Background: Neurodegeneration is a condition in which progressive loss of function and structure of neurons occurs. Several lines of evidence suggest that oxidative stress has a central role in neurodegenerative diseases. Objective: The aim was to survey molecular mechanisms underlying the involvement of oxidative stress in developing different neurodegenerative diseases. Methods: Original and review articles were retrieved through a PubMed and Google scholar search (from 1989 to 2015) using the following key words: “oxidative stress”, “nerve degeneration” and “neurodegenerative diseases”. Results: A comprehensive analysis of the obtained articles confirmed strong involvement of oxidative stress in the pathophysiology of neurodegenerative diseases through a variety of mechanisms including induction of oxidation of nucleic acids, proteins and lipids, formation of advanced glycation end products, mitochondrial dysfunction, glial cell activation, amyloid β deposition and plaque formation, apoptosis, cytokine production and inflammatory responses, and proteasome dysfunction. Conclusion: Regarding the pivotal role of oxidative stress in neurodegeneration, modulation of free radical production or alleviating their harmful effects can be considered as a potential therapeutic strategy for preventing and controlling neurodegenerative diseases. Accordingly; boosting endogenous antioxidant capacity besides providing exogenous sources of antioxidants merits future research in order to discover new therapeutic agents.

The essential oils of different parts of Juniperus communis. subsp. hemisphaerica. (Presl) Nyman (Cupressaceae) and Juniperus oblonga. M. B. were examined for their potential radical scavenging activity. The compositions of the essential oils of these plants were studied qualitatively and quantitatively by GC and GC-MS. The main components of the essential oils as well as positive controls were subjected to antioxidant testing. A rapid evaluation for antioxidants, using two TLC screening methods, showed that all tested oils and their main components have antioxidant activity. The abilities of the volatile oils to act as nonspecific donors for hydrogen atoms for electron were checked in the diphenylpicrylhydrazyl (DPPH) assay. In the DPPH assay, the strongest effect among the essential oils was measured for the oil of leaves of male J. communis. subsp. hemisphaerica. at a concentration of 4 µL/mL (24.0%) In the deoxyribose degradation assay, the essential oils, pure components, and positive controls were tested at different concentrations. Most of the tested compounds showed some antioxidant effects. The fruit oil of J. oblonga. has the strongest effect among the tested volatile oils. The deoxyribose assay was modified in three different ways to assess whether the oils exhibited site-specific effects. The results of the current study, which demonstrate the DPPH scavenging activity of the essential oils of the of leaves of male J. communis. subsp. hemisphaerica. and the OH radical scavenging effects of the fruit oil of J. oblong. suggest the use of these two essential oils in very low concentrations for preserving food materials.