Abstract

OVERVIEW ON THE BIOLOGICAL ROLE OF FREE RADICALS

Prof. Michele Vitolo*

Abstract

Free radicals (FR) - such as nitric oxide (NO), hydroxyl (OH●), superoxide (O2 -) and oxygen singlet (*O2) - are highly reactive molecules with at least one unpaired electron in their structures. The mechanism of FR action is based on propagation chain reaction, in which the radical regenerates many times. In either a chemical reactor or a human body, FR propagation must be under strict control, otherwise the chemical product becomes inappropriate to use or the body becomes sick. On one hand, FR action can be beneficial to the organism when it controls pivotal physiologic responses such as phagocytosis, enzyme activation (guanylate cyclase in the synthesis of cyclic guanosine monophosphate, for instance), and synapses potentiation of hippocampus neurons. On the other hand, when the FR accumulates uncontrollably an oxidative stress inside the organism leads to a series of diseases (cancer, atherosclerosis, heart failure, and degeneration of membranes). In the organism, FR can be neutralized by enzymes (superoxide dismutase, catalase, and glutathione reductase) and or by Antioxidants (vitamins A, C and E, Uric acid, melatonin etc.).

Keywords: Free radicals, oxygen radicals, hydroxyl radical.