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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).
Systematic review on activity of liposomal encapsulated antioxidant, antibiotics, and antiviral agents
Published in Journal of Liposome Research, 2022
Reshna K. R, Preetha Balakrishnan, Sreerag Gopi
Antioxidants act as a first line of defense against the free radicle damage. It has the efficiency to neutralize the free radicles. Antioxidants are substances that are able to prevent or delay the oxidative damages. Antioxidant insufficiency can be developed as a result of decreased antioxidant intake. Oxidants are reactive molecules that are produced inside and outside the body, that can react with cellular molecule and it causes healthy cell. Imbalance between oxidants and antioxidants with in body due to increased antioxidant deficiency causes oxidative stress. Increased concentration of reactive oxygen species (ROS), reactive nitrogen species (RNA), and reactive sulfur species can cause cellular damage. Antioxidants applied directly and at relatively high concentrations to cellular systems which is effective in protection against the damaging actions of ROS (Lobo et al.2010). ROS includes hydroxyl radicle (OH•), perhydroxyl radicle (HO2•), hypochlorous acid (HOCl), super oxide (O2•), hydrogen peroxide (H2O2), singlet oxygen (1O2), nitric oxide radicle (NO•), hypochloride radicle (OCl•), peroxynitrite (ONOO), and different lipid peroxides(Azat Aziz et al.2019).
Oxidative stress tolerance and antioxidant capacity of lactic acid bacteria as probiotic: a systematic review
Published in Gut Microbes, 2020
Oxygen is considered one of the critical factors affecting the survival of anaerobic aerotolerant probiotic bacteria. An aerobic environment may stimulate the production of toxic oxygen byproducts, such as ROS, reactive nitrogen species (RNS), and reactive sulfur species, in probiotic LAB.5 H2O2 produced in such a condition can react with ferrous iron (Fe2+) salts and produce the extremely toxic HO· through the Fenton reaction (Figure 1).8 HO· can damage proteins, causing a reduction in ATP and resulting in a lower energy level within the bacterial cell. HO· can also break phosphodiester bonds in DNA molecules, which leads to DNA fragmentation, and damage lipid moieties within the plasma membrane. A high steady-state concentration of O2– can increase the release of Fe2+ from proteins containing iron-sulfur clusters, thus promoting the Fenton reaction (Figure 1). These radicals directly or indirectly damage proteins, DNA, and lipids, and thus eventually lead to low cell viability and cell death (Figure 1). Endogenous production of H2O2 and further reactive oxidants has been shown to be the main cause of oxidative stress in Lactobacillus johnsonii NCC 533 during aerobic growth.4 LAB lack dedicated enzymes that can eliminate HO·, but have developed other selective strategies to limit HO· formation through eliminating H2O2 and O2–9.
High-throughput screening in multicellular spheroids for target discovery in the tumor microenvironment
Published in Expert Opinion on Drug Discovery, 2020
Blaise Calpe, Werner J. Kovacs
Redox-regulated processes are positioned at the interface between genome-coded structure/function relationships and their adaptation to the availability of oxygen [80]. The redox potential is a measure of how oxidative or reductive an environment is, and via modulation of the oxidation state of proteins it plays an important role in controlling pathway activation in a cell. Redox changes are often accompanied by changes in biochemical reactions related to cellular metabolism and signaling [81]. Redox signals are transduced via reactive oxygen species (ROS), primarily hydrogen peroxide (H2O2), reactive nitrogen species (RNS), and reactive sulfur species (RSS). ROS generation, signaling, and regulation are modified in cancer to favor its survival, growth, and progression [81]. The signaling properties of particular oxidants are primarily sensed and mediated by protein thiols that are specifically and reversibly modified by oxidation, thereby switching the protein between different conformational and functional states.