Foliar-Applied Glutathione Mitigates Cadmium-Induced Oxidative Stress by Modulating Antioxidant-Scavenging, Redox-Regulating, and Hormone-Balancing Systems in Brassica napus.

The antioxidant glutathione (GSH) mitigates adverse physio-metabolic effects and defends against abiotic types of stress, such as cadmium (Cd) stress. However, its function and role in resisting Cd phytotoxicity by leveraging plant antioxidant-scavenging, redox-regulating, and hormone-balancing systems have not been comprehensively and systematically demonstrated in the Cd-hyperaccumulating plant Brassica napus L. cv. Tammi (oilseed rape). In this study, the effects of exogenously applied GSH to the leaves of B. napus seedlings exposed to Cd (10 µM) were investigated. As a result, Cd stress alone significantly inhibited growth and increased the levels of reactive oxygen species (ROS) and the bioaccumulation of Cd in the seedlings compared with those in unstressed controls. Furthermore, Cd stress induced an imbalance in plant stress hormone levels and decreases in endogenous GSH levels and GSH redox ratios, which were correlated with reductions in ascorbate (AsA) and/or nicotinamide adenine dinucleotide phosphate (NADPH) redox states. However, the exogenous application of GSH to Cd-stressed B. napus seedlings reduced Cd-induced ROS levels and enhanced antioxidant-scavenging defenses and redox regulation by both increasing seedling AsA, GSH, and NADPH concentrations and rebalancing stress hormones, thereby enhancing Cd uptake and accumulation. These results demonstrate that GSH improved plant redox status by upregulating the AsA-GSH-NADPH cycle and reestablishing normal hormonal balance. This indicates that exogenously applied GSH can mitigate Cd phytotoxicity in B. napus and possibly other plants. Therefore, GSH can potentially be applied to Cd-polluted soil for plant remediation.

Ascorbate-Mediated Modulation of Cadmium Stress Responses: Reactive Oxygen Species and Redox Status in Brassica napus.

The role of ascorbate (AsA) in antioxidant defense system-associated resistance to cadmium (Cd) in oilseed rape plants has not yet been clearly demonstrated. The present study investigated the critical role of exogenous AsA on the physiological and biochemical responses of reactive oxygen species (ROS) and antioxidant scavenging defense systems in oilseed rape (Brassica napus L. cv. Tammi) seedlings exposed to Cd. Cd (10 µM) treatment led to significant reductions in plant growth; increases in the levels of superoxide anion radical, hydrogen peroxide, and malondialdehyde; and increases in Cd uptake and accumulation by the roots and shoots in hydroponically grown 10-day-old seedlings. Moreover, it reduced AsA content and AsA redox ratios, which have been correlated with reductions in glutathione (GSH) and/or nicotinamide adenine dinucleotide phosphate (NADPH) redox status. However, exogenously applying AsA to Cd-exposed seedlings decreased Cd-induced ROS, improved antioxidant defense systems by increasing AsA, GSH, and NADPH contents, and increased Cd uptake and accumulation in both roots and shoots of the plants. These results provided evidence that the enhancement in AsA redox status can be linked to an increase in the GSH and/or NADPH redox ratios through the induction of the AsA-GSH-NADPH cycle. Thus, these results suggest that exogenous AsA application to oilseed rape seedlings under Cd stress might alleviate the overall Cd toxicity by regulating the homeostasis of the AsA-GSH-NADPH cycle, which reestablishes the steady-state cellular redox status.

Exogenous Glutathione Increases Arsenic Translocation Into Shoots and Alleviates Arsenic-Induced Oxidative Stress by Sustaining Ascorbate-Glutathione Homeostasis in Rice Seedlings.

Glutathione (GSH) plays diverse roles in the physiological processes, stress defense, growth, and development of plants. This study investigated the effects of exogenous GSH on the biochemical responses of reactive oxygen species and antioxidant levels in rice (Oryza sativa L. cv. Dasan) seedlings under arsenic (As) stress. As treatment inhibited growth; increased the level of superoxide, hydrogen peroxide, and malondialdehyde; and enhanced the uptake of As by the roots and shoots in hydroponically grown 14-day-old seedlings. Furthermore, it reduced GSH content and GSH redox ratios, which have been correlated with the decrease in ascorbate (AsA) redox state. Whereas the exogenous application of GSH in As-treated seedlings reduced As-induced oxidative stress, improved antioxidant defense systems by maintaining antioxidant and/or redox enzyme homeostasis, and increased the AsA and GSH contents, the GSH application also increased the As translocation from the roots to the shoots. These results indicated that the increase in GSH redox state can be linked to an increase in the AsA redox ratio via the induction of the AsA-GSH cycle. Therefore, the results suggest that exogenous GSH application should be a promising approach to enhance As stress resistance in rice plants.

