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PubMed2005

Cap1p is involved in multiple pathways of oxidative stress response in Candida albicans.

Cap1p, a transcription factor in Candida albicans, is thought to participate in oxidative stress tolerance, but the pathways involved are still unclear. The study was designed to reveal the possible pathways by examining changes in the transcription profile after H2O2 treatment with both the cap1-deleted strain CJD21 and its parental strain CAI4 using microarray analysis. Of the identified 89 genes differentially expressed in CAI4 after exposure to H2O2, 76 genes were in a Cap1p-dependent expression pattern. We have shown that Cap1p is involved in the oxidative stress response in C. albicans via multiple pathways, including the cellular antioxidant defense system (e.g., thioredoxin reductase, glutathione reductase, glutathione S-transferase), carbohydrate metabolism and energy metabolism (e.g., glucose-6-phosphate dehydrogenase, transaldolase, glyoxalase I, NADH-dependent flavin oxidoreductase), protein degradation (e.g., 26S proteasome regulatory subunit, ubiquitin-specific protease), ATP-dependent RNA helicase (e.g., DEAD box protein ATP-dependent RNA helicase), and resistance pathways (e.g., multidrug resistance protein, ABC transporter essential for cadmium resistance). Real-time reverse transcription-PCR analysis further confirmed the results of microarray. Collectively, this study provides new insight into the biological functions of Cap1p in oxidative stress response.

Basic-Leucine Zipper Transcription Factors↗

PubMed2003

Protective effect of adenosine in rat model of Parkinson's disease: neurobehavioral and neurochemical evidences.

Normal cellular metabolism produces oxidants which are neutralized within the cell by antioxidant enzymes and other antioxidants. An imbalance between oxidant and antioxidant has been postulated to lead the degeneration of dopaminergic neurons in Parkinson's disease. In this study, we examined whether adenosine, an antioxidant, can prevent or slowdown neuronal injury in 6-hydroxydopamine (6-OHDA) model of Parkinsonism. Rats were treated with adenosine (500, 250, 125 mg/kg b.wt.) once before surgery and five times after surgery (1 h interval). 2 microl 6-OHDA (12.5 microg in 0.2% ascorbic acid in normal saline) was infused in the right striatum. Two weeks after 6-OHDA infused rats were tested for neurobehavioral activity and sacrificed after 3 weeks of 6-OHDA infusion, for the estimation of glutathione peroxidase, glutathione-S-transferase, glutathione reductase, glutathione content, lipid peroxidation and dopamine and its metabolites. Adenosine was found to be successful in up-regulating the antioxidant status, lowering the dopamine loss and functional recovery returned close to the baseline dose. This study revealed that adenosine, which is an essential part of our body, might be helpful in slowing down the progression of neurodegeneration in Parkinsonism.

Adenosine↗

PubMed2006

Attenuation by Nardostachys jatamansi of 6-hydroxydopamine-induced parkinsonism in rats: behavioral, neurochemical, and immunohistochemical studies.

Parkinson's disease (PD) is one of the commonest neurodegenerative diseases, and oxidative stress has been evidenced to play a vital role in its causation. In the present study, we evaluated whether ethanolic extract of Nardostachys jatamansi roots (ENj), an antioxidant and enhancer of biogenic amines, can slow the neuronal injury in a 6-OHDA-rat model of Parkinson's. Rats were treated with 200, 400, and 600 mg/kg body weight of ENj for 3 weeks. On day 21, 2 microl of 6-OHDA (12 microg in 0.01% in ascorbic acid-saline) was infused into the right striatum, while the sham-operated group received 2 microl of vehicle. Three weeks after the 6-OHDA injection, the rats were tested for neurobehavioural activity and were sacrificed after 6 weeks for the estimation of lipid peroxidation, reduced glutathione content, the activities of glutathione-S-transferase, glutathione reductase, glutathione peroxidase, superoxide dismutase and catalase, quantification of catecholamines, dopaminergic D2 receptor binding and tyrosine hydroxylase expression. The increase in drug-induced rotations and deficits in locomotor activity and muscular coordination due to 6-OHDA injections were significantly and dose-dependently restored by ENj. Lesioning was followed by an increased lipid peroxidation and significant depletion of reduced glutathione content in the substantia nigra, which was prevented with ENj pretreatment. The activities of glutathione-dependent enzymes, catalase and superoxide dismutase in striatum, which were reduced significantly by lesioning, were dose-dependently restored by ENj. A significant decrease in the level of dopamine and its metabolites and an increase in the number of dopaminergic D2 receptors in striatum were observed after 6-OHDA injection, and both were significantly recovered following ENj treatment. All of these results were exhibited by an increased density of tyrosine hydroxylase immunoreactive (TH-IR) fibers in the ipsilateral striatum of the lesioned rats following treatment with ENj; 6-OHDA injection had induced almost a complete loss of TH-IR fibers. This study indicates that the extract of Jatamansi might be helpful in attenuating Parkinsonism.

