Evaluation of in vitro antioxidant and brine shrimp lethality bioassay of different extracts of Polygonum plebeium R. Br.

Antioxidants are substances which has the ability to scavenge free radicals and help to decrease the incidence of oxidative stress induced damage. As synthetic antioxidants have some side effect, now a day’s great deal of effort being expanded to find effective antioxidant from natural sources for the treatment and prevention of oxidative stress induced damage. Polygonum plebeium R. Br. (Family: Polygonaceae) commonly known as “Chemti sag”, “Dubia Sag”, “Anjaban” is widely distributed in Bangladesh and used as a vegetable. The present study was carried out to investigate antioxidant and cytotoxic potential of aerial parts of Polygonum plebeium R. Br. in vitro. The aerial parts of the plant were extracted with different solvents (petroleum ether > ethyl acetate > methanol > water) i.e. from non-polar to polar. Preliminary phytochemical screening confirmed the presence of flavonoids, alkaloids, glycosides, steroids, saponins and carbohydrates. All the extracts showed promising antioxidant and cytotoxic potential. Methanolic extract was found to contain highest amount of phenolic compounds ((7.773 ± 0.547 mg/g GAE) and flavonoids contents was highest in petroleum ether extracts (11.88 ± 0.204 mg/g QE). Both the methanolic and ethyl acetate extracts showed to have possessed similar total antioxidant capacity and expressed as ascorbic acid equivalents. In DPPH free radical scavenging assay, methanolic extracts showed highest scavenging potential with IC50 value of 43.63 µg/ml followed by ethyl acetate extracts with IC50 value of 72.62 µg/ml compared to standard ascorbic acid having IC50 value of 18.34 µg/ml. Both methanolic and water extracts had similar nitric oxide scavenging potential and were highest among the extracts. Reducing power was found to increase with increasing the concentration of the plant extracts and the extracts were found to contain low amount of alkaloids. In brine shrimp lethality bioassay, water extracts of the plant showed most potent cytotoxic action with LC50 value of 23.72 µg/ml followed by the petroleum ether extracts with LC50 value of 46.04µg/ml where standard cytotoxic agent vincristine used as positive control. This study provides scientific basis for the use of Polygonum plebeiumR. Br. as a natural antioxidant.