Neuroprotective effect of Decalepis hamiltonii roots against ethanol-induced oxidative stress

The neuroprotective potential of the aqueous extract of the roots of Decalepis hamiltonii (D. hamiltonii root aqueous extract-DHRAE) was studied against ethanol-induced oxidative stress in the rat brain. Ethanol, single dose (5 g/kg body weight), induced oxidative stress in the rat brain which was evident from the increased lipid peroxidation and protein carbonylation, reduced glutathione, and suppressed activities of antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione-S-transferase. Pretreatment of rats with multiple doses of DHRAE, 50 and 100 mg/kg b.w., for 7 consecutive days significantly prevented the ethanol-induced oxidative stress. DHRAE, as such, boosted the antioxidant status of the rat brain. The neuroprotective potential of DHRAE can be attributed to the known antioxidant constituents or its interaction with antioxidant response elements (AREs) which needs to be ascertained.     

Effect of amaranth seeds in diet on oxidative status in plasma and selected tissues of high fructose-fed rats

The aim of this study was to assess the influence of amaranth seeds in different doses, under conditions of oxidative stress induced by dietary fructose, on antioxidant status of selected rat tissues, erythrocytes and plasma. Fructose administration caused oxidative stress that was manifested by the increase in plasma malondialdehyde and by the decrease in the enzymatic antioxidant activity. Co-administration of amaranth seeds influenced the oxidative stress, as was evidenced by decreasing malondialdehyde in plasma and changing the activities of antioxidant enzymes (erythrocyte superoxide dismutase, catalase, and plasma glutathione peroxidase). Our findings demonstrate that amaranth seeds can act as a moderate protective agent against fructose-induced changes. Our results suggest that the antioxidative system of plasma, heart and lungs is more efficient when amaranth seeds are present in the diet.     

Protective effect of dietary ginger on antioxidant enzymes and oxidative damage in experimental diabetic rat tissues

The role of oxidative stress has been reported in various diabetic complications. This study was undertaken to evaluate the protective effect of ginger, a medicinal plant, on the tissue antioxidant defence system and lipid peroxidative status in streptozotocin-induced diabetic rats. An increased reactive oxygen species and insufficient antioxidant activity are associated with diabetes mellitus, which is mainly responsible for diabetic pathogenesis. The role of ginger as antioxidant markers of liver and kidney were investigated. The antioxidant effect of the ginger was compared with glibenclamide, a well-known hypoglycaemic drug. The diabetic rats exhibited lower activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) and reduced glutathione (GSH) content and higher level of malondialdehyde (MDA) in hepatic and renal tissues as compared with normal rats. The activities of all parameters were found to be increased, except MDA in ginger-treated diabetic rats, in hepatic and renal tissues. Ginger supplementation, for 30 days to diabetic rats, resulted in significant dose-dependent hypoglycaemic and antioxidant activities. These findings suggest that ginger treatment exerts a therapeutic protective effect in diabetes by decreasing oxidative stress, and hepatic and renal damage.     

Antioxidative characteristics of aqueous and ethanol extracts of glossy privet fruit

Non-enzymatic antioxidant activities of aqueous extract, 50% ethanol extract and 75% ethanol extract of glossy privet fruit were examined. Aqueous and ethanol extracts contained various concentrations of phenolic acids, flavonoids, oleanolic acid and ursolic acid. Each extract scavenged superoxide anion, hydroxyl radical and nitric oxide (P < 0.05) in a concentration-dependent manner and the effect of 75% ethanol extract was significantly greater than other extracts (P < 0.05). Each extract showed a concentration-dependent effect on chelating effect, xanthine oxidase inhibition activity and reducing power (P < 0.05). Compared with controls, each extract significantly decreased malondialdehyde formation in low density lipoprotein (LDL) and 8-epi-PGF_2α formation in plasma (P < 0.05). Aqueous extract exerted a greater effect than ethanol extract on increasing catalase and glutathione peroxidase activities in plasma (P < 0.05). These data suggest that using glossy privet fruit extracts may enhance lipid stability in food systems, and provide antioxidative protection for LDL and plasma.     

