Aging is characterized by a progressive decline in the efficiency of biochemical and physiological processes, the functional maintenance of tissue homeostasis and an increasing susceptibility to diseases. Aging is a multifactorial process, which is genetically determined and influenced epigenetically by environment. 1 In recent years it has been well known that oxidative stress may play important roles in elderly health and, in particular, there is increasing evidence that aging might be caused by the potential and harmful effects of an accumulation of oxidative damage caused by reactive species (RS, in particular reactive oxygen species or ROS and reactive nitrogen species RNS). This evidence is supported by the "free radical theory of aging" proposed by Harman. 2