Determination of Antioxidant and Antimicrobial Activities of Rumex crispus L. Extracts

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Abstract
The antioxidant activities, reducing powers, 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities, amount of total phenolic compounds, and antimicrobial activities of ether, ethanol, and hot water extracts of the leaves and seeds of Rumex crispus L. were studied. The antioxidant activities of extracts increase with increasing amount of extracts (50−150 μg). However, the water extracts of both the leaves and seeds have shown the highest antioxidant activities. Thus, addition of 75 μg of each of the above extracts to the linoleic acid emulsion caused the inhibition of peroxide formation by 96 and 94%, respectively. Although the antioxidant activity of the ethanol extract of seed was lower than the water extract, the difference between these was not statistically significant, P > 0.05. Unlike the other extracts, 75 μg of the ether extract of seeds was unable to show statistically significant antioxidant activity, P > 0.05 (between this extract and control in that there is no extract in the test sample). Among all of the extracts, the highest amount of total phenolic compound was found in the ethanol extract of seeds, whereas the lowest amount was found in the ether extract of seeds. Like phenolic compounds, the highest reducing power and the highest DPPH scavenging activity were found in the ethanol extract of seeds. However, the reducing activity of the ethanol extract of seeds was ∼40% that of ascorbic acid, whereas in the presence of 400 μg of water and ethanol extracts of seeds scavenging activities were about 85 and 90%, respectively. There were statistically significant correlations between amount of phenolic compounds and reducing power and between amount of phenolic compounds and percent DPPH scavenging activities (r = 0.99, P < 0.01, and r = 0.864, P < 0.05, respectively) and also between reducing powers and percent DPPH scavenging activities (r = 0.892, P < 0.05). The ether extracts of both the leaves and seeds and ethanol extract of leaves had shown antimicrobial activities on Staphylococcus aureus and Bacillus subtilis. However, none of the water extracts showed antimicrobial activity on the studied microorganisms. Keywords: Antioxidant activity; reducing power; antimicrobial activity; Rumex crispus L.; DPPH scavenging