Alleviation of plasma,erythrocyte and liver lipidemic-oxidative stress by thymoquinone and limonene in atherogenic suspension fed rats

In the present study, the antioxidant efficacies of thymoquinone (TQ) and limonene (LMN), two main constituents of Nigella sativa seeds, were investigated in relation to plasma, erythrocyte and liver oxidative abnormalities in hyperlipidemic Wistar albino rats. Pretreatment with 10 mg TQ or 200 mg LMN in atherogenic suspension fed rats, effectively reduced the plasma lipid peroxidation markers, conjugated diene, lipid hydroperoxide, malondialdehyde, and replenished the plasma antioxidant capacity by increasing its ferric reducing ability and 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid quenching to near normal levels and modulating the levels of reduced glutathione, enzymatic antioxidants superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, and erythrocyte membrane-linked ATPases to normalcy. These results demonstrate that radical scavenging/antiperoxidative efficacies of TQ were greater than LMN. Thus, these compounds, especially TQ, play an important and useful role in the preservation of plasma antioxidant status, cellular membrane structure and function of tissues, and may be used as chemopreventative food additives in the prooxidant state related disorders.     

Hydroxytyrosyl acetate contributes to the protective effects against oxidative stress of virgin olive oil

The effects of virgin olive oil phenols, hydroxytyrosyl acetate (HTy-Ac) and hydroxytyrosol (HTy), on cell integrity and steady-state values of cellular redox status were assessed in HepG2 cells, as well as their potential protective effects against oxidative stress induced by tert-butyl hydroperoxide (t-BOOH). Direct treatment for 20 h with 0.5-10 μM HTy or HTy-Ac reduced ROS generation and increased glutathione peroxidase activity at the higher concentrations. Furthermore, after t-BOOH exposure, pretreatment with HTy-Ac and HTy for 2 or 20 h counteracted cell viability damage from 1 μM, counterbalanced reduced glutathione levels from 0.5 μM, protected against lipid peroxidation from 0.5 μM, decreased ROS generation from 1 μM as well as antioxidant enzyme activities from 1 μM. All these changes were statistically significant.HTy-Ac presents antioxidative stress protective effects at physiological concentrations similar to or even slightly higher than that of HTy, thus contributing to the protective role of virgin olive oil.     

Suppressive effect of ethyl acetate extract of Teucrium polium on cellular oxidative damages and apoptosis induced by 2-deoxy-d-ribose: Role of de novo synthesis of glutathione

The effect of ethyl acetate (EtOAc) extract of Teucrium polium on 2-deoxy-d-ribose (dRib)-induced oxidative stress and apoptosis in erythroleukemic K562 cells was investigated. K562 cells exposed to dRib (50 mM) exhibited abnormal properties such as overproduction of reactive oxygen species, lipid peroxidation, glutathione (GSH) depletion and biochemical features of apoptosis. Treatment with EtOAc extract (25 and 50 μg/ml) reduced oxidative stress and apoptosis among the dRib-treated K562 cells. To disclose the mode of action, the effect of the extract on the cellular GSH and its synthesis by γ-glutamylcysteine synthetase (γ-GCS), a key rate-limiting enzyme of the GSH synthetic pathway, were evaluated. The results demonstrated that the antioxidant property of EtOAc extract mainly results from increasing the level of cellular GSH by inducing the activity of γ-GCS. It can be concluded that the EtOAc extract of T. polium prevents dRib-induced oxidative stress and apoptosis mostly through antioxidative mechanisms.     

Dietary supplementation of ferulic acid and ferulic acid ethyl ester induces quinone reductase and glutathione-S-transferase in rats

Ferulic acid ethyl ester (FAEE) and ferulic acid (FA) were fed to rats to determine in vivo efficacy in elevating selected phase II enzyme activities and antioxidant capacity. Male Sprague–Dawley rats were fed the AIN-93M control diet, or the control diet supplemented with 1% FA, 1% FAEE, or 0.1% FAEE for 2 weeks. Quinone reductase (QR), glutathione-S-transferase (GST), thioredoxin reductase (TxR) activities, and oxidised and reduced glutathione were determined for brain, lung, liver, kidney, intestine and colon tissues. Both FA and FAEE (1%) supplementation increased QR and GST specific activities in kidney and colon tissues by 23–38% relative to the control diet. FAEE (1%) supplementation also induced QR specific activity, by 1.46- and 1.27-fold over the control diet, in intestinal and lung tissue of animals, whereas FA did not. No effect of diet was observed on liver cytochrome P450-1A1 activity. These results demonstrate that dietary FA and FAEE induce QR activity in the colon, small intestine, lung, and kidney, and improve glutathione antioxidant status in the colon and intestine. Therefore, dietary FA and FAEE may elevate defences to oxidative- and xenobiotic-induced stress in vivo.     