Animals↗

PubMed2005

Upregulation of endogenous antioxidants and phase 2 enzymes by the red wine polyphenol, resveratrol in cultured aortic smooth muscle cells leads to cytoprotection against oxidative and electrophilic stress.

Resveratrol (3,4',5-trihydroxystilbene), a polyphenolic compound found in mulberries, grapes and red wine has been demonstrated to be capable of protecting against oxidative cardiovascular pathophysiology. However, the underlying cellular and biochemical mechanisms remain to be elucidated. This study was undertaken to determine if resveratrol could upregulate endogenous antioxidants and phase 2 enzymes in cultured aortic smooth muscle cells (ASMCs), and if such increased cellular defenses could provide protection against oxidative and electrophilic vascular cell injury. Incubation of rat ASMCs with resveratrol at low micromolar concentrations resulted in a significant induction of a scope of cellular antioxidants and phase 2 enzymes in a concentration- and/or time-dependent fashion. These cytoprotective factors include superoxide dismutase, catalase, glutathione, glutathione reductase, glutathione peroxidase, glutathione S-transferase (GST), and NAD(P)H:quinone oxidoreductase-1 (NOQ1). Notably, induction of catalase, GST, and NOQ1 was most remarkable among the above resveratrol-inducible antioxidants and phase 2 enzymes. Moreover, resveratrol treatment also significantly increased the mRNA expression of catalase, GSTA1, and NQO1 in a time-dependent manner. Pretreatment of ASMCs with resveratrol afforded a remarkable protection against xanthine oxidase (XO)/xanthine- or 4-hydroxy-2-nonenal-induced cytotoxicity, as assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) reduction assay. Resveratrol pretreatment also led to a marked reduction in intracellular accumulation of reactive oxygen species in ASMCs after incubation with XO/xanthine. Taken together, this study demonstrates that a scope of key endogenous antioxidants and phase 2 enzymes in cultured ASMCs can be upregulated by resveratrol at low micromolar concentrations, and that such chemically-elevated cellular defenses rendered cells increased resistance to oxidative and electrophilic stress. The results of this study thus suggested a new mechanism, which might contribute to the cardiovascular protective effects of resveratrol.

Aldehydes↗

PubMed1996

Effect of cis-unsaturated fatty acids on cellular oxidant stress in macrophage tumor (AK-5) cells in vitro.

Cis-unsaturated fatty acids (c-UFAs) induced decreased survival of macrophage tumor (AK-5) cells in vitro. The cytotoxic action of c-UfAs was associated with an increase in free radical generation and lipid peroxidation process. In addition, exposure of AK-5 cells to various c-UFAs for a short period (1 h) decreased the cellular concentrations of anti-oxidants: superoxide dismutase (SOD), catalase, glutathione peroxidase, glutathione reductase, glutathione and vitamin E. However, prolonged (24 h) exposure of AK-5 cells to c-UFAs enhanced the levels of SOD with little or no change in the concentrations of catalase, glutathione peroxidase and glutathione reductase. These results indicate that c-UFAs can enhance free radical generation and lower the concentrations of various anti-oxidants in the tumor cells which may explain the cytotoxic action of c-UFAs.

Animals↗

PubMed2002

Comparison between the antioxidant status of terrestrial and diving mammals.

