 isoenzyme.

Propolis protects CYP 2E1 enzymatic activity and oxidative stress induced by carbon tetrachloride.

Induction of CYP 2E1 by carbon tetrachloride (CCl(4)) is one of the central pathways by which CCl(4) generates oxidative stress in hepatocytes. Experimental liver injury was induced in rats by CCl(4) to determine toxicological actions on CYP 2E1 by microsomal drug metabolizing enzymes. In this report, ethanolic extract of propolis at a dose of 200 mg/kg (po) was used after 24 h of toxicant administration to validate its protective potential. Intraperitoneal injection of CCl(4) (1.5 ml/kg) induced hepatotoxicity after 24 h of its administration that was associated with elevated malonyldialdehyde (index of lipid peroxidation), lactate dehydrogenase and gamma-glutamyl transpeptidase release (index of a cytotoxic effect). Hepatic microsomal drug metabolizing enzymes of CYP 2E1 showed sharp depletion as assessed by estimating aniline hydroxylase and amidopyrine N-demethylase activity after CCl(4) exposure. Toxic effect of CCl(4) was evident on CYP 2E1 activity by increased hexobarbitone induced sleep time and bromosulphalein retention. Propolis extract showed significant improvement in the activity of both enzymes and suppressed toxicant induced increase in sleep time and bromosulphalein retention. Choleretic activity of liver did not show any sign of toxicity after propolis treatment at a dose of 200 mg/kg (id). Histopathological evaluation of the liver revealed that propolis reduced the incidence of liver lesions including hepatocyte swelling and lymphocytic infiltrations induced by CCl(4). Electron microscopic observations also showed improvement in ultrastructure of liver and substantiated recovery in biochemical parameters. Protective activity of propolis at 200 mg/kg dose was statistically compared with positive control silymarin (50 mg/kg, po), a known hepatoprotective drug seems to be better in preventing hepatic CYP 2E1 activity deviated by CCl(4). These results lead us to speculate that propolis may play hepatoprotective role via improved CYP 2E1 activity and reduced oxidative stress in living system.

Effects of diabetes on rabbit kidney and lung CYP2E1 and CYP2B4 expression and drug metabolism and potentiation of carcinogenic activity of N-nitrosodimethylamine in kidney and lung.

There are limited number of studies regarding the influence of diabetes on the regulation of cytochrome P450s and associated drug metabolizing enzyme activities especially in extrahepatic tissues such as kidney. However, there is almost no such study in lung. Alloxan-induced diabetes did not change CYP2B4 expression as measured with immunoblot analysis and associated enzyme, benzphetamine N-demethylase, activity in rabbit kidney and lung. Induction of cytochrome P4502E1 by diabetes was identified by immunochemical detection on Western blots in the lung and kidney microsomes of rabbits. In parallel to CYP2E1 induction, aniline 4-hydroxylase and p-nitrophenol hydroxylase activities were markedly increased in diabetic rabbit lung and kidney. CYP2B4 and CYP2E1 dependent drug metabolism did not show any tissue variation in diabetic rabbit. These findings are in contrast to those of rats, mice and hamster. The results of the present work, in combination with those of the previous work [Arinç, E., Arslan, S., Adali, O., 2005. Differential effects of diabetes on CYP2E1 and CYP2B4 proteins and associated drug metabolizing enzyme activities in rabbit liver. Arch. Toxicol. 79, 427-433], indicate the existence of species-dependent response of CYP-dependent drug metabolizing enzymes to diabetes. A procarcinogen and food contaminant, N-nitrosodimethylamine (NDMA), is converted to its carcinogenic form after it is activated with NDMA N-demethylase. In the current study, a statistically significant increase of liver, kidney and lung NDMA N-demethylase activity associated with CYP2E1 was shown in diabetic rabbit. Thus, it is expected that, the risk of nitrosamine induced carcinogenesis will be greater in liver, kidney and lung of the diabetic subjects.

Effects of ethyl acetate extract of Semen Hoveniae on liver microsomal cytochrome P450 isoenzyme in rat / 中国中药杂志

<p><b>OBJECTIVE</b>To investigate the effects of the ethyl acetate extract of Semen Hoveniae (ESH) on liver microsomal cytochrome P450 isoenzyme in rats.</p><p><b>METHOD</b>The rats were given orally the ESH in the doses of 0.14, 0.17, 0.2 g x kg (equivalent to the crude herb) for 10 days respectively. Rat liver microsomal cytochrome P450, NADPH-Cyt C reductase, erythromycin N-demethylase (ERD), Aniline hydroxylase (ANH), aminopyrine N-demethylase (ADM) activities were quantitated by UV chromatography. The levels of mRNA expression of CYP1A1, CYP2C11, CYP2E1 and CYP3A1 were detected by semi-quantitative reverse transcripatase-polymerase chain reaction (RT-PCR).</p><p><b>RESULT</b>The cytochrome P450 content, NADPH-Cyt C reductase activities and erythromycin N-demethylase (ERD) activities were not affected. Aniline hydroxylase (ANH) activities in liver were decreased by up to35.1%; aminopyrine N-demethylase (ADM) activitiesin liver were increased by up to 42.4%. The mRNA expression of CYP1A1, CYP2C11 and CYP3A1 were found to be increased markedly.</p><p><b>CONCLUSION</b>A specific effect of ESH on liver microsomal cytochrome P450 isoenzyme in rats was observed in this investigation. ESH had various effects on liver microsomal cytochrome P450 isoenzyme.</p>

Biotransformation enzymes in Cunninghamella blakesleeana (NCIM-687).

