Leaf extract of cracker plant ( Ruellia tuberosa Linn) induces metal chelating activity and DNA strands break: implications for its antioxidant-prooxidant property.

Ruellia tuberosa Linn (cracker plant) of Acanthaceae family is a common flowering plant having enormous medicinal importance. It grows often as a weed in the rainy season. It is native of Central America but has spread in many tropical countries including India. The present study investigates the antioxidant property of aqueous leaf extract of this plant . The aqueous leaf extract was subjected to standard analytical methods for analysis of important phytochemicals, antioxidant content, lipid peroxidation and DPPH (2, 2-diphenyl-1-picryl-hydrazyl-hydrate) generated free radical scavenging properties. Effect of extract on pUC18 plasmid DNA was demonstrated by agarose gel electrophoresis. The metal chelating activity of leaf extract was studied by spectrophotometer. Result indicates presence of important phytochemicals in significant amount. The result highlighted the strong antioxidant activity of aqueous extract attributed to its polyphenolic compounds such as flavonoids. The aqueous extract of leaf protects plasmid DNA from oxidative stress in a dose-dependent manner. Single and double stranded nicks in plasmid DNA occurred when used above optimum concentration. The concentration of extract that protected DNA also demonstrated higher DPPH free radical scavenging activity, which showing strong positive correlation. The metal chelating activity of the same extract was profoundly exhibited. In conclusion, our results indicate that the leaves of the cracker plant contains important bio-actives compounds and are capable of protecting DNA against oxidative damage probably by acting as a strong antioxidant, but can also damage DNA when concentration exceeds the optimum level probably by acting as a strong pro-oxidant. [ABSTRACT FROM AUTHOR]