Many diving mammals are known for their ability to deal with nitrogen supersaturation and to tolerate apnea for extended periods. They are all characterized by high oxygen-carrying capacity in blood together with high oxygen storage in their muscle mass due to large myoglobin concentrations. The above properties theoretically also imply a high tissue antioxidant defenses (AD) to counteract reactive oxygen species (ROS) generation associated with the rapid transition from apnea to reoxygenation. Different enzymatic (superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, and glutathione S-transferase), and non-enzymatic (levels of glutathione) AD as well as cellular damage (thiobarbituric acid-reactive substances contents, as a measure of lipoperoxidation) were measured in blood samples obtained from anesthetized animals, and also in blood obtained from recently dead diving mammals, and compared to some terrestrial mammals (n=5 in both groups). The results confirmed that diving mammals have, in general, higher antioxidant status compared to non-diving mammals. Apparently, to avoid exposure of tissues to changing high oxygen levels, and therefore to avoid an oxidative stress condition related to antioxidant consumption and increased ROS generation, diving mammals possess constitutive high levels of antioxidants in tissues. These data are in agreement with short-term AD adaptations related to torpor and to animals that experience large daily changes in oxygen consumption. These data are similar to the long-term adaptations of animals that undergo hibernation, estivation, freezing-thawing and dehydration-rehydration processes. In summary, animals that routinely face high changes in oxygen availability and/or consumption seem to show a general strategy to prevent oxidative damage by having either appropriate high constitutive AD and/or the ability to undergo arrested states, where depressed metabolic rates minimize the oxidative challenge.

Animals↗

PubMed1998

Dietary monounsaturated n-3 and n-6 long-chain polyunsaturated fatty acids affect cellular antioxidant defense system in rats with experimental ulcerative colitis induced by trinitrobenzene sulfonic acid.

The intrarectal administration of trinitrobenzene sulfonic acid in rats induces ulcerative colitis, which results in histological alterations of colonic mucosa, severe modification of the cellular antioxidant defense system, and enhanced production of inflammatory eicosanoids. This study evaluated the influence of different dietary fatty acids, i.e., monounsaturated, n-3, and n-3 + n-6 polyunsaturated fatty acids, on the recovery of the colonic mucosa histological pattern, the cellular antioxidant defense system of colon, and PGE2 and LTB4 colonic mucosa contents in a model of ulcerative colitis induced by intrarectal administration of trinitrobenzene sulfonic acid. Administration of dietary n-3 polyunsaturated fatty acids led to a minimum stenosis score, a higher histological recovery, lower colon alkaline phosphatase and gamma-glutamyltranspeptidase activities, and lower mucosal levels of PGE2 and LTB4 compared with the other two experimental groups. However, glutathione transferase, glutathione reductase, glutathione peroxidase, and catalase activities were lower in the group treated with n-3 polyunsaturated fatty acids than in the groups fed with either the monounsaturated or the n-6 + n-3 polyunsaturated enriched diet. We conclude that n-3 polyunsaturated fatty acids can be administered to prevent inflammation in ulcerative colitis, but they cause a decrease in the colonic antioxidant defense system, promoting oxidative injury at the site of inflammation.

Animals↗

PubMed1993

Vitamin E alters hepatic antioxidant enzymes in rats treated with dehydroepiandrosterone (DHEA).

The effects of vitamin E on hepatic antioxidant enzymes and plasma indicators of tissue damage were studied in rats treated with dehydroepiandrosterone (DHEA). Thirty-two male Sprague-Dawley rats were randomly allotted to one of four groups of eight rats each. Rats were treated with DHEA [100 mg/(kg body wt.d), i.p.], vitamin E (1 g/kg diet), or DHEA+vitamin E, or were untreated (controls) for 5 wk. Treatment with DHEA reduced (P < 0.05) weight gain, fat pad weight and carcass lipid concentration and increased carcass protein and ash concentration compared with control rats. The DHEA-treated rats had significantly lower concentrations of serum triglycerides and total cholesterol, yet greater amounts of liver lipid, than did control rats. Supplementation of DHEA-treated rats with vitamin E had no significant effect on weight gain, carcass composition or plasma metabolites compared with rats treated with DHEA alone. The rate of hepatic peroxisomal fatty acid oxidation in DHEA-treated rats was approximately 240% of that in control or vitamin E-supplemented rats. The specific activities of enzymes that defend against oxidative stress (e.g., glutathione reductase, glutathione transferase, catalase) or are indicators of tissue damage (e.g., alanine and aspartate aminotransferases) were all significantly higher in DHEA-treated rats compared with control rats. Supplementation of DHEA-treated rats with vitamin E generally reduced these indices of oxidative stress compared with rats treated with DHEA alone, suggesting that vitamin E may have a protective effect against potential oxidative damage associated with DHEA treatment.

