RADIOPROTECTIVE AND ANTIOXIDANT PROPERTIES OF INDIAN MEDICINAL PLANT, Terminalia arjuna

Using rat liver mitochondria as model systems, we examined the radioprotective and antioxidant effects of the Indian medicinal plant Terminalia arjuna. Various sohxlet fractions of the bark and the medicinal formulation arjunsal besides an active ingredient, baicalein, were examined for their ability to protect both rat liver mitochondria and cardiac homogenate against radiation and oxidative stress apart from their ability to scavenge radicals and for ferric reducing/antioxidant power. Among the various extracts from arjunsal the ones from organic solvents were found to be the most effective in DPPH, ABTS and FRAP assays. In T. arjuna bark, the methanolic extract showed the highest antioxidant activity. Radioprotection studies also showed that the methanolic extract was the most effective. Baicalein showed antioxidant as well as radioprotective activity. To look at the possible mechanisms for the observed antioxidant/radioprotective effects pulse radiolysis was performed to examine the reactions of baicalein with various radiation-related and biologically relevant reactive species such as hydroxyl radical (OH), azide radical (N3), lipid peroxyl radical (LOO), trichloro methyl operoxyl radical (CCl3O2) and thiyl (RS) radical. Baicalein reacts with these radicals at almost diffusion controlled rates. The bimolecular rate constants for the reaction of these radicals were in the order of 10 dmmols. The above results indicate that various preparations from T. arjuna and its component baicalein have significant radioprotective and antioxidant activities and the ability to react with radiation-derived or radiation-related reactive species may be the factor responsible.