.0 Neurodegenerative disorders: Neurodegenerative diseases constitute a vast group of chronic, progressive and heterogeneous brain disorders which are characterized by selective degeneration of subsets of neurons, or their dysfunction in specific areas of central nervous system (CNS). This gradual and progressive degeneration leads to either motor impairment or cognitive decline depending on the type of neuronal population affected. These neurodegenerative disorders include complex multifactorial pathologies such as Alzhiemer's disease (AD), Parkinson's disease (PD) and Amyotrophic Lateral Sclerosis (ALS) and monogenic disorders such as Huntington's disease (HD). Symmetric loss of neurons observed in these disorders may be due to the gene-environment interplay, although the specific causes underlying each are not clear. Both, predisposition of susceptibility genes and environmental factors are responsible and a fine interplay among these two appear to lead to the vulnerability to the disease (Migliore and Coppede, 2002). Besides fully penetrant causative genes responsible for inherited forms of neurodegenerative disorders, several susceptibility genes have been identified as risk factors for sporadic forms of these diseases. Moreover, environmental factors including pesticides, metals, head injury and infection have also been studied as potential risk factors for neurodegeneration and an interaction between environmental factors and genetic polymorphisms of metabolic enzymes has been observed (Brown et al., 2005). Oxidative damage and mitochondrial impairment have been extensively observed in neurodegenerative pathologies, since oxidative stress and mitochondrial dysfunction are the hallmark for most of the neurodegenerative disorders (Reichmann et al., 1995). Mitochondria themselves may often act as key producers of reactive oxygen species (ROS) and consequently lead to oxidative stress thereafter, thus causing neurodegeneration during ageing, which is also a risk factor for neurodegeneration.