Lipid peroxidation,protein oxidant and antioxidant status of muscle,intestine and hepatopancreas for juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of myo-inositol

Lipid peroxidation, protein oxidant and antioxidant status of muscle, intestine and hepatopancreas in juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of myo-inositol (MI) (163.5, 232.7, 384.2, 535.8, 687.3, 838.8 and 990.3 mg/kg diet) for 60 days were investigated. Total tissue malondialdehyde (MDA) and protein carbonyl (PC) content showed a downward trend to a point (P < 0.05). Conversely, total tissue anti-hydroxyl radical (AHR), catalase (CAT), glutathione-S-transferase (GST), glutathione peroxidase (GPx), glutathione reducase (GR) activities and glutathione (GSH) content were generally higher in MI-supplemented diets than MI-unsupplemented diet (P < 0.05). Muscle and intestinal superoxide dismutase (SOD), and intestinal anti-superoxide anion (ASA) were increased by MI supplementation (P < 0.05), whereas these parameters in the other tissue showed no alterations (P > 0.05). These results indicated that antioxidant status was improved, and lipid peroxidation and protein oxidant were depressed in muscle, intestine and hepatopancreas by MI.     

An active peptide purified from gastrointestinal enzyme hydrolysate of Pacific cod skin gelatin attenuates angiotensin-1 converting enzyme (ACE) activity and cellular oxidative stress

Seafood processing by-product, Pacific cod (Gadus macrocephalus) skin, was utilised to purify an active peptide with ACE inhibitory and antioxidant activities. Gelatin was extracted from the skin and it was hydrolysed with gastrointestinal endopeptidases (pepsin, trypsin and α-chymotrypsin). Assay-guided purification of the hydrolysate resulted in an active peptide, Leu-Leu-Met-Leu-Asp-Asn-Asp-Leu-Pro-Pro (1301 Da). The peptide showed potent non-competitive ACE inhibition (IC₅₀ = 35.7 μM) and effectively protects cellular macromolecules from reactive oxygen species (ROS) mediated damage. The peptide significantly reduced the oxidation levels of membrane lipids, proteins and DNA in RAW264.7 cells by effectively scavenging the intracellular ROS. Moreover, it was found that the peptide treatment upregulated the m-RNA expression of cellular antioxidative enzymes (superoxide dismutase, glutathione and catalase) and thereby enhanced the intracellular antioxidant mechanisms. These findings suggest that Pacific cod skin could be effectively bioconverted to produce a bioactive peptide, which could be used as a functional food ingredient to control ACE activity and oxidative stress.     

Long-term supplementation of high pigmented rice bran oil (Oryza sativa L.) on amelioration of oxidative stress and histological changes in streptozotocin-induced diabetic rats fed a high fat diet; Riceberry bran oil

Diabetes is a serious health problem. Searching for alternative natural antioxidants is considered important strategy to manage diabetes. This study evaluated the effect of Riceberry bran oil (RBBO) supplementation on oxidative stress and organ histology in streptozotocin-induced diabetic rats fed a high fat (HF) diet. Adult male Sprague-Dawley rats with hyperglycemia were divided into four groups: DM group fed a HF diet alone; DMRL group fed a HF diet and 5% RBBO; DMRM group fed a HF diet and 7.5% RBBO; DMRH group fed a HF diet and 15% RBBO. Normal rats were used as normal control and were divided into NC and NR group fed a normal diet containing either 5% corn oil or 5% RBBO, respectively. After 12 weeks, RBBO significantly decreased malondialdehyde and restored superoxide dismutase, catalase, glutathione peroxidase, coenzyme Q₁₀ and ORAC levels in diabetic rats. RBBO additionally improved the regenerative changes of the pancreas, kidneys, heart and liver. These findings indicate that pigmented RBBO could provide beneficial effect on diabetes by decreasing oxidative stress and recovering organ histology.     

