Phytochemical Composition and Antioxidant Activity of Portulaca oleracea: Influence of the Steaming Cooking Process

In this work, we compared the phenolic composition and antioxidant capacity of methanolic extracts of raw and steamed aerial parts of Portulaca oleracea L. Two new cyclo-dopa amides were identified, named oleraceins X and Y, along with six known ones (oleraceins A, B, C, N, J, and U). Compounds identification and quantification were done by high-performance liquid chromatography with diode array and mass spectrometry detections. The most abundant compounds were phenolic alkaloids (oleraceins), and the main quantified compounds were isocitric and citric acids, with concentrations of 500–550 and 440–600 mg/100 g dried extract, respectively. The study of both the influence of the steaming process in Portulaca oleracea L. and total phenolic content and radical scavenging assays (ABTS(·+) and DPPH) were also carried out. The total individual phenolic content of raw Portulaca decreased from 1380 mg/100 g DE to 1140 mg/100 g DE after the steaming process. The antioxidant capacity in ABTS and DPPH assays decreased approximately 50 and 40%, respectively, after samples were cooked by steaming. The raw extracts presented the highest concentration of bioactive compounds, as well as higher antioxidant and radical scavenging values.