Singlet oxygen in biological systems

A further role has been attributed to (Cu,Zn)-SOD the quenching of singlet oxygen. This raises, moreover, the question of the unlikely production of singlet oxygen in biological systems by non-photochemical means. 

N.I. Krinsky (1983). Singlet oxygen in biological systems. Trends Biochem. Sci., 2, 35-38. 

Cadenas, F. and Sies, H. (1984). Low-level chemiluminescence as an indicator of singlet molecular oxygen in biological systems. Methods in Enzymology 105 221 231. 

Oxygenation Reactions and Singlet Oxygen 4.3.1 Photosensitized Oxygenations in Biologic Systems... 

Consequently, the antioxidant activity of GA in biological systems is still an unresolved issue, and therefore it requires a more direct knowledge of the antioxidant capacity of GA that can be obtained by in vitro experiments against different types of oxidant species. The total antioxidant activity of a compound or substance is associated with several processes that include the scavenging of free radical species (eg. HO, ROO ), ability to quench reactive excited states (triplet excited states and/ or oxygen singlet molecular 1O2), and/or sequester of metal ions (Fe2+, Cu2+) to avoid the formation of HO by Fenton type reactions. In the following sections, we will discuss the in vitro antioxidant capacity of GA for some of these processes. 

Foote, C., Photosensitized oxidation and singlet oxygen conseqnences in biological systems, in Free Radicals in Biology, Pryor, W.A., Ed., Academic Press, New York, 1976. 

Girotti, AW and Korytowski, W, 2000. Cholesterol as a singlet oxygen detector in biological systems. Methods Enzymol 319, 85-100. 

Unfortunately, no more work has been done in this field. However, since amino compound degradation by singlet oxygen may play a role in biological systems, for example in photodynamic effects ( ), these reactions will probably obtain more attention in the future. 

There was also unequivocal proof that no superoxide at all was generated during this chemical reaction. Thus, this result supports earlier observations of a direct singlet oxygen generation in biological systems avoiding the pathway via superoxide. 

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