Early habituation of maize (Zea mays) suspension-cultured cells to 2,6-dichlorobenzonitrile is associated with the enhancement of antioxidant status.

The cellulose biosynthesis inhibitor 2,6-dichlorobenzonitrile (DCB) has been widely used to gain insights into cell wall composition and architecture. Studies of changes during early habituation to DCB can provide information on mechanisms that allow tolerance/habituation to DCB. In this context, maize-cultured cells with a reduced amount of cellulose (∼20%) were obtained by stepwise habituation to low DCB concentrations. The results reported here attempt to elucidate the putative role of an antioxidant strategy during incipient habituation. The short-term exposure to DCB of non-habituated maize-cultured cells induced a substantial increase in oxidative damage. Concomitantly, short-term treated cells presented an increase in class III peroxidase and glutathione S-transferase activities and total glutathione content. Maize cells habituated to 0.3-1 µM DCB (incipient habituation) were characterized by a reduction in the relative cell growth rate, an enhancement of ascorbate peroxidase and class III peroxidase activities, and a net increment in total glutathione content. Moreover, these cell lines showed increased levels of glutathione S-transferase activity. Changes in antioxidant/conjugation status enabled 0.3 and 0.5 µM DCB-habituated cells to control lipid peroxidation levels, but this was not the case of maize cells habituated to 1 µM DCB, which despite showing an increased antioxidant capacity were not capable of reducing the oxidative damage to control levels. The results reported here confirm that exposure and incipient habituation of maize cells to DCB are associated with an enhancement in antioxidant/conjugation activities which could play a role in incipient DCB habituation of maize-cultured cells.

Quantitative proteomics identifies the membrane-associated peroxidase GPx8 as a cellular substrate of the hepatitis C virus NS3-4A protease.

UNLABELLED: The hepatitis C virus (HCV) NS3-4A protease is not only an essential component of the viral replication complex and a prime target for antiviral intervention but also a key player in the persistence and pathogenesis of HCV. It cleaves and thereby inactivates two crucial adaptor proteins in viral RNA sensing and innate immunity, mitochondrial antiviral signaling protein (MAVS) and TRIF, a phosphatase involved in growth factor signaling, T-cell protein tyrosine phosphatase (TC-PTP), and the E3 ubiquitin ligase component UV-damaged DNA-binding protein 1 (DDB1). Here we explored quantitative proteomics to identify novel cellular substrates of the NS3-4A protease. Cell lines inducibly expressing the NS3-4A protease were analyzed by stable isotopic labeling using amino acids in cell culture (SILAC) coupled with protein separation and mass spectrometry. This approach identified the membrane-associated peroxidase GPx8 as a bona fide cellular substrate of the HCV NS3-4A protease. Cleavage by NS3-4A occurs at Cys 11, removing the cytosolic tip of GPx8, and was observed in different experimental systems as well as in liver biopsies from patients with chronic HCV. Overexpression and RNA silencing studies revealed that GPx8 is involved in viral particle production but not in HCV entry or RNA replication. CONCLUSION: We provide proof-of-concept for the use of quantitative proteomics to identify cellular substrates of a viral protease and describe GPx8 as a novel proviral host factor targeted by the HCV NS3-4A protease.

In vitro antioxidant properties, free radicals scavenging activities of extracts and polyphenol composition of a non-timber forest product used as spice: Monodora myristica.

BACKGROUND: Excessive production of free radicals causes direct damage to biological molecules such as DNA, proteins, lipids, carbohydrates leading to tumor development and progression. Natural antioxidant molecules from phytochemicals of plant origin may directly inhibit either their production or limit their propagation or destroy them to protect the system. In the present study, Monodora myristica a non-timber forest product consumed in Cameroon as spice was screened for its free radical scavenging properties, antioxidant and enzymes protective activities. Its phenolic compound profile was also realized by HPLC. RESULTS: This study demonstrated that M. myristica has scavenging properties against DPPH(•), OH(•), NO(•), and ABTS(•) radicals which vary in a dose depending manner. It also showed an antioxidant potential that was comparable with that of Butylated Hydroxytoluene (BHT) and vitamin C used as standard. The aqueous ethanol extract of M. myristica barks (AEH); showed a significantly higher content in polyphenolic compounds (21.44 ± 0.24 mg caffeic acid/g dried extract) and flavonoid (5.69 ± 0.07 quercetin equivalent mg/g of dried weight) as compared to the other studied extracts. The HPLC analysis of the barks and leaves revealed the presence of several polyphenols. The acids (3,4-OH-benzoic, caffeic, gallic, O- and P- coumaric, syringic, vanillic), alcohols (tyrosol and OH-tyrosol), theobromine, quercetin, rutin, catechine and apigenin were the identified and quantified polyphenols. All the tested extracts demonstrated a high protective potential on the superoxide dismutase (SOD), catalase and peroxidase activities. CONCLUSION: Finally, the different extracts from M. myristica and specifically the aqueous ethanol extract reveal several properties such as higher free radical scavenging properties, significant antioxidant capacities and protective potential effects on liver enzymes.

