Antioxidant properties and phenol content of Portulaca oleracea L. leaf, stems and flowers infusions: health benefits

Dissertação de mest., Ciências Biomédicas, Departamento de Ciências Biomédicas e Medicina, Univ. do Algarve, 2011

The present study analyzes the antioxidant properties of Portulaca oleracea, common known as purslane. This plant is an interesting object of study because it is a naturally occurring widely distributed plant and it was used for centuries in folk medicines all around the world. Samples were harvested in two different locations, one from Algarve (location 1) and another from Alentejo (location 2), and divided in three different parts: leaves, stems and flowers. Then, they were dried in an incubator, powdered and water extracts were performed and analyzed. Total antioxidant activity, total phenolic content, condensed tannins, reducing power, and ferric-reducing antioxidant power assays showed significant higher values (P<0,05) in location 2 rather than in location 1, and generally stems present the same pattern when comparing to other plant parts. Moreover, good correlations were found between TPC and all the other assays, which suggest that in purslane the antioxidant activity and reducing power are essentially due to the content of phenolic compounds. Also DPPH and ABTS assays present better results in location 2, since it was needed lower concentrations to inhibit 50% of the free radicals in solution than in location 1. On the other hand, for total flavonoids content only stems present this significant difference and for total monomeric anthocyanins and total carotenes higher concentrations were presented by location 1. The same seems to happen with individual analysis of phenolic acids and flavonoids by liquid-chromatography, where methanol extracts were used. Also, DNA nicking assay showed that water extracts of purslane effectively protect DNA from oxidative damage of hydroxyl radicals. As general conclusion of this study it is possible to state that both location and plant parts have a significant interference on antioxidant activity and that Portulaca oleracea is a rich source of antioxidants among other compounds with a great number of potential benefits for human health.