Animals↗

PubMed1993

Myocardial antioxidant defenses during cardiopulmonary bypass.

In 31 male patients undergoing coronary bypass surgery who underwent different periods of cardioplegic hypothermic arrest, the activities of glutathione peroxidase, glutathione reductase, glutathione transferase, copper/zinc-containing and manganese-containing superoxide dismutases, and catalase were studied in the right atrial myocardium, before and 5 minutes after aortic cross-clamping. The levels of thiobarbituric acid reactive substances (TBARS) and nonproteic thiol compounds (NP-SH) were also assessed. Prolonged ischemia followed by reperfusion induced activation of the major myocardial antioxidant enzymes with marked NP-SH depression and TBARS increase, despite cold crystalloid cardioplegic protection. These changes were significantly related to the duration of the ischemic arrest, suggesting: (1) that reperfusion free radical generation is dependent on the severity of the previous ischemic period; and (2) the occurrence of myocardial oxidative stress during cardiopulmonary bypass.

Adult↗

PubMed2005

Increased levels of catalase and cathepsin V/L2 but decreased TIMP-1 in keratoconus corneas: evidence that oxidative stress plays a role in this disorder.

PURPOSE: The mRNA levels of antioxidant enzymes, matrix metalloproteinases, cathepsin V/L2, and tissue inhibitor of matrix metalloproteinases (TIMPs) were determined in keratoconus and normal corneas. Protein levels or enzyme activities were analyzed when RNA levels were different. METHODS: A total of 25 physiologic (normal) and 32 keratoconus corneas were studied. mRNAs were analyzed by semiquantitative reverse transcription-polymerase chain reaction and Southern blot analysis. Proteins were assessed by immunohistochemistry and/or Western blot analysis. Catalase activity was measured in corneal extracts. Antioxidant enzymes examined were catalase, superoxide dismutase (SOD)-1, SOD3, glutathione reductase, glutathione S-transferase and aldehyde dehydrogenase 3A1. Degradative enzymes examined were cathepsin V/L2 and matrix metalloproteinase (MMP)-1, -2, -7, -9, and -14. Tissue inhibitor of matrix metalloproteinase (TIMP)-1, -2, and -3 were also examined. RESULTS: Keratoconus corneas exhibited a 2.2-fold increase of catalase mRNA level (P < 0.01) and 1.8-fold of enzyme activity (P < 0.03); a 1.5-fold increase of cathepsin V/L2 mRNA (P < 0.03) and abnormal protein distribution; and a 1.8-fold decrease of TIMP-1 mRNA (P < 0.05) and 2.8-fold decrease of protein (P < 0.0001) compared with normal (physiologic) corneas. RNA levels for other antioxidant and degradative enzymes were similar between normal and keratoconus corneas. CONCLUSIONS: Keratoconus corneas have elevated levels of cathepsins V/L2, -B, and -G, which can stimulate hydrogen peroxide production, which, in turn, can upregulate catalase, an antioxidant enzyme. In addition, decreased TIMP-1 and increased cathepsin V/L2 levels may play a role in the matrix degradation that is a hallmark of keratoconus corneas. The findings support the hypothesis that keratoconus corneas undergo oxidative stress and tissue degradation.

Aldehyde Dehydrogenase↗

PubMed2001

Total antioxidant capacity and nuclear DNA damage in keratinocytes after exposure to H2O2.

Studies of oxidative stress have classically been performed by analyzing specific, single antioxidants. In this study, susceptibility to oxidative stress in the human keratinocyte cell line NCTC2544 exposed to hydrogen peroxide (H2O2) was measured by the TOSC (total oxyradical scavenging capacity) assay, which discriminates between the antioxidant capacity toward peroxyl radicals and hydroxyl radical. The generation of H2O2-induced DNA damage, total antioxidant capacity and levels of antioxidant enzymes (catalase, superoxide dismutase, glutathione reductase, glutathione S-transferase, glutathione peroxidase) were studied. Exposure to H2O2-induced DNA damage that was gradually restored while a significant reduction in cellular TOSC values was obtained independently of stressor concentrations and the degree of DNA repair. Whereas TOSC values and cell resistance to H2O2 showed a good relationship, the extent of DNA damage is independent from cellular total antioxidant capacity. Indeed, maximum DNA damage and cell mortality were observed in the first 4 h, whereas TOSC remained persistently low until 48 h. Catalase levels were significantly lower in exposed cells after 24 and 48 h. Keratinocytes exposed after 48 h to a second H2O2 treatment exhibited massive cell death. A possible linkage was observed between TOSC values and NCTC2544 resistance to H2O2 challenge. The TOSC assay appears to be a useful tool for evaluating cellular resistance to oxidative stress.