Benzothiadiazole effect in the compatible tomato-Meloidogyne incognita interaction: changes in giant cell development and priming of two root anionic peroxidases.

MAIN CONCLUSION: BTH application is effective in root-knot nematode-tomato interaction in a way that involves a delay in the formation of nematode feeding site and triggers molecular responses at several levels. The compatible interaction between root-knot nematodes and their hosts requires the nematode to overcome plant defense systems so that a sophisticated permanent feeding site (giant cells) can be produced within the host roots. It has been suggested that activators of plant defenses may provide a novel management strategy for controlling root-knot nematodes but little is known about the molecular basis by which these elicitors operate. The role of pre-treatment with Benzothiadiazole (BTH), a salicylic acid analog, in inducing resistance against Meloidogyne incognita infection was investigated in tomato roots. A decrease in galling in roots and feeding site numbers was observed following BTH treatment. Histological investigations showed a delay in formation of feeding sites in treated plants. BTH-treated galls had higher H2O2 production, lignin accumulation, and increased peroxidase activity than untreated galls. The expression of two tomato genes, Tap1 and Tap2, coding for anionic peroxidases, was examined by qRT-PCR and in situ hybridization in response to BTH. Tap1 was induced at all infection points, reaching the highest level at 15 dpi. Tap2 expression, although slightly delayed in untreated galls, increased during infection in both treated and untreated galls. The expression of Tap1 and Tap2 was observed in giant cells of untreated roots, whereas the transcripts were localized in both giant cells and in parenchyma cells surrounding the developing feeding sites in treated plants. These results show that BTH applied to tomato plants makes them more resistant to infection by nematodes, which become less effective in overcoming root defense pathway.

Effect of soil salinity on physiological characteristics of functional leaves of cotton plants.

This study analyzes the effects of soil salinity on fatty acid composition, antioxidative enzyme activity, lipid peroxidation, and photosynthesis in functional leaves during the flowering and boll-forming stages of two cotton cultivars, namely, CCRI-44 (salt-tolerant) and Sumian 12 (salt-sensitive), grown under different soil salinity conditions. Saturated (C16:0 and C18:0) and unsaturated fatty acid (FA) contents (C18:1), as well as superoxide dismutase activity increased, whereas high-unsaturated FA (C18:2 and C18:3) decreased, with the increase in soil salinity. The production of malondialdehyde increased with increasing lipoxygenase (LOX) activity, indicating that LOX catalyzed FA peroxidation under salt stress. Soil salinity had no significant effect on catalase (CAT) and peroxidases (POD) activity in the salt-sensitive cultivar Sumian 12, but significantly increased CAT and POD activities in the salt-tolerant cultivar CCRI-44. Net photosynthesis and stomatal conductance of the cotton cultivars decreased in response to salt stress; however, CCRI-44 showed a smaller reduction in photosynthesis than Sumian 12. The results indicated that stomatal apparatus limited leaf photosynthetic capacity in the salinity-treated plants of both cultivars. The net photosynthetic rate, maximum photochemical efficiency, and photochemical quantum yield of the cotton functional leaves showed positive correlation with double-bond index (DBI). These results suggested that salt stress caused DBI reduction and decreased the photochemical conversion efficiency of solar radiation and, thereby resulting in lower net photosynthetic rates.

[Function of nitric oxide in initiating production of lignin degrading peroxidases by Phanerochaete chrysosporium].

