Oxygen-derived free radical scavengers

Atalla, S.L., Toledo-Pereyra, L.H., MacKenzie, G.H. and Cederna, J.P. (1985). Influence of oxygen derived free radical scavengers on ischaemic livers. Transplantation 40, 584-590. 

Salim, A.S. (1991). Role of oxygen-derived free radical scavengers in the treatment of recurrent pain produced by chronic pancreatitis. A new approach. Arch. Surg. 126, 1109-1114. 

Salim, A.S. (1992b). Use of scavenging oxygen-derived free radicals to protect rat gainst aspirin- and ethanol-induced erosive gastritis. J. Pharm. Sci. 81, 943-946. 

Salim, A.S. (1992h). Oxygen-derived free-radical scavengers prolong survival in gastric cancer. Chemotherapy 38, 135-144. 

Ascorbic Acid (AA). Experimental (SI, S7, S24) and clinical (B13, B17) studies have provided some evidence for the concept that oxidative stress is the common pathway for the initiation of AP (B14). The most abundant endogenous antioxidant in the aqueous phase is ascorbic acid (AA), a bioactive form of vitamin C, which scavenges oxygen-derived free radicals produced by activated neutrophils and the hypoxanthine-xanthine oxidase system (D12). Scott et al. 

Depletion of GSH results in enhanced lipid peroxidation, and excessive lipid peroxidation can cause increased GSH consumption. In contrast, a rise in gastric SH levels limits the production of oxygen-derived free radicals, and could be related with cellular protection [217]. In addition to free-radical scavenging activity, SH compounds, as well as PG, may maintain a good blood flow that allows the energydepen-dent rapid restitution to cover initial epithelial surface damage [218,219]. 

There are multiple mechanisms of depolymerization, since many of the dialdehyde derivatives are highly susceptible to alkah-catalyzed -elimination, even at moderate temperatures and pH values. Moreover, the degradation of polysaccharide chains caused by free radicals may occur [22, 23]. Periodate itself is unstable and decomposes over time to form radicals, especially in the presence of light. Oxidations are therefore preferentially carried out in the dark and in the absence of oxygen, using freshly prepared periodate solutions. Also, small amounts of trace metals should be removed as they can also catalyse the formation of free radicals. It has been demonstrated that presence of free radical scavenges such as 1-propanol reduces the extent of depolymerization, and it has therefore been routinely added during oxidation, typically at concentrations around 10 % (v/v) [16]. 

Based on the accumulated experimental evidence we can summarize by saying that HALS protect polymers by a combined mechanism where the principal activities are free radical scavenging, hydroperoxide deactivation, and formation of charge transfer complexes with oxygen. The stabilization action of HALS can be adversely affected by some other substances, like organic thioether costabilizers, halogen flame retardants, or an acidic environment. Several N-substituted HALS derivatives have... 

In vitro experimental systems suggest that flavonoids can scavenge oxygen-derived free radicals exert antiinflammatory, antiallergic, and antiviral effects and have anticarcinogenic properties. 

WETTASiNGHE M and SHAHiDi F (1999) Evening Primrose Meal A source ofnatural antioxidants and scavenger of hydrogen peroxide and oxygen-derived free radicals, JAgric Food Chem, 47, 1801-12. 

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