sundar mety | Gulbarga - Academia.edu (original) (raw)

Papers by sundar mety

New Phytologist, Jan 1, 2003

Food chemistry, Jan 1, 2006

The antioxidant properties of 25 edible tropical plants, expressed as Trolox equivalent antioxida... more The antioxidant properties of 25 edible tropical plants, expressed as Trolox equivalent antioxidant capacity (TEAC), were studied using DPPH (1,1-diphenyl-2-picrylhydrazyl free radical) scavenging and reducing ferric ion antioxidant potential (FRAP) assays. Their cupric ion chelating activities (CCA) and total polyphenol contents (TPC) were also determined. A strong correlation between TEAC values obtained for the DPPH assay (TEAC DPPH ) and those for the FRAP assay (TEAC FRAP ) implied that compounds in the extracts were capable of scavenging the DPPH free radical and reducing ferric ions. A satisfactory correlation of TPC with TEAC DPPH and TEAC FRAP suggested that polyphenols in the extracts were partly responsible for the antioxidant activities while its correlation with CCA was poor, indicating that polyphenols might not be the main cupric ion chelators. Principal component analysis (PCA) indicated that TEAC DPPH , TEAC FRAP and TPC contributed to the total variation in the antioxidant activities of the plants.

Food Chemistry, Jan 1, 2005

In this study, the methanolic extracts and lichens acids obtained from six Umbilicaria species we... more In this study, the methanolic extracts and lichens acids obtained from six Umbilicaria species were tested for their antimicrobial activity (against three Grampositive bacteria, five Gram-negative bacteria and two yeasts species) and their antioxidant activity. Total phenolic content in the extracts was determined by the Folin-Ciocalteu assay. It ranged from 0.91 to 48.25 mg gallic acid/g. The antioxidant ability was measured using a free radical-scavenging activity assay using 2,2diphenyl-1-picrylhydrazyl (DPPH). The methanolic extracts showed moderate DPPH radical-scavenging activity. Among the lichen acids, umbilicaric acid showed the highest antioxidant activity with 68.14% inhibition. Antimicrobial activity was determined by the agar diffusion method. Extracts were found to possess antimicrobial activity against some of the bacteria and yeasts tested. Gyrophoric acid was effective against six out of eight bacteria tested, but no activity was observed against the yeasts.

Plant Science, Jan 1, 2003

When seedlings of two rice (Oryza sativa L. ) cultivars were raised in sand cultures under 500 an... more When seedlings of two rice (Oryza sativa L. ) cultivars were raised in sand cultures under 500 and 1000 mM Pb(NO 3 ) 2 in the medium, lengths as well as weights of roots and shoots decreased with increase in Pb concentration. Pb-treated seedlings showed elevated levels of lipid peroxides with a concomitant increase in the activities of the enzymes superoxide dismutase (SOD), guaiacol peroxidase, ascorbate peroxidase and glutathione reductase compared to controls. Though Pb was readily absorbed by growing seedlings, its localization was greater in roots than shoots. The level of Pb accumulation in seedlings was far higher than the supplied one. Seedlings grown for 5 Á/20 days in presence of 1000 mM Pb(NO 3 ) 2 showed about 21 Á/177% increase in the level of thiobarbituric acid reacting substances (TBARS) in shoots indicating enhanced lipid peroxidation compared to controls. With increase in the level of Pb treatment in situ peroxidases showed more increase in activity than SOD. Under both controls as well as Pb treatments roots maintained higher activity of these enzymes than shoots. About 87 Á/100% increase in SOD activity, 1.2 Á/5.6 times increase in guaiacol peroxidase activity and 1.2 Á/1.9 times increase in ascorbate peroxidase activity was observed in the roots of seedlings grown for 15 days in presence of 1000 mM Pb in the medium. Under similar treatment conditions about 128 Á/196% increase in glutathione reductase activity was recorded in roots and 69 Á/196% increase in shoots compared to control grown seedlings. Pb treatment resulted in a decline in catalase activity in roots whereas in shoots catalase activity increased in seedlings grown at moderately toxic Pb (500 mM) level whereas a highly toxic Pb (1000 mM) level led to a marked inhibition in enzyme activity. Two catalase isoforms were detected in roots and three in shoots of the seedlings. A highly toxic Pb (1000 mM) level led to decrease in the intensity of two preexisting catalase isoforms in shoots. Results suggest that Pb induces oxidative stress in growing rice plants and that SOD, peroxidases and GR could serve as important components of antioxidative defense mechanism against Pb induced oxidative injury in rice. #