OBJECTIVE: By analyzing the function and mechanism of nitric oxide in initiating producing lignin peroxidases by phanerochaete chrysosporium, we studied the regulation mechanism triggering the secondary metabolism of white-rot fungi. METHODS: Mutant (pcR5305) and wild-type (pc530) strains of phanerochaete chrysosporium were respectively cultured under both the conditions of nitrogen limitation and nitrogen sufficiency. To compare their lignin peroxidases (LiP)-production and nitric oxide(NO)-production kinetics and their different influences on producing LiP after the NO donor Sodium Nitroprusside (SNP) and scavenger cPTIO were respectively added to the nitrogen limitation or sufficiency culture medium to show the function and mechanism of nitric oxide in initiating production of lignin peroxidases by white-rot fungi. RESULTS: Both strains produced nitric oxide (NO) under the two opposite nutritional conditions, but the levels of NO produced were related with the type of strain and the nutritional conditions. Strain pc530 produced NO requiring nutrition depletion and producing of NO was strongly delayed and reduced when it was cultured under nitrogen sufficiency condition. On the contrary, pcR5305 did not require nitrogen depletion to trigger and the levels of NO were higher than that of pc530. The results indicate that LiP content had positive correlation with NO value except the occurrence time of LiP peak value was later than that of NO. The ability of producing LiP was promoted after the NO donor SNP added, but SNP affected more on pc530 than pcR5305 in promoting producing LiP. 15mM cPTIO would greatly repress producing LiP, but could not completely restrain the synthesis of LiP for both strains. CONCLUSION: By producing NO, Phanerochaete chrysosporium triggers LiP synthesis. However, the evidences do not indicate that NO participates or effect directly in LiP synthesis. It is more likely that NO is reacting as an upstream signal molecule. Besides NO, there are other signal molecules that have a positive effect on NO levels also involving in the regulation producing LiP. The mechanism of the resistance to nutritional repression of pcR5305 in synthesizing lignin degrading peroxidases may be the answer to the different NO production mechanism of pcR5305 from pc530.

[Silibinin and its hepatoprotective action from the perspective of a toxicologist]. / Sylibinina i jej dzialanie hepatoprotekcyjne z punktu widzenia toksykologa.

Silibinin is the most active component of a complex of flavonoids -silymarin contained in fruit milk thistle (Sylibum marianum). Its mechanism of action is complex and highly beneficial in protecting hepatocytes. On the one hand this compound blocks the penetration of various toxins (for example amanitin) into the hepatocytes not allowing in this way for the cell death and on the other hand, it prevents apoptosis through intracellular. It protects the liver from oxidative intracellular free radicals by increasing the activity of enzyme superoxide dismutase and peroxidase, as well as by increasing the concentration of glutathione and the activity of the peroxidase. Silibinin strengthens and stabilizes the cell membranes, inhibits the synthesis of prostaglandins associated with the lipid peroxidation and promotes regeneration of liver through the stimulation of protein synthesis and effect on the production of new hepatocytes. A particularly interesting topic from the perspective of a toxicologist is the application of silibinin in Amanita phalloides poisoning. Clinical trials conducted in this respect are very encouraging. The other beneficial application of silibinin is in therapy of the alcoholic liver cirrhosis. The evidence shows that the use of silymarin leads to a significant reduction in liver-related mortality and even reduction in the number of patients with encephalopathy in the course of the disease. Application of silibinin goes beyond liver disease and expands in the direction of cancer and even diabetes. What is interesting is the fact, that the substance of herbal origin occurring in the environment is so strong, favorable, beneficial and multidirectional. Science has contributed to improving the bioavailability of silibinin thus making it more effective.

Bromide-dependent toxicity of eosinophil peroxidase for endothelium and isolated working rat hearts: a model for eosinophilic endocarditis.

