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Free Radicals and Antioxidants
Published in Chuong Pham-Huy, Bruno Pham Huy, Food and Lifestyle in Health and Disease, 2022
Chuong Pham-Huy, Bruno Pham Huy
Some reactive sulfur species (RSS) are thiyl radical (RS•) and peroxysulfenyl radical (RSOO•). Furthermore, some ROS such as hydrogen peroxide (H2O2), ozone (O3), singlet oxygen (1O2), lipid peroxide (LOOH), and hypochlorous acid (HOCl), are not considered free radicals, and are generally called oxidants because they are more and less stable. It is the same for some RNS like nitrous acid (HNO2), dinitrogen trioxide (N2O3), and some RSS such as sulfite (SO3 –), disulfide (DSSO), and sulfenic acid (RSOH). However, these oxidants can easily lead to free radical reactions in living organisms and can yield reactive species – active free radicals (6, 15, 17–19).
Principles of Radioiodination and Iodine-Labeled Tracers in Biomedical Investigation †
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
Mrinal K. Dewanjee, Shyam A. Rao
Radioiodine can be introduced into the ring compounds containing benzene, naphthalene, or other such nuclei with primary amino groups by the Sandmeyer reaction. The primary amino group is diazotized and subsequently replaced with radioiodine (Figure 9). This technique has been used in the preparation of 131I-labeled trypan blue.64 It is essential to remove excess nitrous acid by oxidation with urea.
Inhibition of Colon Carcinogenesis*
Published in Herman Autrup, Gary M. Williams, Experimental Colon Carcinogenesis, 2019
An alternative method of inhibiting chemical carcinogenesis is to prevent the formation of the carcinogen. Vitamin C has been shown to suppress the formation of nitrosamines generated by reaction of nitrous acid with Oxytetracycline, morpholine, dimethylamine, piperazine, methylurea, and N-methylaniline.56 In a preliminary report provision of 1.2% ascorbic acid to the diet of DMH-treated SD rats reduced the colon tumor incidence to 38% compared to 64% in the unsupplemented control.47 The protective effect of Vc may be related to its ability to react directly with carcinogens,57 to block carcinogen activation,56 to suppress enzyme activities, or to enhance others as Vc does in MNNG stimulation of guanylate cyclase.58 Ascorbic acid may reverse early stages of carcinogenesis. In a human study Vc is reported to reduce the number of polyps in familial polyposis patients with multiple polyps who have undergone ileorectal anastomosis.59
Electrophysiological characterization of the activating action of a novel liposomal nitric oxide carrier on Maxi-K channels in pulmonary artery smooth muscle cells
Published in Journal of Liposome Research, 2021
Irina V. Ivanova, Mariia I. Melnyk, Dariia O. Dryn, Vitalii V. Prokhorov, Alexander V. Zholos, Anatoly I. Soloviev
To remove atmospheric oxygen, a high purity argon gas was pumped for 30 min through a liposomal emulsion of cytochrome c (100 ml) obtained after homogenization. The aim of this procedure was to prevent nitrous acid formation due to NO reaction with oxygen in the aqueous medium. After that, NO obtained in the reaction of nitric acid and metallic copper was fed into the emulsion in an argon flow. The mixture of gases was first passed through a solution of sodium hydroxide to remove the salt-forming oxides. Simultaneously, the liposome emulsion was acidified with nitric acid to pH 6.3–6.5. In this case, the liposomal cytochrome c was transformed into a reduced form (cytc3+ –NO). The transition indicator was a change in the colour of the emulsion from reddish-brown to bright pink, as well as spectral absorption peaks at 528 nm and 560 nm. To stabilize the liposomal cytochrome c, 10 mg of GSNO was added to the emulsion.
Investigating the root cause of N-nitrosodimethylamine formation in metformin pharmaceutical products
Published in Expert Opinion on Drug Safety, 2021
Nasr Eldin Hussein Nasr, Metwaly Gamel Metwaly, Eman Osama Ahmed, Ahmed Roshdy Fares, Aliaa Nabil ElMeshad
Amines may be present in a pharmaceutical manufacturing process due to a variety of reasons. The active pharmaceutical ingredient (API) (or API degradants), intermediates, or starting materials may contain secondary or tertiary amine functional groups; the use of recycled solvents like quenching dimethyl formamide with sodium nitrite; and including a manufacturing equipment that is contaminated with N-nitrosoamines. Tertiary and quaternary amines may also be added intentionally as reagents or catalysts. All of these types of amines can react with nitrous acid or other nitrosating agents to form N-nitrosamines [8–10]. Figure 2 summarizes the various causes of NDMA formation in pharmaceutical products.
S-Nitrosoglutathione formation at gastric pH is augmented by ascorbic acid and by the antioxidant vitamin complex, Resiston
Published in Pharmaceutical Biology, 2018
Vitali I. Stsiapura, Ilya Bederman, Ivan I. Stepuro, Tatiana S. Morozkina, Stephen J. Lewis, Laura Smith, Benjamin Gaston, Nadzeya Marozkina
Our data suggest that the increased GSNO formation at pH range of 2.5–4.5 in the presence of ascorbate could most likely be explained by O-nitrosoascorbic acid formation that serves as a donor–acceptor for NO+ (Figure 7). The AA does not appear to act through reduction of oxidized thiol (Figure 4). With regard to the possibility that GSNO could be formed in the stomach, our data confirm that GSNO is formed from physiological levels of GSH and nitrite in the aqueous solutions at different pH and in human gastric fluid. Reaction of nitrous acid HNO2 with GSH is responsible for the GSNO formation and its rate increases with lower pH due to the protonation of nitrite ion: