Potenciais alelopáticos e antioxidante de Portulaca oleracea L. e Raphanus raphanistrum L.

Abstract

This work aimed to evaluate the allelopathic potential, antioxidant and quantification of total phenolic compounds of different extracts from the dried leaves of Portulaca oleracea (purslane) and Raphanus raphanistrum (turnip). The extracts were prepared by refluxing in ultrapure water and dynamic maceration used increasingly polar solvents (hexane, dichloromethane, ethyl acetate, butanol and ultrapure water). The extracts were f iltered and evaporation in vacuum then were performed calculations of extractives yields and quantification of total phenolic assays (phenols, flavonoids and dihidroflavonoides) and antioxidant potential (reducing power, total antioxidant capacity, chelating power and sequestration DPPH free radicals). Correlations of quantification methods and antioxidant were obtained by canonical correlation analysis. To test allelopathy extracts were resuspended in ultrapure water, pH mesurado and diluted so as to obtain four concentrations (2, 4, 6, 8 g.L -1 ). In germination bioassays were used 25 seeds of Lactuca sativa (lettuce) and wetted with 4 mL of the extracts and kept in an incubator BOD with temperature at 24 ° C and photoperiod of 12 hours were evaluated in the germination speed index (GSI) , germination percentage (%G), dry mass, root and hypocotyl growth. Regardless of extractive methods, the aqueous extracts showed the highest yield for both plants. The extracts, only the hexane extract showed no significant results in quantitation assays and antioxidant. In the test of the chelating power aqueous extracts of turnip showed better chelation activity of Fe +2 (0.002 ± 0.0 mg / mL). In the butanolic purslane extract showed a high antioxidant effects in the test of reducing power compared to ascorbic acid. Both species have a high correlation between the quantification of phenolic compounds and antioxidant methods. In allelopathy test aqueous extracts obtained by maceration and flow of turnip showed allelopathic effect from lower concentrations, and in the aqueous extract by steeping in the highest concentration (10 g.L -1 ) inhibited the total germination of lettuce seeds. The extracts obtained from the dichloromethane solvent, ethyl acetate, butanol and ultrapure water influenced the development of the seedlings of the test species, wherein the aqueous extract was able to inhibit more than 50% of root growth. In purslane, the aqueous extracts obtained by reflux and maceration showed the activity in all analyzed tests, but the extract obtained by maceration method was the one that demonstrated best results, completely inhibiting germination at concentrations of 8:10 g L -1 . Extracts with increasing polarities only dichloromethane did not affect the development of lettuce. The results of this study indicated the allelopathic and antioxidant potential of purslane and turnip in trials in vitro.