Antioxidants Versus Reactive Oxygen Species – A Tug of War for Human Benefits? 176 Ashwell R. Ndhlala, Bhekumthetho Ncube, and Johannes van Staden Contents Introduction: Definitions and Overview of ROS and ANTs ................................. 3988 ANTs Versus ROS: Benefiting Human Survival ............................................. 3990 Biological Activity of ANTs .................................................................. 3991 What Is in it for Humans? ..................................................................... 3993 The Benefits from ROS .................................................................... 3993 The Tilted Balance and the Benefits of ANTs ............................................ 3994 ANTs as a Double-Sided Sword ........................................................... 3995 Pharmacokinetic Parameters ................................................................... 3997 Bioavailability .................................................................................. 3997 Conclusions .................................................................................... 3999 References ...................................................................................... 3999 Abstract The complex network of metabolic processes and reactions within the integrated system of aerobic life hinges largely on the presence of oxygen. Utilization of this highly reactive molecule in biological systems under normal metabolism and xenobiotic exposure inevitably results in the generation and accumulation of reactive oxygen species (ROS), which may lead to oxidative stress and hence damage to key molecular species. Oxidative damage has been implicated as the key factor in accelerated pathogenesis of a number of human diseases including cardiovascular, inflammatory, cancer, autoimmune, and neurodegenerative diseases. ROS also play defined functions through redox modifications of A.R. Ndhlala • B. Ncube • J. van Staden (*) Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal Pietermaritzburg, Scottsville, South Africa e-mail: ndhlala@ukzn.ac.za; 209522727@ukzn.ac.za; rcpgd@ukzn.ac.za I. Laher (ed.), Systems Biology of Free Radicals and Antioxidants, DOI 10.1007/978-3-642-30018-9_181, # Springer-Verlag Berlin Heidelberg 2014 3987