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Ascorbic Acid
Published in Ruth G. Alscher, John L. Hess, Antioxidants in Higher Plants, 2017
The monodehydroascorbate radical spontaneously disproportionates to ascorbate and dehydroascorbate (105Μ-1 s-1 at pH 7.0). Monodehydroascorbate radicals are also directly reduced to ascorbate by the action of NAD(P)H-dependent monodehydroascorbate reductase11,27 (EC 1.6.5.4), as shown in Figure 1. Dehydroascorbate is also highly unstable at pH values greater than pH 6.0. The carbon chain is cleaved to products such as tartrate and oxalate,3 and may decompose to yield toxic derivatives. Part of the oxalate formed in plant tissues appears to arise from ascorbate. To prevent loss of the ascorbate pool following oxidation, the chloroplast contains efficient mechanisms of recycling both monodehydroascorbate and dehydroascorbate, and these ensure that the ascorbate pool is maintained largely in the reduced form (Figure 1). Reduced glutathione (GSH), which is present in chloroplasts in millimolar concentrations, will nonenzymically reduce dehydroascorbate back to ascorbate at pH values greater than pH 7.0 (Reaction 4): 2GSH + dehydroascorbate → GSSG + ascorbate (4)
Evaluation of mature miR398 family, expression analysis and the post-transcriptional regulation evidence in gamma-irradiated and nitrogen-stressed Medicago sativa seedlings
Published in International Journal of Radiation Biology, 2019
Mohammed Javed, Anshika Sinha, Lata Israni Shukla
The normal growth of sessile plants requires their sustenance under various biotic and abiotic stress which is associated with the formation of free radicals. The ionization radiation-induced responses in plants are an important area of research (Esnault et al. 2010). The increase in the damage caused by the radiation and formation of reactive oxygen species (ROS) could be used to quantify the damage. The ROS-related enzymatic antioxidant responses include superoxide dismutase (SOD), ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase (GR) and catalase are also reported for radiation damage (Caverzan et al. 2016). Several environmental stress factors act simultaneously on plants causing an imbalance in the ROS production and its detoxification, leading to oxidative stress (Miller et al. 2010; Li et al. 2017). Biotic stress which includes interaction with microbes and other pathogens and abiotic stress such as nutrient stress, salt stress, drought stress, radiation stress often leads to oxidative burst (Zhu et al. 2011).
Atriplex halimus aqueous extract abrogates carbon tetrachloride-induced hepatotoxicity by modulating biochemical and histological changes in rats
Published in Archives of Physiology and Biochemistry, 2020
Kheira Slama, Mahieddine Boumendjel, Faiza Taibi, Amel Boumendjel, Mahfoud Messarah
Ascorbic acid (vitamin C) is a potent scavenger of ROS in plasma and liver cells, which destroys free radicals in combination with GSH (George 2003). Decreased level of this antioxidant parameter seen in the hepatic tissue of CCl4 treated group compared to the control. The decline in GSH level contribute to the decrease in ascorbate concentration in liver which were induced to the accumulation of free radicals in liver cells (Anand et al. 2012). Rats pretreated with AHAE could regenerate the amount of ascorbic acid enzymatically using monodehydroascorbate reductase principally at the expense of reduced glutathione, or non-enzymatically by spontaneous dismutation after scavenging of the ROS with the plant extract (George 2003).