Home / Oral Medicine / 5.Antioxidants


  • Formation of free radicals in biological systems revolves around  the oxygen; these free radicals involving oxygen named as reactive or reduced oxygen species.
  • Oxygen % in dry air is 21%; 2nd most abundant element in the atmosphere (Nitrogen 78%).
  • Amount in air is negligible when compared with oxygen present as a part of water molecule & as part of mineral reservoirs in the Earth’s crust.
  • Aerobic life uses oxygen to oxidise (burn) carbon & hydrogen rich substances to obtain the chemical & heat energy essential for life.


  • When molecules get oxidised with oxygen, the oxygen molecule itself reduced & forms intermediates; which are free radicals.
  • Molecular oxygen is an essential nutrient for nonfacultative aerobic organisms.
  • Oxygen is used in many ways, as the terminal electron acceptor in oxidative phosphorylation, in many dioxygenase reactions;
  •      – Synthesis of prostaglandins ,
  •      – Vitamin A from carotenoids,
  •      – Formation & modification of steroid hormones,
  •      – Activation and inactivation of xenobiotics, &
  •      – Carcinogens.

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