NISCAIR Online Periodicals Repository Collection: IJBB Vol.48(5) [October 2011]

Effects of kale (Brassica oleracea L. var. acephala DC) leaves extracts on the susceptibility of very low and low density lipoproteins to oxidation

Wed, 28 Sep 2011 22:58:59 GMT

Title: Effects of kale (Brassica oleracea L. var. acephala DC) leaves extracts on the susceptibility of very low and low density lipoproteins to oxidation

Authors: Kural, Birgül Vanizor; Küçük, Nurçin; Yücesan, Fulya Balaban; Örem, Asim

Abstract: Of Brassicaceous plants, kale (Brassica oleraceae L. var. acephala DC) contains polyphenols, flavonoids, isoflavones and glucosinolates and so has antioxidant and anticarcinogenic properties. Antioxidants inhibit negative effects of free radicals and may, therefore, protect tissues against oxidative damage. Oxidation of lipoproteins is a key event in the development of atherosclerosis. In the current study, the levels of total phenolic and flavonoid contents and total antioxidant capacity of methanolic and aqueous extracts of kale leaves were determined. In addition, the susceptibility of isolated lipoproteins — very low density lipoprotein (VLDL) and low density lipoprotein (LDL) to the Cu²⁺-induced oxidation with various concentrations of metanolic and aqueous extracts was evaluated as t-lag values. Although aqueous extract had higher total antioxidant capacity, methanolic extract had higher total phenolic and flavonoid content (P<0.05). On the other hand, both extracts inhibited lipid peroxidation in both isolated VLDL and LDL. Inhibitory effect of extracts or increasing t-lag values, mainly in methanolic extract was found to be related to increasing the concentration of extracts. It was concluded that because of high antioxidant capacity and phenolic content, kale showed a protective effect on the oxidation of lipoproteins. Therefore, it may be speculated that kale consumption may play an important protective role in the cardiovascular and other related diseases resulting from imbalance of oxidant and antioxidant status.

Page(s): 361-364

Role of chlorophyllase in chlorophyll homeostasis and post-harvest breakdown in Piper betle L. leaf

Wed, 28 Sep 2011 22:58:59 GMT

Title: Role of chlorophyllase in chlorophyll homeostasis and post-harvest breakdown in Piper betle L. leaf

Authors: Gupta, Supriya; Gupta, Sanjay Mohan; Kumar, Nikhil

Abstract: Piper betle L., a dioecious shade-loving perennial climber is one of the important Pan-Asiatic plants. More than hundred landraces having marked variation in leaf chlorophyll (Chl) content are in cultivation in India. In this study, role of chlorophyllase (Chlase) in Chl homeostasis and post-harvest breakdown was investigated in two contrasting P. betle landraces Kapoori Vellaikodi (KV) with light green and Khasi Shillong (KS) with dark green leaves. The two landraces showed negative correlation between Chl content and Chlase activity in fresh as well as stored leaves. Accumulation of chlorophyllide a (Chlid a) was correlated with the level of Chlase activity, which was higher in KV than KS. The overall response of abscisic acid (ABA) and benzylaminopurine (BAP) was similar in KV and KS, however, the time-course was different. ABA-induced Chl loss was accompanied by rise in Chlase activity in KV and KS and the delay in Chl loss by BAP was accompanied by reduction in Chlase activity. While there were significant differences in Chlase activity in KV and KS, only minor differences were observed in the enzyme properties like pH and temperature optima, K_m and V_max. No landrace-related differences were observed on the effect of metal ions and functional group reagents/amino acid effectors on Chlase activity. These results showed that despite significant differences in Chl content and Chlase activity between landraces KV and KS, the properties of Chlase were similar. The findings show that in P. betle Chlase is involved in Chl homeostasis and also in Chl degradation during post-harvest storage and responds to hormonal regulations. These findings might be useful in predicting the stability of Chl during post-harvest storage and also the shelf-life in other P. betle landraces.