Phycobiliproteins or C-phycocyanin of Arthrospira (Spirulina) maxima protect against HgCl2-caused oxidative stress and renal damage

Our objective was to determine if the phycobiliproteins of Arthrospira (Spirulina) maxima protect renal cells against mercury-caused oxidative stress and cellular damage in the kidney. We used 40 male mice that were assigned into eight groups: (1) a control group that received 100 mM phosphate buffer (PB) ig and 0.9% saline ip, (2) PB + HgCl₂ (5 mg/kg ip), (3) PB plus phycobiliproteins (100 mg/kg ig), (4) PB plus C-phycocyanin (100 mg/kg ig), and four groups receiving HgCl₂ + phycobiliproteins or C-phycocyanin (50, and 100 mg/kg ig). The left kidneys were used to determine lipid peroxidation, quantification of reactive oxygen species, and reduced glutathione and oxidised content. The right kidneys were processed for histology. The HgCl₂ caused oxidative stress and cellular damage. All doses of phycobiliproteins or C-phycocyanin prevented enhancement of oxidative markers and they protected against HgCl₂-caused cellular damage.     

The effects of moderately oxidised dietary oil with or without vitamin E supplementation on performance, nutrient digestibility, some blood traits, lipid peroxidation and antioxidant defence of male broilers

BACKGROUND: The experiment was conducted to determine the effects of dietary supplementation of oxidised oil with or without vitamin E on performance, nutrient digestibility, some blood traits, lipid peroxidation and antioxidant defence system of male broilers. RESULTS: The supplementation of oxidised oil with or without vitamin E to the grower diets did not significantly affect performance, the pH and viscosity values of excreta and nutrient digestibilities in male broilers. Oxidised oil supplementation slightly increased plasma triglyceride and cholesterol concentrations but did not alter plasma glucose concentration. Although malondialdehyde (MDA) and nitric oxide concentrations tended to be higher in the oxidised oil group, these increases were not significant. Birds fed the diet containing oxidised oil had significantly lower superoxide dismutase (SOD) activity. However, no differences were observed in glutathione peroxidase (GSH‐Px) activity and uric acid concentrations of broilers fed oxidised oil as compared to the control group. Dietary vitamin E supplementation decreased MDA concentration whereas increasing SOD activity, suggesting that vitamin E supplementation reduced susceptibility to lipid peroxidation. CONCLUSION: The results showed that a milder oxidative stress occurred by supplementation of moderately oxidised oil to the diet of broilers and vitamin E supplementation had been helpful in alleviating lipid peroxidation. Copyright © 2011 Society of Chemical Industry     

Piper species protect cardiac,hepatic and renal antioxidant status of atherogenic diet fed hamsters

Pre-clinical and clinical studies points to the use of antioxidants as an effective measure to reduce the progression of oxidative stress related disorders. The present study evaluate the effect of three Piper species (Piper guineense, Piper nigrum and Piper umbellatum) for the protection of cardiac, hepatic and renal antioxidant status of atherogenic diet fed hamsters. Hamsters were classified into eight groups: a normal control, atherogenic control and six other experimental groups (fed atherogenic diet supplemented with different doses of P. nigrum, P. guineense and P. umbellatum (1 and 0.25 g/kg) for 12 weeks. At the end of the feeding period the heart, liver and kidney from each group were analyzed for lipid profile and antioxidant enzymes activities. Atherogenic diet induced a significant (P < 0.001) increase in the lipid profile across the board and equally significantly altered the antioxidant enzyme activities. Supplementation with Piper species significantly inhibited the alteration effect of atherogenic diet on the lipid profile and antioxidant enzymes activities. The Piper extracts may possess an antioxidant protective role against atherogenic diet induced oxidative stress in cardiac, hepatic and renal tissues.     