Eosinophilic endocarditis is a potentially lethal complication of chronic peripheral blood hypereosinophilia. We hypothesized that eosinophil peroxidase (EPO), an abundant eosinophil (EO) cationic granule protein, promotes eosinophilic endocarditis by binding to negatively charged endocardium, and there generating cytotoxic oxidants. Using an immunocytochemical technique, we demonstrated endocardial deposition of EPO in the heart of a patient with hypereosinophilic heart disease. Because EPO preferentially oxidizes Br- to hypobromous acid (HOBr) rather than Cl- to hypochlorous acid (HOCl) at physiologic halide concentrations, we characterized the Br(-)-dependent toxicity of both activated EOs and purified human EPO towards several types of endothelial cells and isolated working rat hearts. In RPMI supplemented with 100 microM Br-, phorbol myristate acetate-activated EOs, but not polymorphonuclear leukocytes, caused 1.8-3.6 times as much 51Cr release from four types of endothelial cell monolayers as in RPMI alone. H2O2 and purified human EPO, especially when bound to cell surfaces, mediated extraordinarily potent, completely Br(-)-dependent cytolysis of endothelial cells that was reversed by peroxidase inhibitors, HOBr scavengers, and competitive substrates. We further modeled eosinophilic endocarditis by instilling EPO into the left ventricles of isolated rat hearts, flushing unbound EPO, then perfusing them with a buffer containing 100 microM Br- and 1 microM H2O2. Acute congestive heart failure (evidenced by a precipitous decrement in rate pressure product, stroke volume work, aortic output, and MVO2 to 0-33% of control values) ensued over 20 min, which deletion of EPO, Br-, or H2O2 completely abrogated. These findings raise the possibility that EPO bound to endocardial cells might utilize H2O2 generated either by overlying phagocytes or endogenous cardiac metabolism along with the virtually inexhaustible supply of Br- from flowing blood to fuel HOBr-mediated cell damage. By this mechanism, EPO may play an important role in the pathogenesis of eosinophilic endocarditis.

Ecotoxicological effects of aluminum and zinc on growth and antioxidants in Lemna minor L.

The present study aimed at investigating effects of zinc and aluminum (0.15 and 0.3mM) in duckweed (Lemna minor L.) over a 15-day period. High bioaccumulation of both metals was accompanied by an increase in dry weight under higher metal treatments. Antioxidant response was observed under both metal stresses, with large increases in superoxide dismutase and peroxidases. Catalase activity declined only in duckweed exposed to Zn while lipid peroxidation as well as H(2)O(2), proline and ascorbate levels increased. The results suggest induction of oxidative stress under both aluminum and zinc toxicity, and also demonstrate duckweed's capacity to upregulate its antioxidative defense. Additionally, Zn was found to be more toxic than Al to duckweed for the concentrations applied. Due to its high bioaccumulation potential and tolerance via increased antioxidant capacity, duckweed has a potential for phytoremediation of water bodies polluted by low levels of zinc and aluminum.

Pectin Demethylesterification Generates Platforms that Anchor Peroxidases to Remodel Plant Cell Wall Domains.

Plant cell walls are made of polysaccharidic-proteinaceous complex matrices. Molecular interactions governing their organization remain understudied. We take advantage of the highly dynamic cell walls of Arabidopsis seed mucilage secretory cells to propose a hierarchical multi-molecular interaction model within a cell wall domain. We show that the PECTINMETHYLESTERASE INHIBITOR6 activity creates a partially demethylesterified pectin pattern acting as a platform allowing positioning of PEROXIDASE36 in a remote primary cell wall domain during early development. This allows triggering the loosening of this domain during later development, in turn leading to proper physiological function upon mature seed imbibition and germination. We anticipate that this pioneer example of molecular scaffold within a cell wall domain is more widespread through other combinations of the individual molecular players all belonging to large multigenic families. These results highlight the role of cell wall polysaccharide-protein interactions in the organization of cell wall domains.

Multifaceted activities of plant gum synthesised platinum nanoparticles: catalytic, peroxidase, PCR enhancing and antioxidant activities.

A single pot, green method for platinum nanoparticles (Pt NP) production was devised with gum ghatti (Anogeissus latifolia). Analytical tools: ultraviolet-visible (UV-vis), dynamic light scattering, zeta potential, transmission electron microscope, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy were employed. Wide continuous UV-vis absorption and black solution colouration proved Pt NP formation. Face-centred cubic crystalline structure of NP was evidenced from XRD. NPs formed were nearly spherical with a mean particle size of 3 nm. NP demonstrated a myriad of properties including catalytic, peroxidase, polymerase chain reaction (PCR) enhancing and antioxidant activities. Catalytic action of NP was probed via NaBH4 reduction of arsenazo-III dye. NP displayed considerable peroxidase activity via catalysis of 3, 3', 5, 5'-tetramethylbenzidine oxidation by H2O2. NP showed exceptional stability towards varying pH (3-11), temperature (25-100°C), salt concentration (0-100 mM) and storage time duration (0-12 months). In comparison with horse radish peroxidase, its applicability as an artificial peroxidase is advantageous. NP caused a two-fold enhancement in PCR yield at 0.4 nM. Also showed significant 1', 1' diphenyl picryl-hydrazyle scavenging (80.1%) at 15 µg/mL. Author envisages that the biogenic Pt NP can be used in a range of biological and environmental applications.