Page(s): 353-360

Role of antioxidant and anaerobic metabolism enzymes in providing tolerance to maize (Zea mays L.) seedlings against waterlogging

Wed, 28 Sep 2011 22:58:59 GMT

Title: Role of antioxidant and anaerobic metabolism enzymes in providing tolerance to maize (Zea mays L.) seedlings against waterlogging

Authors: Chugh, Vishal; Kaur, Narinder; Gupta, Anil K

Abstract: The present investigation was undertaken to identify the possible mode of mechanism that could provide tolerance to maize (Zea mays L.) seedlings under waterlogging. Using cup method, a number of maize genotypes were screened on the basis of survival of the seedlings kept under waterlogging. Two tolerant (LM5 and Parkash) and three susceptible (PMH2, JH3459 and LM14) genotypes were selected for the present study. Activities of antioxidant and ethanolic fermentation enzymes and content of hydrogen peroxide (H₂O₂)_,glutathione and ascorbic acid were determined in roots of these genotypes after 72 h of waterlogging. Waterlogging treatment caused decline in activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) in all the genotypes. However, only susceptible genotypes showed slight increase in glutathione reductase (GR) activity. Significant reduction in APX/GR ratio in susceptible genotypes might be the cause of their susceptibility to waterlogging. The tolerant seedlings had higher GR activity than susceptible genotypes under unstressed conditions. Stress led to decrease in H₂O₂ and increase in glutathione content of both tolerant and susceptible genotypes, but only tolerant genotypes exhibited increase in ascorbic acid under waterlogging conditions. In the tolerant genotypes, all the enzymes of anaerobic metabolism viz. alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH) and pyruvate decarboxylase (PDC) were upregulated under waterlogging, whereas in susceptible genotypes, only ADH was upregulated, suggesting that efficient upregulation of entire anaerobic metabolic machinery is essential for providing tolerance against waterlogging. The study provides a possible mechanism for waterlogging tolerance in maize.

Page(s): 346-352

Kinetic properties of cell wall bound superoxide dismutase in leaves of wheat (Triticum aestivum L.) following stripe rust (Puccinia striiformis) infection

Wed, 28 Sep 2011 22:58:59 GMT

Title: Kinetic properties of cell wall bound superoxide dismutase in leaves of wheat (Triticum aestivum L.) following stripe rust (Puccinia striiformis) infection

Authors: Asthir, Bavita; Koundal, A; Bains, N S

Abstract: Stripe rust (Puccinia striiformis f.sp. tritici) is the most devastating disease of wheat (Triticum aestivum L.) accounting huge economical losses to the industry worldwide. HD 2329 was a widely grown wheat cultivar which had become highly susceptible to stripe rust and was used to understand the biochemical aspects of the host pathogen interaction through characterization of superoxide dismutase (SOD). In the present study, two types of SOD, ionically or covalently bound to the particulate fraction were found in the stripe rust infected and uninfected wheat leaves of susceptible cultivar HD 2329. Cell walls of leaves contained a high level of SOD, of which 41-44% was extractable by 2 M NaCl and 10-13% by 0.5% EDTA in infected and uninfected leaves. The NaCl-released SOD constituted the predominant fraction. It exhibited maximum activity at pH 9.0, had a K_m value of 1.82-2.51 for uninfected and 1.77-2.37 mM for infected, respectively with pyrogallol as the substrate, and a V_max of 9.55-21.4 and 12.4-24.1 A min^-1g^-1FW. A temperature optimum of 20^oC was observed for SOD of both uninfected and infected leaves. SOD showed differential response to metal ions, suggesting their distinctive nature. Inhibition of wall bound SOD by iodine and its partial regeneration of activity by mercaptoethanol suggested the involvement of cysteine in active site of the enzyme. These two forms showed greater differences with respect to thermodynamic properties like energy of activation (E_a) and enthalpy change (H), while entropy change (S) and free energy change (G) were similar. The results further showed that pathogen infection of the leaves of susceptible wheat cultivar induced a decrease in the SOD activity and kinetics which might be critical during the response of plant cells to the infection.

Page(s): 341-345