Antioxidants↗

PubMed1992

Curative effect of methionine on certain enzymes of chick kidney cortex under lanthanum toxicity situation.

Acute single dose administration of lanthanum chloride (250 mg/kg body wt, ip) to chicks have been found to alter the levels of enzymes of the antioxidant defence system of chick renal cortex fractions. Such changes involved significant decrease in activities of glucose-6-phosphate dehydrogenase, glutathione reductase, glutathione peroxidase and catalase of kidney epithelial cells. However glutathione-S-transferase activity was not altered. Glutathione and total thiol contents were decreased while lipoperoxidative reactions in kidney-cortex was significantly enhanced. The data indicate that amelioration of lanthanum toxicity condition by methionine supplementation may be due to the methionine serving as a precursor of glutathione.

Animals↗

PubMed1983

Comparative effects of dietary administration of antioxidants and inducers on the activities of several hepatic enzymes in mice.

Feeding mice with anticarcinogenic antioxidants, 2 (3)-tert-butyl-4-hydroxyanisole (BHA), ethoxyquin (EQ), disulfiram (DSF), and selenite (SE) resulted in selective changes in hepatic microsomal mixed function oxidases and in other enzymatic activities which were different from those obtained by feeding phenobarbital (PB), 3-methyl cholanthrene (MC), and Aroclor (ARO). While the hepatic microsomal oxidation of benzo(a)pyrene was markedly elevated by MC and ARO, it was decreased by BHA, EQ, and SE, and unchanged by PB and DSF. In addition, differential effects on cytochrome P-450, aminopyrine demethylase, and aniline hydroxylase were observed. In marked contrast to the large increases produced by BHA, EQ, and ARO, the feeding of PB, MC, or SE resulted in little or no increase in epoxide hydrolase, UDP-glucuronyl transferase, UDP-glucose dehydrogenase, glutathione reductase, glutathione S-transferase, and glutathione levels. These results suggest that protective effects of anticarcinogens may be produced by both the decrease of metabolic activation (BHA, EQ, SE) and the enhancement of metabolic deactivation processes (BHA, EQ, DSF, SE).

Animals↗

PubMed1975

The partial purification and properties of a human erythrocyte 4-nitroacetophenone reductase.

1. A soluble enzyme which catalyses the NADPH-dependent reduction of 4-nitroacetophenone to 4-nitrophenylmethylcarbinol has been partially purified from human erythrocytes. 2.inter-individual or intra-individual differences in the enzymic activity were small except for very low activity observed in one subject with glucose 6-phosphate dehydrogenase deficiency resulting in decreased levels of NADPH. 3. The enzyme was inactivated above 50 degrees or on storage at 4 degrees for longer than 24 h. The pH optimum was between 7-0-8-0. 4. the enzyme has been differentiated from NADPH-methaemoglobin reductase, NADPH-cytochrome c reductase, glutathione reductase, alpha,beta-unsaturated ketone reductase and aromatic alpha-keto acid reductase activities, but similarities exist between this enzyme and a rabbit kidney cortex aromatic aldehyde/ketone reductase.

Acetophenones↗

PubMed1991

Antiperoxidative enzymes in Retama and their seasonal variation.

The antiperoxidative enzymatic activities of ascorbate peroxidase, dehydroascorbate reductase, glutathione reductase and catalase and the content of the antioxidants ascorbate and glutathione were followed in the legume Retama (Retama reatem) in the desert. Antiperoxidative enzymatic activities and antioxidants content were related to seasonal variations in irradiance and precipitation. Retama was found to possess a very efficient removal mechanism for hydrogen peroxide as was shown by the high catalase activity and the high affinity of the ascorbate-glutathione pathway enzymes to their substrates. The increase in irradiance during the spring (March to May) was accompanied by increasing antioxidative enzymatic activities and ascorbate content. A marked enhancement in catalase activity also accompanied the increased light intensity during the spring. Changes in the enzymatic activities of the ascorbate-glutathione pathway followed the increased ascorbate content. These results suggest that physiological adaptation of Retama involves efficient H2O2 removal mechanisms which respond to different seasonal and environmental stresses.