Presence of higher enzyme levels of aminopyrine N-demethylase, aniline hydroxylase and 11-beta hydroxylase activities were observed in Cunninghamella blakesleeana grown in potato-dextrose medium for 96 h. The enzyme activity preferred NADPH as a cofactor and showed inhibition with CO, indicating cytochrome P450 mediated reactions. A significant increase in aniline hydroxylase enzyme activity was observed when mycelia incubated in incubation medium containing different inducers (viz. camphor, cholesterol, naphthalene, veratrole, phenobarbital, n -hexadecane and ethyl alcohol) when compared with mycelia incubated in same way but in absence of inducers. Cunninghamella blakesleeana (NCIM 687) have shown the ability to degrade cholesterol, camphor and naphthalene when 96 h grown mycelia incubated in incubation medium containing these organic compounds.

Inhibition of drug metabolizing enzymes (cytochrome P450) in vitro as well as in vivo by Phyllanthus amarus SCHUM & THONN.

An alcoholic extract of Phyllanthus amarus (P. amarus) was found to inhibit cytochrome P450 (P450) enzymes both in vivo as well as in vitro. This was studied using specific resorufin derivatives, as substrate for isoenzymes in the P450 super family. Concentration needed for 50% inhibition of 7-ethoxyresorufin-O-deethylase (EROD), CYP1A1 was 4.6 microg/ml while concentration needed for 7-methoxyresorufin-O-demethylase (MROD) CYP1A2 was 7.725 microg/ml and 7-pentoxyresorufin-O-depentylase (PROD), CYP2B1/2 was found to be 4.18 microg/ml indicating that the extract inhibited the P450 enzymes at very low concentration. Extract also inhibited the activity of aniline hydroxylase (an indicator of CYP 2E1 activity, IC(50) 50 microg/ml) and aminopyrine demethylase (an indicator of CYP 1A, 2A 2B, 2D and 3A activity, IC(50) >1000 microg/ml). Oral administration of the extract was also found to reduce the elevated P450 enzyme activities produced by phenobarbitone by 50% at 250 mg/kg body weight. The implication of these results on the inhibition of carcinogenesis produced by the extract is discussed.

Chlorzoxazone metabolism is increased in fasted Sprague-Dawley rats.

Earlier data showed that men fasted for 38 h had a reduced rate of chlorzoxazone metabolism, suggesting a decreased level of cytochrome P450 2E1 (CYP2E1). In contrast, the level of CYP2E1 in fasted rats had been shown to be elevated. In this study, we have investigated whether chlorzoxazone metabolism in fasted rats was changed by determining the pharmacokinetics of chlorzoxazone and its metabolite, 6-hydroxychlorzoxazone (6-OHCZ), as a CYP2E1 probe, and by measuring liver CYP2E1 using immunoblot techniques. Chlorzoxazone was administered by gavage (50 mg kg(-1)) or intravenously (25 mg kg(-1)) to control (nine for oral and three for intravenous) and 24 h-fasted (nine for oral and four for intravenous) male Sprague-Dawley rats. Following sampling of blood through a jugular vein cannula, chlorzoxazone and 6-OHCZ plasma concentrations were measured by HPLC with UV detection. Pharmacokinetic parameters for chlorzoxazone and 6-OHCZ in each treatment group were determined by model fitting and non-compartmental analysis. In parallel with the increased liver CYP2E1 level, the elimination of chlorzoxazone and 6-OHCZ was significantly increased in fasted rats in the oral and the intravenous study. A multiple analysis of variance covariance analysis and a multiple regression analysis revealed a significant correlation between 1/t(1/2) and CYP2E1 level and aniline hydroxylase activity. However, the correlation between 1/t(1/2) and pentoxyresorufin O-dealkylase, ethoxyresorufin O-dealkylase and erythromycin N-demethylase was not significant. Therefore the contribution of other P450s to chlorzoxazone metabolism seemed to be minor in the concentration range that we tested. In conclusion, fasting rats for 24 h caused a measurable induction of CYP2E1, which produced a significant increase in the rate of chlorzoxazone metabolism and elimination.

Differential effects of diabetes on CYP2E1 and CYP2B4 proteins and associated drug metabolizing enzyme activities in rabbit liver.