Effects of different levels of trans fatty acids and oxidised lipids in diet on cholesterol and cholesterol oxidation products formation in rabbit

The objective was to assess the effects of trans fatty acids and oxidised lipids, present in dietary fat by-products used in feeds, on cholesterol and oxycholesterols in meat, liver and plasma of rabbits. A palm fatty acid distillate, before and after hydrogenation (trans fatty acid trial), and a sunflower–olive oil blend (70/30, v/v), before and after use in a commercial frying process (oxidised lipid trial), were used in experimental feeds (at 3%, w/w). High trans fatty acid and oxidised lipid diets caused significantly higher cholesterol and oxycholesterol levels in all tissues of rabbit (0.01 < p ? 0.05). The content of oxycholesterols in rabbit meat, liver and plasma obtained from trans fatty acid experiments varied from 9 to 34 μg/100 g, 24 to 61 μg/100 g and 60 to 138 μg/dl, respectively, from low to high levels. In the oxidised lipid experiments, content of oxycholesterols varied from 16 to 52 μg/100 g, 14 to 108 μg/100 g and 52 to 269 μg/dl in meat, liver and plasma, respectively. As a consequence, meat products from rabbits fed a diet containing higher levels of trans fatty acids or oxidised lipids may result in higher intakes of cholesterol and oxycholesterols by humans.     

Relative antioxidant and cytoprotective activities of common herbs

Many studies have been carried out on bioactivities of individual herbs, however, no collective study on their comparative antioxidant and cytoprotective activities against oxidative damage has been reported. We selected 17 common commercial herbs and studied their relative phenolic contents, antioxidant activities, and cytoprotective activities on gap–junction intercellular communication and antioxidative enzymes in vitro under the same conditions. Total polyphenol content ranged from 464 to 870 gallic acid equivalents (GAE) mg/100 g and total flavonoid content from 212 to 494 catechin equivalents (CE) mg/100 g. Among the samples, chamomile, rosehip, hawthorn, lemon verbena, and green tea contained relatively high total phenolics (769–844 mg GAE/100 g) and flavonoids (400–4 mg CE/100 g). Chamomile also showed the highest antioxidant activity with 960 mg/100 g of vitamin C equivalent (VCE), followed by hawthorn (929 mg VCE/100 g) and black tea (916 mg VCE/100 g). Total phenolic and total flavonoids showed a higher correlation with antioxidant activity. Most of herbs enhanced cell viability and showed protective effects against oxidative stress induced by hydrogen peroxide in Chinese hamster lung fibroblast (V79-4) cells. Furthermore, herbs used in this study showed higher protective effect on gap–junction intercellular communication (GJIC) as compared to gallic acid and catechin, and also enhanced activity of the antioxidative enzymes such as superoxide dismutase (SOD) and catalase (CAT) in a dose-dependent manner.     

Chinese bayberry fruit extract alleviates oxidative stress and prevents 1,2-dimethylhydrazine-induced aberrant crypt foci development in rat colon carcinogenesis

The effects of Chinese bayberry fruit extract (CBFE) ingestion on hepatic and colonic oxidative stress and 1,2-dimethylhydrazine (DMH)-induced intestinal aberrant crypt foci (ACF) development in rats were investigated. Rats were administered DMH (35 mg/kg body weight) and were supplemented with CBFE (50 or 500 mg/kg body weight every day) for 16 weeks. Results showed that DMH consumption induced intestinal ACF development and adenoma or adenocarcinoma formation, which were significantly reduced with CBFE supplement. The CBFE treatments increased reduced glutathione levels and activities of superoxide dismutase, catalase and glutathione reductase, in both hepatic and colonic tissues; however, the activities of glutathione-S-transferase and glutathione peroxidase were inhibited. These results indicate that CBFE, rich in phenolic compounds, effectively inhibits DMH-induced ACF and colonic tumour development by alleviating oxidative stress.     

Effect of the Lycium barbarum polysaccharides administration on blood lipid metabolism and oxidative stress of mice fed high-fat diet in vivo

