cellular damage such as lipid peroxidation or the oxidation of phospholipids and other unsaturated lipids. Peroxidation results in the breakdown of lipids and membrane function by causing loss of fluidity, lipid crosslinking, and inactivation of membrane
Michelle DaCosta and Bingru Huang
Sukhvinder Pal Singh and Zora Singh
, and bleeding or bladderiness. CI has been proposed to be an oxidative phenomenon linked to the production of ROS causing lipid peroxidation, membrane damage, and overall reduced capacity of antioxidant systems ( Hodges et al., 2004 ; Singh and Singh
Xiujie Yin, Chao Zhang, Xin Song, and Yiwei Jiang
, chlorophyll content, RWSC content, soluble protein content, and increased root electrolyte leakage and lipid peroxidation, and decreased or increased activities of antioxidant enzymes in shoots and roots of kentucky bluegrass ( Poa pratensis ), perennial
Shimon Meir, Sonia Philosoph-Hadas, Giora Zauberman, Yoram Fuchs, Miriam Akerman, and Nehemia Aharoni
Fluorescent products (lipofuscin-like compounds) of lipid peroxidation, which accumulate with age, were extracted from `Fuerte' avocado (Persea americana Mill.) peels during ripening. Fractionation and analysis of these fluorescent compounds (FCs) was carried out by an improved method, based on separation of FCs from-chlorophyll by Sep-Pak silica cartridges. A sharp rise in FCs content was found 2 days after harvest in avocado fruits stored at 22C, and ethylene enhanced this rise 3-fold on the 4th day. The accumulation of FCs preceded by at leasts days the onset of climacteric ethylene and respiration and by 2 days the decrease in fruit firmness. Moreover, a 6-foId increase in the FCs concentration occurred during 1 to 2 weeks of storage at SC, but the avocado fruits did not show any other detectable signs of ripening. These results suggest that lipid peroxidation may be regarded as one of the earliest detectable processes occurring during fruit ripening. Thus, an increase of FCs in peel may be employed as a horticultural characteristic for estimating initiation of ripening in avocado fruit.
Polyamines are effective scavengers of activated oxygen free radicals produced by lipoxygenase (LOX) and phospholipase-D (PL-D). Activated oxygen free radicals cause peroxidative damage to membranes and hasten senescence. Exogenous polyamine spermidine (SPD) compared to spermine (SPM) at 1 mM or no polyamine was an effective inhibitor of honey dew (Cucumis melo L. var. inodorus) membrane peroxidation, as determined by malondialdehyde (MDA), following dark incubation for 6 or 48 hours of fully abscised fruit hypodermal mesocarp tissue. MDA levels in SPD-treated tissue was lowest in both 6 and 48 hours compared to SPM or no polyamine. SPD was effective in slowing lipid peroxidation as MDA was highly negatively correlated with the loss in total chlorophyll, plasma membrane H+ pumping ATPase activity, and microsomal phospholipid content (r = -0.89, -0.64 and -0.57, respectively). Both LOX and PL-D enzyme activities were not correlated with the total chlorophyll and microsomal membrane phospholipid losses or MDA levels, demonstrating that these enzymes act indirectly in the degradation of membranes through the production of lipid peroxidating free radicals. The results also demonstrate that the effect of polyamines as anti-senescence compounds is through direct inhibition of lipid peroxidation and not by affecting LOX or PL-D free radicle production.
Essaid Ait Barka, Siamak Kalantari, and Joseph Arul
Fresh fruit and vegetables are highly perishable because of their active metabolism during the postharvest phase. Previous studies showed that hormic dose of UV cause a delay in the senescence of tomato fruit by about 7 days. The objective of this study was to elucidate whether UV acts on the cell membrane in producing the phenomenon of delayed senescence, since it is known that UV radiation can provoke photooxidation of membrane lipids. Membrane lipid peroxidation was studied in tomato fruit (Lycopersicon esculentum Mill cv. Trust) treated by hormic UV dose, and was followed by assaying products of lipid oxidation during the storage period. We observed the production of lipofuscin-like compounds, malondialdehyde, aldehydes, pentane, ethane, and hydrogen peroxide within few days of the treatment. An increase in the efflux of electrolytes (total, potassium, and calcium) was also observed. An immediate increase in the level of these products of oxidation supports the hypothesis that UV radiation induces membrane lipid peroxidation. However, beyond 5 to 7 days after treatment, the production of oxidation products and electrolyte leakage were lower than the control fruits. Thereafter, the level of products of lipid oxidation associated with senescence was higher in control fruits than in treated ones. Results suggest that the initial oxidation stress by the exposure to UV led to biochemical reactions inducing the production of stress compounds, such as polyamines, which are non specific antioxidants. Consequently, a delay in the senescence was observed.
Shimon Meir, Sonia Philosoph-Hadas, and Nehemia Aharoni
A newly developed rapid and convenient method was used for fractionation and analysis of fluorescent compounds (FCs) formed during lipid peroxidation in parsley (Petroselinum crispum Mill.) leaves. These lipofuscin-like FCs [which arise in vivo from reaction of malondialdehyde (MDA) with amino acids] were found to increase during the senescence of detached parsley leaves, following the commencement of chlorophyll degradation and proteolysis. However, accumulation of FCs in response to exogenous ethylene coincided with the onset of chlorophyll loss and proteolysis on day 2 and was accelerated markedly later. Unlike FC accumulation, levels of aldehydes and MDA in control leaves increased more drastically during senescence, but were not affected significantly by exogenous ethylene. The results suggest that the accumulation of FCs in detached parsley leaves exposed to exogenous ethylene is an early senescence-associated process.
Na Zhang, Lu Han, Lixin Xu, and Xunzhong Zhang
activity and lipid peroxidation. Fully expanded leaf blades were excised and then wrapped in foil paper, immersed in liquid nitrogen, and stored at −20 °C until measurement was determined. Determination of enzyme activity was carried out using the method