The effects of diabetes on cytochrome P450 (CYP)-dependent drug metabolizing enzymes are yet to be clarified. The most widely used animals in these studies have been rats, and information on the effects of diabetes on rabbit liver drug metabolizing enzymes have been unavailable until now. In this study, for the first time, a significant induction of liver CYP2E1 is demonstrated via immunoblot analysis in alloxan-induced rabbits. The CYP2E1 content of diabetic microsomes was highly correlated with the activities of liver aniline 4-hydroxylase (r=0.82, p<0.05), and p-nitrophenol hydroxylase (r=0.86, p<0.01), and diabetes increased the activities of the enzymes associated with CYP2E1. The activities of aniline 4-hydroxylase and p-nitrophenol hydroxylase were significantly increased by 1.7 and 1.8-fold, respectively compared to those of control rabbits. In marked contrast, diabetes had no effect on the protein levels of CYP2B4 as determined by immunoblotting and on benzphetamine N-demethylase activity, which is known to be specifically metabolized by CYP2B4 in rabbit liver. The present study demonstrates that diabetes increases the activities of CYP2E1 and associated enzymes but does not change the activity levels of CYP2B4 and associated enzymes in diabetic rabbits. These findings are in contrast to those of mice, hamsters and rats, and that suggest the presence of species-dependent responses of CYP-dependent drug metabolizing enzymes to diabetes.

The roles of Kupffer cells in hepatic dysfunction induced by ischemia/reperfusion in rats.

This study examined the role of Kupffer cells in altering the hepatic secretory and microsomal function during ischemia and reperfusion (Is/Rp). Rats were subjected to 60 min of hepatic ischemia, followed by 1 and 5 h of reperfusion. Gadolinium chloride (GdCl3, 7.5 mg/kg body weight, intravenously) was used to inactivate the Kupffer cells 1 day prior to ischemia. Is/Rp markedly increased the serum aminotransferase level and the extent of lipid peroxidation. GdCl3 significantly attenuated these increases. Is/Rp markedly decreased the bile flow and cholate output, and GdCl3 restored their secretion. The cytochrome P450 content was decreased by Is/Rp. However, these decreases were not prevented by GdCl3. The aminopyrine N-demethylase activity was decreased by Is/Rp, while the aniline p-hydroxylase activity was increased. GdCl3 prevented the increase in the aniline p-hydroxylase activity. Overall, Is/Rp diminishes the hepatic secretory and microsomal drug-metabolizing functions, and Kupffer cells are involved in this hepatobiliary dysfunction.

Influence of cigarette smoke on the L-ascorbic acid metabolism and the activities of drug-metabolizing enzyme in rats.

This study clarified the influence of cigarette smoke on the L-ascorbic acid (AsA) metabolism and the activities of drug-metabolizing enzyme in rats. The test rats (group T) were exposed to weak sidestream smoke from cigarettes for 2 h, everyday for 57 days. AsA concentration in the tissues and excreted amount of AsA in urine of group T tended to be higher than those of control group (group C). The plasma AsA concentration and the activities of aniline hydroxylase and 7-ethoxycoumarin O-deethylase of group T were significantly higher than those of group C. There was no significant difference in the activity of UDP glucuronosyltransferase or in the liver cytochrome P-450 content between these two groups.

Marek's disease vaccination, with turkey herpesvirus, and enrofloxacin modulate the activities of hepatic microsomal enzymes in broiler chickens.

Chickens were vaccinated against Marek's disease intramuscularly at one day of age. Enrofloxacin was given ad libitum in the drinking water at concentrations of 50, 100 and 250 mg/L from 8 days to 13 days of age when the animals were killed and the activities of cytochrome P-450 enzymes in the liver were measured. Vaccinated non-treated chickens served as a positive control. A negative control group was neither vaccinated nor treated. Vaccination decreased the activity of aniline hydroxylase and ethylmorphine N-demethylase in the positive control group. Subsequent application of enrofloxacin in the lowest concentration (50 mg/L) decreased, while that given at the highest level (250 mg/L) significantly increased the activity of the same microsomal enzymes. Relative liver weights and concentrations of proteins in 9000 x g supernatant were not affected by vaccination or treatment.

Anti-hepatotoxic effects of Rosa rugosa root and its compound, rosamultin, in rats intoxicated with bromobenzene.

The effects of a methanol extract of Rosa rugosa root and its triterpenoid glycoside, rosamultin, on hepatic lipid peroxidation and drug-metabolizing enzymes were investigated in rats treated with bromobenzene. The methanol extract of R. rugosa root reduced the activities of aminopyrine N-demethylase and aniline hydroxylase, which had been increased by bromobenzene, but rosamultin did not affect the activities of the two enzymes. Both the methanol extract and rosamultin restored the activity of epoxide hydrolase, which had also been decreased by bromobenzene. Hepatic glutathione concentrations were lowered and hepatic lipid peroxides were increased in rats intoxicated with bromobenzene. The hepatic lipid peroxidation induced by bromobenzene was prevented with the methanol extract and rosamultin. However, the decrease in glutathione was not altered by the methanol extract of R. rugosa. These results suggest that the extract of R. rugosa and its compound, rosamultin, may protect against bromobenzene-induced hepatotoxicity through, at least in part, enhanced activity of epoxide hydrolase. Antioxidant properties may contribute to the protection of R. rugosa against bromobenzene-induced hepatotoxicity.