Epidemiological and experimental studies have suggested that high dietary fat intake of mice is associated with many physically degenerative diseases. Since oxidative stress and abnormal lipid metabolism have been speculated to be critical mechanisms underlying degenerative diseases, we hypothesized that a high-fat (HF) diet might induce oxidative stress or lipid oxidation and subsequently contribute to the high risk of some diseases such as cardiovascular and cerebrovascular ones. To test this hypothesis, male kunming mice were placed on either a HF diet or a normal laboratory diet for 30 consecutive days. This investigation demonstrated that blood fat [low density lipoprotein (LDL), total cholesterol (TC), triacylglycerols (TAG), high density lipoprotein (HDL)], blood sugar (blood glucose and liver glycogen) and oxidative stress (activities of antioxidant enzymes and levels of non-enzymic antioxidants) of mice fed high-fat diet (group II) were significantly increased or decreased (P < 0.05, P < 0.01) when compared with the control group (I). The present study revealed that HF diet induced oxidative stress and provided novel evidence regarding the link between high dietary fat and increased risk of degenerative diseases. The administration of Lycium barbarum polysaccharides did not show any effect on the body weight of the experimental mice, but significantly decreased the levels of LDL, TC, TAG, blood glucose and thiobarbituric acid reactive substances (TBARS) or increased the activities of antioxidant enzymes (P < 0.05, P < 0.01) when compared with mice in HF group (II). These findings were further supported by significantly increased non-enzymic antioxidants levels (P < 0.05, P < 0.01), suggesting that L. barbarum polysaccharides showed a noticeable inhibition against lipid oxidation induced by free radicals caused by HF diet intake (groups III, IV, V) on the basis of their antioxidant activities.     

Effects of diet enriched with restructured meats,containing Himanthalia elongata, on hypercholesterolaemic induction,CYP7A1 expression and antioxidant enzyme activity and expression in growing rats

Meat and pork consumptions are very high in Spain. Seaweeds are rich in fibre, minerals, and bioactive substances. Due to the growing demand for healthier meats, this work studied the effect of diets containing restructured pork (RP) enriched with Himanthalia elongata (Sea Spaghetti) on: (1) cholesterolaemia; (2) liver cytochrome P450 7A1 (CYP7A1) expression; (3) liver antioxidant enzyme activities and gene expression; (4) the liver antioxidant substrate concentrations. Four groups of 10 Wistar rats each were fed a mix of 85% AIN-93 M rodent diet and 15% freeze-dried RM for 35 days. The control group (C) consumed control RP; the Sea Spaghetti (SS) group, RP with 5% Sea Spaghetti. Animals on added cholesterol diets (CholC and CholSS) consumed their basal C and SS diets enriched with cholesterol and cholic acid as hypercholesterolaemic agent. Food intake was significantly affected by the alga × cholesterol interaction and by dietary cholesterol (both p < 0.001). Plasma cholesterol was significantly affected by the cholesterol × alga interaction (p < 0.05). CholC rats showed significantly higher plasma cholesterol (p < 0.001) than did their C counterparts, whilst serum cholesterol of CholSS was significantly lower (p < 0.05) than that of CholC. The glutathione peroxide (GSSG) concentrations and all mRNA expressions were significantly affected by the cholesterol × alga interaction (at least p < 0.05). SS vs C group showed significant (at least p < 0.05) increases in superoxide dismutase (Mn-SOD and Cu,Zn-SOD), glutathione peroxidase (GPx) and decrease of glutathione reductase (GR) expressions, and increased GR activity, GSSG and the redox index. CholSS vs CholC showed significant (at least p < 0.05) increases of CYP7A1, GR and Cu,Zn-SOD expression but decreases in catalase, Mn-SOD and GPx expression, and increase of GR activity. In conclusion, Sea Spaghetti could be widely used in RP design. Its addition to non-cholesterol enriched RP diet reduced oxidation mechanisms. SS-RP partially blocked the effect of the hypercholesterolaemic agent, giving rise to a new balance of the antioxidant enzyme expression.     

Protective effects of the crude extracts from yam (Dioscorea alata) peel on tert-butylhydroperoxide-induced oxidative stress in mouse liver cells

Researchers have shown that yam extracts contain antioxidative activity; however, there are few reports regarding the antioxidant activities of yam peel. The effects of water and 50% ethanolic extracts from Darsan yam (Dioscorea alata) peel on the oxidative status of tert-butylhydroperoxide (t-BHP)-treated mouse Hepa 1–6 and FL83B liver cell lines were investigated. The cytosols were analysed for H₂O₂ and malondialdehyde (MDA) levels and antioxidative enzymes activities, including superoxide dismutase, glutathione peroxidase (GPx) and catalase activities. Both water and 50% ethanolic extracts from yam peel did not affect cellular MDA level in t-BHP-treated cells, but they altered the level of H₂O₂. Water extract from yam peel amplified the t-BHP-induced cytotoxicity in Hepa 1–6 whilst the ethanolic extract showed protection in FL83B cells. GPx activity might play an important role in the protective effect associated with t-BHP-induced oxidative stress.