PubMed · 5108687
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M G Robertson. 1971-06-28. Ascorbic acid and the common cold.. https://pubmed.ncbi.nlm.nih.gov/5108687/
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Ascorbic acid (AsA) is an essential nutritional component and powerful antioxidant in vegetables, and in plants, AsA levels are regulated by light. AsA levels in the leaves of Chinese chive (Allium tuberosum Rottler ex Spr), a popular vegetable, are poorly understood. Thus, this study was performed to assess the influence of light on AsA biosynthesis in chive and select related genes (AtuGGP1 and AtuGME1); in addition, bioinformatic analyses and gene expression level assays were performed. The biological information obtained for AtuGGP1 and AtuGME1 was analysed with several tools, including NCBI, DNAMAN, and MEGA11. After different light treatments were performed, the Chive AsA content and AtuGGP1 and AtuGME1 expression levels were determined. These results suggest that 1) compared with natural light, continuous darkness inhibited AsA synthesis in chives. 2) The amino acid sequences of AtuGGP1 and AtuGME1 are very similar to those of other plants. 3) The trends observed for the expression levels of AtuGGP1 and AtuGME1 were consistent with the AsA content observed in chives. Hence, we speculated that light controls AsA biosynthesis in chives by regulating AtuGGP1 and AtuGME1 expression. This study provided impactful and informative evidence regarding the functions of GGP and GME in chives.
A new series of iron chelators designed to protect tissues against iron-catalysed oxidative damage is described. These compounds are aminocarboxylate derivatives bearing pendant aromatic groups. They were designed to have a relatively low affinity for both ferrous and ferric iron and to be site-specifically oxidizable by hydrogen peroxide through intramolecular aromatic hydroxylation into species with strong iron binding capacity which do not catalyse hydroxyl radical formation. Thus, at the cellular level, oxidative injury is used to convert weak iron chelators into strong iron chelators in order to promote cell survival. The purpose of this local activation process is to minimise toxicity compared to strong iron chelators which may interfere with normal iron metabolism. Compounds within this series were evaluated in vitro in view of their capacity to undergo intramolecular hydroxylation and to protect cultured cells against oxidative injury. Results show that the intramolecular aromatic hydroxylation capacity is critically dependent upon the amino carboxylate chelating moieties and the substituents of the aromatic rings. Cell protection against oxidative injury is only observed with compounds possessing sufficient lipophilicity. The monohydroxylation product of N,N'-dibenzylethylenediamine N,N'-diacetic acid, protects cells against both H2O2 and tBuOOH toxicity with IC50's of 12 and 60 microM, respectively, in agreement with the oxidative activation concept. These results represent the first step toward the development of a new strategy to safe iron chelation for the prevention of oxidative damage.
Peroxynitrite (ONOO-), a potent oxidant formed by reaction of nitric oxide (NO.) with superoxide anion, can activate guanylyl cyclase and is able to induce vasodilation or inhibit platelet aggregation and leukocyte adhesion, via thiol-dependent formation of NO. Reaction of ONOO- with thiols is thought to proceed through formation of a S-nitrothiol (thionitrate; RSNO2) intermediate and yields low levels of S-nitrosothiols (thionitrites; RSNO), both of which are theoretical sources of NO. Kinetic analysis of NO. production after reaction of ONOO- with GSH established that NO. originates exclusively from the thionitrite GSNO. Further mechanistic investigations indicated that GSNO formation by ONOO- does not occur via one-electron oxidation mechanisms. Nitrosation of GSH could theoretically proceed via intermediate formation of the thionitrate GSNO2, which, after rearrangement to the corresponding sulfenyl nitrite (GSONO), can react with GSH to form GSNO and GSOH. However, no evidence for such a mechanism was found in experiments with NO2. or with the stable nitrothiol tert-butylthionitrate. Using high performance liquid chromatography with chemiluminescence detection, formation of H2O2 was observed after reaction of ONOO- with GSH under both aerobic and anaerobic conditions, at levels similar to the yield of GSNO, indicative of a direct nucleophilic nitrosation mechanism with elimination of HOO-. Our results indicate that ONOO- may contribute to S-nitrosation in vivo and that direct nitrosation of thiols or other nucleophilic substrates by ONOO- may represent an important and often overlooked component of NO. biochemistry.