Effects of Cistus-tea on bacterial colonization and enzyme activities of the in situ pellicle.

OBJECTIVES: Polyphenols are expected to have antibacterial properties. Cistus is a tea rich in polyphenols. The aim of the present in situ study was to investigate the effect of Cistus-tea on the pellicle and on the initial oral biofilm. METHODS: For in situ pellicle formation and initial biofilm formation, bovine enamel slabs were fixed on maxillary splints and carried by four subjects at buccal sites for up to 2 h. Bacteria present in 120-min pellicles were determined with DAPI-staining and fluorescence in situ hybridization with and without a 10 min rinse with Cistus-tea performed 1 min after incorporation of the slabs. In addition, amylase, lysozyme, glucosyltransferase and peroxidase activities immobilised in the pellicle layer were measured before and after rinsing for 10 min with Cistus-tea. RESULTS: The amount of bacteria detected in the 120-min biofilm was reduced significantly, if a 10 min rinse with Cistus-tea was performed one min after insertion of the enamel slabs. DAPI-staining yielded 13.2+/-3.5 for controls and 6.5+/-1.1 x 10(4) bacteria/cm(2), if a rinse with Cistus-tea was applied. Lysozyme, amylase and glucosyltransferase activities immobilised in the pellicle were not affected following a rinse with Cistus-tea. However, peroxidase activity was reduced significantly. CONCLUSIONS: Cistus-tea may be used to reduce the initial bacterial adhesion in the oral cavity.

Effect of copper excess on H2O2 accumulation and peroxidase activities in bean roots.

We studied oxidative stress and peroxidase activity resulting from application of excess copper in the nutrient medium on the roots of young bean seedlings. The change in H2O2 content, lipid peroxidation and antioxidant enzymes activities were quantified and located. Excess of copper caused a loss of membrane integrity and the formation of hydrogen peroxide (H2O2) as visualized in the transmission electron microscopy and measured using spectrophotometry. H2O2 accumulated in the intercellular spaces and in the cell wall. The production of H2O2 was accompanied by an increase in the activity of soluble and ionic GPX (guaiacol peroxidase, EC 1.11.17), CAPX (coniferyl alcohol peroxidase) and NADH oxidase.

Effects of molecular weight of hyaluronic acid on its viscosity and enzymatic activities of lysozyme and peroxidase.

OBJECTIVES: To investigate the effects of the molecular weight of hyaluronic acid on its viscosity and enzymatic activities of lysozyme and peroxidase in solution and on the hydroxyapatite surface. DESIGN: Hyaluronic acids of four different molecular weights (10 kDa, 100 kDa, 1 MDa, and 2 MDa), hen egg-white lysozyme, bovine lactoperoxidase, and human whole saliva were used. Viscosity values of hyaluronic acids were measured using a cone-and-plate viscometer at six different concentrations (0.1-5.0 mg/mL). Enzymatic activities of lysozyme and peroxidase were examined by hydrolysis of fluorescein-labeled Micrococcus lysodeikticus and oxidation of fluorogenic 2',7'-dichlorofluorescein to fluorescing 2',7'-dichlorofluorescein, respectively. RESULTS: In solution assays, only 2 MDa-hyaluronic acid significantly inhibited lysozyme activities in saliva. In surface assays, hyaluronic acids inhibited lysozyme and peroxidase activities; the inhibitory activities were more apparent with high-molecular-weight ones in saliva than in purified enzymes. The 100 kDa-hyaluronic acid at 5.0 mg/mL, 1 MDa-one at 0.5 mg/mL, and 2 MDa-one at 0.2 mg/mL showed viscosity values similar to those of human whole saliva at a shear rate range required for normal oral functions. The differences among the influences of the three conditions on the enzymatic activities were not statistically significant. CONCLUSIONS: High-molecular-weight hyaluronic acids at low concentration and low-molecular-weight ones at high concentration showed viscosity values similar to those of human whole saliva. Inhibitory effects of hyaluronic acids on lysozyme and peroxidase activities were more significant with high-molecular-weight ones on the surface and in saliva compared with in solution and on purified enzymes.

VPO1 Modulates Vascular Smooth Muscle Cell Phenotypic Switch by Activating Extracellular Signal-regulated Kinase 1/2 (ERK 1/2) in Abdominal Aortic Aneurysms.

