Review Article ANTIOXIDANT PROPERTIES OF SOME PHYTOCOMPOUNDS OF SELECTED MEDICINAL PLANTS

Free radicals like reactive oxygen species (ROS) and reactive nitrogen species (RNS) are formed in living organisms and has both beneficial and deleterious role. Moderate concentrations of free radicals are involved in physiological functions whereas excess production is highly toxic to cells resulting in oxidative stress. Free radicals have been implicated in the pathology of various human diseases like diabetes, cancer, inflammation, atherosclerosis, neurodegenerative diseases, aging process, etc. The excess ROS/RNS formed are effectively removed from our body by antioxidant defense systems. Antioxidants are emerging as both prophylactic and therapeutic agents. They are produced either endogenously or received exogenously and include both enzymatic and non-enzymatic antioxidants. Antioxidants act in several ways including scavenging reactive oxygen species or their precursors, inhibiting ROS formation and lipid peroxidation, chelating metal ions needed for catalysis of ROS generation and reducing ability. Various in vitro methods have been developed to evaluate the antioxidant activity of compounds. The present article briefly reviews i) the generation and activities of ROS and RNS ii) oxidative damage and diseases caused by free radicals iii) defense mechanisms against free radicals iii) some medicinal plants reported to possess antioxidant activity and iv) the different in vitro antioxidant screening models