Ascorbate Peroxidases↗

PubMed2001

Chemomodulation of carcinogen metabolising enzymes, antioxidant profiles and skin and forestomach papillomagenesis by Spirulina platensis.

Numerous reports have revealed an inverse association between consumption of some selective natural products and risk of developing cancer. In the present study the effect of 250 and 500 mg/kg body wt. of Spirulina was examined on drug metabolising phase I and phase II enzymes, antioxidant enzymes, glutathione content, lactate dehydrogenase and lipid peroxidation in the liver of 7-week-old Swiss albino mice. The implications of these biochemical alterations have been further evaluated adopting the protocol of benzo(a)pyrene induced forestomach and 7,12 dimethylbenz(a)anthracene (DMBA) initiated and croton oil promoted skin papillomagenesis. Our primary findings reveal the 'Monofunctional' nature of Spirulina as deduced from its potential to induce only the phase II enzyme activities associated mainly with carcinogen detoxification. The glutathione S-transferase and DT-diaphorase specific activities were induced in hepatic and all the extrahepatic organs examined (lung, kidney and forestomach) by Spirulina pretreatment (significance level being from p < 0.05 to p < 0.005) except for the low dose treatment in forestomach. With reference to antioxidant enzymes viz., superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase and reduced glutathione were increased significantly by both the chosen doses of Spirulina from p < 0.01 to p < 0.005. Chemopreventive response was quantitated by the average number of papillomas per effective mouse (tumor burden) as well as percentage of tumor bearing animals. There was a significant inhibition of tumor burden as well as tumor incidence in both the tumor model systems studied. In the skin tumor studies tumor burden was reduced from 4.86 to 1.20 and 1.15 by the low and high dose treatment respectively. In stomach tumor studies tumor burden was 2.05 and 1.73 by the low and high doses of Spirulina treatment against 3.73 that of control.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1986

Charge redistribution in proteins via linear hydrogen-bond chains.

It is proposed that proteins might activate specific atomic positions within bound substrates or co-factors by means of hydrogen-bond chains. As a result of a concerted proton (tautomeric) shift in the linked residues of the hydrogen-bond chain, which includes the bound molecule, a charge separation occurs. The charge thus generated at a specific atom of the bound molecule renders it nucleophilic or electrophilic, as the case may be, and hence 'activated' towards subsequent chemical events. To test the feasibility of the theory a survey of published X-ray diffraction determined structures was performed. A search was made for hydrogen-bond chains which emanate away from bound substrates, co-factors or metal ions in order to validate the existence of such structural arrangements. Secondly, an attempt was made to incorporate the proposed proton dynamics into the proteins' mechanisms of action. Examples in which these criteria were satisfied are carboxypeptidase A, carbonic anhydrase, haemoglobin, dihydrofolate reductase, glutathione reductase and p-hydroxybenzoate hydroxylase.

Binding Sites↗

PubMed2004

Pre-extraction preparation (fresh, frozen, freeze-dried, or acetone powdered) and long-term storage of fruit and vegetable tissues: effects on antioxidant enzyme activity.

Activities of the antioxidant enzymes ascorbate peroxidase, catalase, dehydroascorbate reductase, glutathione reductase, guaiacol peroxidase, monodehydroascorbate reductase, and superoxide dismutase were assayed in honeydew (Cucumis melo L.) fruit and spinach (Spinacia oleracea L.) leaves either as fresh, frozen to -80 degrees C, frozen in liquid nitrogen, freeze-dried, or acetone powder, representing the various ways tissues are treated prior to enzyme extraction. Treated tissues were analyzed following treatment or stored for up to 8 weeks at -80 degrees C. Enzyme activities in fruit frozen with or without liquid nitrogen and leaves frozen with or without liquid nitrogen or freeze-dried were equal to those of fresh tissue. Enzyme activities in freeze-dried or acetone-powdered fruit and leaves and in acetone-powdered tissues were significantly higher or lower than those in fresh tissue. Enzyme activities in both tissues frozen with or without liquid nitrogen and stored for 8 weeks at -80 degrees C changed little; those in freeze-dried and acetone-powdered tissues, however, significantly increased/decreased over the same period. Fresh tissue should be used in antioxidant enzyme assays, but if storage is necessary, tissues should be placed directly into a -80 degrees C freezer.

Antioxidants↗