Background Hydrogen peroxide (H2O2) is a critical molecular signal in the development of abdominal aortic aneurysm ( AAA ) formation. Vascular peroxidase 1 ( VPO 1) catalyzes the production of hypochlorous acid ( HOC l) from H2O2 and significantly enhances oxidative stress. The switch from a contractile phenotype to a synthetic one in vascular smooth muscle cells ( VSMC s) is driven by reactive oxygen species and is recognized as an early and important event in AAA formation. This study aims to determine if VPO 1 plays a critical role in the development of AAA by regulating VSMC phenotypic switch. Methods and Results VPO 1 is upregulated in human and elastase-induced mouse aneurysmal tissues compared with healthy control tissues. Additionally, KLF 4, a nuclear transcriptional factor, is upregulated in aneurysmatic tissues along with a concomitant downregulation of differentiated smooth muscle cell markers and an increase of synthetic phenotypic markers, indicating VSMC phenotypic switch in these diseased tissues. In cultured VSMC s from rat abdominal aorta, H2O2 treatment significantly increases VPO 1 expression and HOC l levels as well as VSMC phenotypic switch. In support of these findings, depletion of VPO 1 significantly attenuates the effects of H2O2 and HOC l treatment. Furthermore, HOC l treatment promotes VSMC phenotypic switch and ERK 1/2 phosphorylation. Pretreatment with U0126 (a specific inhibitor of ERK 1/2) significantly attenuates HOC l-induced VSMC phenotypic switch. Conclusions Our results demonstrate that VPO 1 modulates VSMC phenotypic switch through the H2O2/ VPO 1/ HOC l/ ERK 1/2 signaling pathway and plays a key role in the development of AAA . Our findings also implicate VPO 1 as a novel signaling node that mediates VSMC phenotypic switch and plays a key role in the development of AAA . Clinical Trial Registration URL : www.chictr.org.cn . Unique identifier: Chi CTR 1800016922.

Protective effects of salidroside on hydrogen peroxide-induced apoptosis in SH-SY5Y human neuroblastoma cells.

Oxidative stress plays an important role in Alzheimer's disease and other neurodegenerative disorders. Salidroside, a phenylpropanoid glycoside isolated from Rhodiola rosea L, shows potent antioxidant property. In this paper, the neuroprotective effects of salidroside on hydrogen peroxide (H2O2)-induced apoptosis in SH-SY5Y cells were investigated. Pretreatment with salidroside markedly attenuated H2O2-induced cell viability loss and apoptotic cell death in a dose-dependent manner. The mechanisms by which salidroside protected neuron cells from oxidative stress included the induction of several antioxidant enzymes, thioredoxin, heme oxygenase-1, and peroxiredoxin-I; the downregulation of pro-apoptotic gene Bax and the upregulation of anti-apoptotic genes Bcl-2 and Bcl-X(L). Furthermore, salidroside dose-dependently restored H2O2-induced loss of mitochondrial membrane potential as well as the elevation of intracellular calcium level. These results suggest that salidroside has protective effects against oxidative stress-induced cell apoptosis, which might be a potential therapeutic agent for treating or preventing neurodegenerative diseases implicated with oxidative stress.

Calcium chloride effects on salinity-induced oxidative stress, proline metabolism and indole alkaloid accumulation in Catharanthus roseus.

Catharanthus roseus (L.) G. Don. plants were grown with NaCl and CaCl2 in order to study the effect of CaCl2 on NaCl-induced oxidative stress in terms of lipid peroxidation (TBARS content), H2O2 content, osmolyte concentration, proline (PRO)-metabolizing enzymes, antioxidant enzyme activities, and indole alkaloid accumulation. The plants were treated with solutions of 80 mM NaCl, 80 mM NaCl with 5 mM CaCl2 and 5 mM CaCl2 alone. Groundwater was used for irrigation of control plants. Plants were uprooted randomly on 90 days after sowing (DAS). NaCl-stressed plants showed increased TBARS, H2O2, glycine betaine (GB) and PRO contents, decreased proline oxidase (PROX) activity, and increased gamma-glutamyl kinase (gamma-GK) activity when compared to control. Addition of CaCl2 to NaCl-stressed plants lowered the PRO concentration by increasing the level of PROX and decreasing the gamma-GK activities. Calcium ions increased the GB contents. CaCl2 appears to confer greater osmoprotection by the additive role with NaCl in GB accumulation. The antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased under salinity and further enhanced due to CaCl2 treatment. The NaCl-with-CaCl2-treated C. roseus plants showed an increase in total indole alkaloid content in shoots and roots when compared to NaCl-treated and untreated plants.