Journal of experimental botany, Jan 1, 2001

Calcium (Ca 2q ) may be involved in plant tolerance to heat stress by regulating antioxidant meta... more Calcium (Ca 2q ) may be involved in plant tolerance to heat stress by regulating antioxidant metabolism oruand water relations. This study was designed to examine whether external Ca 2q treatment would improve heat tolerance in two C 3 , cool-season grass species, tall fescue (Festuca arundinacea L.) and Kentucky bluegrass (Poa pratensis L.), and to determine the physiological mechanisms of Ca 2q effects on grass tolerance to heat stress. Grasses were treated with CaCl 2 (10 mM) or H 2 O by foliar application and then exposed to heat stress (35u30 8C) in growth chambers. Some of the Ca 2q -untreated plants were maintained at 20u15 8C as the temperature control. Heat stress reduced grass quality, relative water content (RWC), and chlorophyll (Chl) content of leaves in both species, but Ca 2q treatment increased all three factors under heat stress. The Ca 2q concentration in cell saps increased with heat stress and with external Ca 2q treatment in both species. Osmotic potential increased with heat stress, but external Ca 2q treatment had no effect. Osmotic adjustment increased during short-term heat stress, but then decreased with a prolonged period of stress; it was not influenced by Ca 2q treatment. The activity of superoxide dismutase (SOD) in both species increased transiently at 12 d of heat stress and then remained at a level similar to that of the control. External Ca 2q treatment had no effect on SOD activity. The activities of catalase (CAT), ascorbate peroxidase (AP), and glutathione reductase (GR) of both species decreased during heat stress. Plants treated with Ca 2q under heat stress had higher CAT, GR and AP activities than untreated plants. Lesser amounts of malondialdehyde (MDA) accumulated in Ca 2qtreated plants than in untreated plants during extended periods of heat stress. The results suggested that exogenous Ca 2q treatment enhanced heat tolerance in both tall fescue and Kentucky bluegrass. This enhancement was related to the maintenance of antioxidant activities and a decrease in membrane lipid peroxidation, but not to the regulation of osmotic potential and osmotic adjustment.

Toxicology, Jan 1, 2002

Plant phenolic compounds such as flavonoids and lignin precursors are important constituents of t... more Plant phenolic compounds such as flavonoids and lignin precursors are important constituents of the human diet. These dietary phytophenolics have been recognized largely as beneficial antioxidants that can scavenge harmful active oxygen species including O 2 − , H 2 O 2 , OH, and 1 O 2 . Here we review our current understanding of the antioxidant and prooxidant actions of phenolics in plant cells. In plant systems, phytophenolics can act as antioxidants by donating electrons to guaiacol-type peroxidases (GuPXs) for the detoxification of H 2 O 2 produced under stress conditions. As a result of such enzymatic as well as non-enzymatic antioxidant reactions, phenoxyl radicals are formed as the primary oxidized products. Until recently, phenoxyl radicals had been difficult to detect by static electron spin resonance (ESR) because they rapidly change to non-radical products. Application of Zn exerts spin-stabilizing effects on phenoxyl radicals that enables us to analyze the formation and decay kinetics of the radicals. The ESR signals of phenoxyl radicals are eliminated by monodehydroascorbate radical (MDA) reductase, suggesting that phenoxyl radicals, like the ascorbate radical, are enzymatically recycled to parent phenolics. Thus, phenolics in plant cells can form an antioxidant system equivalent to that of ascorbate. In contrast to their antioxidant activity, phytophenolics also have the potential to act as prooxidants under certain conditions. For example, flavonoids and dihydroxycinnamic acids can nick DNA via the production of radicals in the presence of Cu and O 2 . Phenoxyl radicals can also initiate lipid peroxidation. Recently, Al, Zn, Ca, Mg and Cd have been found to stimulate phenoxyl radical-induced lipid peroxidation. We discuss the mechanism of phenoxyl radical prooxidant activity in terms of lifetime prolongation by spin-stabilizing agents.

… Plants, XXIII IHC 306, Jan 1, 1990

Gas chromatography and GC-MS analyses The running conditions for the GLC analysis have been previ... more Gas chromatography and GC-MS analyses The running conditions for the GLC analysis have been previously described [Deans and Svoboda, 1990], using a Carbowax 20M vitreous silica capillary column fitted in a United Technologies Packard model 439 with Hewlett Packard ...

Journal of Applied Microbiology, Jan 1, 2000

H .J .D . DO RM A N A ND S .G . D E AN S. 2000. The volatile oils of black pepper [Piper nigrum L... more H .J .D . DO RM A N A ND S .G . D E AN S. 2000. The volatile oils of black pepper [Piper nigrum L. (Piperaceae)], clove [Syzygium aromaticum (L.) Merr. & Perry (Myrtaceae)], geranium [Pelargonium graveolens L'Herit (Geraniaceae)], nutmeg [Myristica fragrans Houtt. (Myristicaceae), oregano [Origanum vulgare ssp. hirtum (Link) Letsw. (Lamiaceae)] and thyme [Thymus vulgaris L. (Lamiaceae)] were assessed for antibacterial activity against 25 different genera of bacteria. These included animal and plant pathogens, food poisoning and spoilage bacteria. The volatile oils exhibited considerable inhibitory effects against all the organisms under test while their major components demonstrated various degrees of growth inhibition.

Journal of agricultural …, Jan 1, 1998

Agricultural and Environmental Chemistry: crop protection chemistry, addressing synthesis combine... more Agricultural and Environmental Chemistry: crop protection chemistry, addressing synthesis combined with testing of new materials, environmental behavior and fate, residues, and mechanism of effects on both target and nontarget organisms.

Journal of Agricultural and Food Chemistry, Jan 1, 1997

Hydroxycinnamic acid compounds are an important source of antioxidants due to their ubiquitous oc... more Hydroxycinnamic acid compounds are an important source of antioxidants due to their ubiquitous occurrence in the plant kingdom and their characteristic activities. In this study, we compared the antioxidative and free radical scavenging activities of caffeic acid (CA), caffeic acid ...