Growth-inhibition patterns and transfer-factor profiles in arsenic-stressed rice (Oryza sativa L.).

Arsenic (As) accumulation in rice owing to uptake from the soil is a critical human health issue. Here, we studied the chemical properties of As-treated soils, growth inhibition patterns of As-stressed rice plants, changes in the As content of soil and soil solutions, and the relationship between As accumulation and As transfer factor from the soil to the rice organs. Rice plants were cultivated in a greenhouse under four concentrations of As: 0 (control), 25, 50, and 75 mg kg-1. A significant positive correlation was found between available P2O5 and exchangeable K and between As concentration and available P2O5 or exchangeable K. The As concentration for 50% shoot growth inhibition was 50 mg kg-1. As levels in roots and shoots were positively correlated with the growth stages of rice. The transfer factor (TF)root/soil increased with As concentration at the tillering stage but decreased at the heading stage. TFroot/soil and TFshoot/soil were higher at the heading stage than at the tillering stage. As accumulation in the 25 mg kg-1 treatment was higher during the heading stage, whereas no difference was found at the tillering stage. As accumulation was related to plant biomass and soil As concentration. We found that As accumulation was greater at As concentrations that allowed for plant growth and development. Thus, species-specific threshold concentrations must be determined based on As phytotoxicity for the phytoremediation of As-contaminated soils. Hence, developing practical approaches for managing safe crop production in farmlands with an As contamination of 25 mg kg-1 or less is necessary.

Long-term assessment of the environmental fate of heavy metals in agricultural soil after cessation of organic waste treatments.

The current study examined the anthropogenic accumulation and natural decrease in metal concentrations in agricultural soils following organic waste application. Three common organic wastes, including municipal sewage sludge, alcohol fermentation processing sludge, and pig manure compost (PMC), were applied annually to an agricultural soil under field conditions over 7 years (1994-2000) at a rate of 12.5, 25, and 50 ton ha(-1) year(-1) and the soil accumulation of three metals of concern (Cu, Pb, and Zn) was monitored. Subsequently, organic waste amendments ceased and the experimental plots were managed using conventional fertilization for another 10 years (2001-2010) and the natural decrease in metal concentrations monitored. Although Cu and Zn concentrations in all experimental plots did not exceed the relevant guideline values (150 mg kg(-1) for Cu and 300 mg kg(-1) for Zn), significant increases in metal concentrations were observed from cumulative application of organic wastes over 7 years. For instance, PMC treatment resulted in an increase in Cu and Zn from 9.8 and 72 mg kg(-1) to 108.2 and 214.3 mg kg(-1), respectively. In addition, the natural decrease in Cu and Zn was not significant as soils amended with PMC showed only a 16 and 19 % decline in Cu and Zn concentrations, respectively, even 10 years after amendment ceased. This research suggested that more attention must be paid during production of organic waste-based amendments and at the application stage.

Consumer behaviors towards ready-to-eat foods based on food-related lifestyles in Korea.

The purpose of this study was to examine consumers' behaviors toward ready-to-eat foods and to develop ready-to-eat food market segmentation in Korea. The food-related lifestyle and purchase behaviors of ready-to-eat foods were evaluated using 410 ready-to-eat food consumers in the Republic of Korea. Four factors were extracted by exploratory factor analysis (health-orientation, taste-orientation, convenience-orientation, and tradition-orientation) to explain the ready-to eat food consumers' food-related lifestyles. The results of cluster analysis indicated that "tradition seekers" and "convenience seekers" should be regarded as the target segments. Chi-square tests and t-tests of the subdivided groups showed there were significant differences across marital status, education level, family type, eating-out expenditure, place of purchase, and reason for purchase. In conclusion, the tradition seekers consumed more ready-to-eat foods from discount marts or specialty stores and ate them between meals more often than the convenience seekers. In contrast, the convenience seekers purchased more ready-to-eat foods at convenience stores and ate them as meals more often than the tradition seekers. These findings suggest that ready-to-eat food market segmentation based on food-related lifestyles can be applied to develop proper marketing strategies.