Differential effects of hexaconazole and paclobutrazol on biomass, electrolyte leakage, lipid peroxidation and antioxidant potential of Daucus carota L.

The application of triazole fungicides is a common practice in the cultivation of carrot (Daucus carota L.) plants. It is there for seems important to test the changes that are occurring in this food crop under triazoles, the non-traditional plant growth regulators, treatments in order to identify the extent to which it tolerate the fungicide application and thereby make it an economical food crop. A field experiment was conducted to find out the effects of two triazole fungicides (hexaconazole (HEX) and paclobutrazol (PBZ) at 20mg l(-1) plant(-1)) on the biomass, yield, electrolyte leakage, lipid peroxidation and antioxidant potential of carrot. The treatments were given to plants on 15, 30 and 45 days after sowing (DAS). The plants were uprooted for analyses of growth and biochemical parameters on 60 DAS. It was found that both HEX and PBZ have significant effects on the growth and biochemical parameters of this plant. Among the triazoles used, PBZ performed best in terms of anthocyanin, protein, amino acid, proline, starch and sugar, contents whereas HEX enhanced carotenoids, fresh weight, dry weight and biomass. There was no significant variation in chlorophyll ('a' and 'b') contents between the two triazole treated plants, but HEX and PBZ proved best when compared to untreated control plants. HEX and PBZ increased alpha- and beta-amylases enzymes activities to a significant level. Out of these two triazoles, PBZ performed best in increasing the starch hydrolyzing enzymes activities. The non-enzymatic antioxidant, reduced glutathione (GSH) and antioxidant enzyme ascorbate peroxidase (APX) were increased under fungicide applications. The data suggests that, the application of triazole fungicides may be a useful tool to increase the tuber quality as well as quantity in carrot plants, apart from their fungicidal properties.

Antioxidant potentials and ajmalicine accumulation in Catharanthus roseus after treatment with giberellic acid.

Changes in antioxidant potentials and indole alkaloid, ajmalicine, production were studied in Catharanthus roseus (L.) G. Don. plants under treatment with gibberellic acid (GA(3)). The GA(3) treatments were given in two ways, foliar spray and soil drenching methods on 30, 45, 60 and 75 days after planting (DAP). The plants were uprooted randomly on 90 DAP and separated into root, stem and leaves and used for analyses. The antioxidant potential was studied in terms of non-enzymatc antioxidant molecules like ascorbic acid (AA), alpha-tocopherol (alpha-toc) and reduced glutathione (GSH) and activities of antioxidant enzyme, viz., superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT). The alkaloid ajmalicine was extracted and estimated from roots of both control and treated plants. It was found that, GA(3) has a profound effect upon the antioxidant potentials and it caused a significant enhancement in the production of ajmalicine when compared to untreated control as well as foliar-sprayed plants. There was no significant enhancement in GSH and ajmalicine content under GA(3) foliar spray in C. roseus. These preliminary results suggest that, the application of GA(3) may be a useful tool to increase the antioxidant potential and alkaloid production in medicinal plants like C. roseus.

Induction of drought stress tolerance by ketoconazole in Catharanthus roseus is mediated by enhanced antioxidant potentials and secondary metabolite accumulation.

A pot culture experiment was conducted to estimate the drought stress mitigating effect of ketoconazole (KCZ), a fungicide cum plant growth regulator, in Catharanthus roseus plants. The plants under pot culture were subjected to drought stress and drought stress with KCZ from 30 days after sowing (DAS) and regular irrigation was kept as control. Antioxidant contents and activities of antioxidant enzymes were estimated from root, stem and leaf of both control and treated plants. The alkaloid ajmalicine was extracted and estimated from the roots of control, drought stressed and KCZ treated plants. Individual and combined drought stress and KCZ treatments increased ascorbic acid, alpha-tocopherol contents, superoxide dismutase, ascorbate peroxidase, catalase and polyphenol oxidase activities when compared to control. There was a significant enhancement in ajmalicine production under KCZ treated plants under drought stress when compared to well watered control as well as drought stressed plants. The KCZ treatment resulted in partial mitigation of drought stress by increasing the antioxidant potentials in C. roseus plants.