Synthesis and antifungal activity of naphthalene-1,4-diones modified at positions 2, 3, and 5.

A series of 2-arylamino-5-hydroxy-naphthalene-1,4-diones, 3-arylamino-5-methoxy-naphthalene-1,4-diones, and 2-arylamino-3chloro-5-hydroxy-naphthalene-1,4-diones were synthesized and tested for in vitro antifungal activity against the species Candida and Aspergillus niger. Among those tested, 3-arylamino-5-methoxy-naphthalene-1,4-diones exhibited potent antifungal activity. In general, the 3-arylamino-5-methoxy-naphthalene-1,4-diones showed more potent antifungal activity than the 2-arylamino-5-hydroxy-naphthalene-1,4-diones and the 2-arylamino-3-chloro-5-hydroxy-naphthalene-1,4-diones.

Synthesis and biological evaluation of quinoxaline-5,8-diones that inhibit vascular smooth muscle cell proliferation.

A series of 6-arylamino-2,3-bis(pyridin-2-yl)-7-chloro-quinoxaline-5,8-diones were synthesized and evaluated for their inhibitory activity on the rat aortic smooth muscle cell (RAoSMC) proliferation. The quinoxaline-5,8-diones exhibited a potent antiproliferative activity. Further mechanistic study revealed that the inhibitory effect of one representative quinoxaline-5,8-dione on SMC proliferation was mediated by modulation of the extracellular signal-regulated kinase 1/2 signaling pathway in the RAoSMCs.

Synthesis and antifungal activity of 2/3-arylthio- and 2,3-bis(arylthio)-5-hydroxy-/5-methoxy-1,4-naphthoquinones.

2/3-Arylthio- and 2,3-bis(arylthio)-5-hydroxy-/5-methoxy-1,4-naphthoquinones 5-9 were synthesized and tested for in vitro antifungal activity against Candida species and Aspergillus niger. The synthesized compounds 5-9 generally showed good activities against Candida albicans and C. tropicalis. The results suggest that the 1,4-naphthoquinones 5-9 would be potent antifungal agents.

Synthesis and antifungal activity of 5,8-quinazolinedione derivatives modified at positions 6 and 7.

5,8-Quinazolinediones modified at positions 6 and 7 were synthesized and tested for in vitro antifungal activities against Candida species and Aspergillus niger. Most of 5,8-quinazolinediones 3-5 generally exhibited potent antifungal activity. 6-Arylamino-7-chloro-5,8-quinazolinediones (3) generally showed more potent antifungal activity than 7-arylthio-5,8-quinzolinediones (4) and 6,7-bis-(arylthio)-5,8-quinazolinediones (5).

Synthesis and biological evaluation of benzimidazole-4,7-diones that inhibit vascular smooth muscle cell proliferation.

A series of 6-arylamino-5-chloro-benzimidazole-4,7-diones were synthesized and tested for their inhibitory activity on the rat aortic smooth muscle cell (RAoSMC) proliferation. Among them, 6-arylamino-5-chloro-2-methyl-benzimidazole-4,7-diones exhibited potent antiproliferative activity. Benzimidazole-4,7-dione 2c activated SAPK/JNK signaling pathway in the RAoSMCs.

Synthesis and antifungal activity of 6-arylthio-/6-arylamino-4,7-dioxobenzothiazoles.

6-Arylthio-/6-arylamino-4,7-dioxobenzothiazoles were synthesized and tested for in vitro antifungal activity against Candida species and Aspergillus niger. 6-Arylamino-4,7-dioxobenzothiazoles 5 and 6 showed, in general, more potent antifungal activity than 6-arylthio-4,7-dioxobenzothiazoles 3 and 4. The 6-arylamino-substituted compounds 5 and 6 exhibited the greatest activity. In contrast, 6-arylthio-, 2-/5-methyl- or 5-methoxy-moieties of compounds 3-4 did not improve their antifungal activity significantly. The results of this study suggest that 6-arylamino-4,7-dioxobenzothiazoles would be potent antifungal agents.

Synthesis and antifungal activity of 2,5-disubstituted-6-arylamino-4,7-benzimidazolediones.

2,5-Disubstituted-6-arylamino-4,7-benzimidazolediones were synthesized and tested for in vitro antifungal activity against pathogenic fungi. Among them, 6-arylamino-5-chloro-2-(2-pyridyl)-4,7-benzimidazolediones exhibited potent antifungal activity against Candida species and Aspergillus niger.