Phytochemical characterization of soybean oil with addition of Portulaca oleracea L. extract

ABSTRACT The main objective of the present work was to measure the total phenolic compound content and antioxidant activity of Portulaca oleracea L. extract, besides evaluating the oxidative stability and phytochemical compound retention present in soybean oil plus synthetic (TBHQ and BHT) and natural (Portulaca oleracea L. extract) antioxidants. The treatments soybean oil (SO), soybean oil plus 100 mg/kg TBHQ (TBHQ), soybean oil plus 100 mg/kg BHT (BHT), and soybean oil plus 100 mg/kg extract (Extract) were subjected to thermo-oxidation at 180 ºC/5 h. The extract presented 99.5 mg EAG/100 g of total phenolic compounds and 84.6, 35.5, and 1.8µM Trolox/100 g of antioxidant activity to DPPH, β-carotene/linoleic acid system, and FRAP, respectively. The oxidative stability for the Extract treatment was inferior to TBHQ, which showed the longest induction period (7.6 h). After heating, TBHQ and Extract treatments presented higher capacity of tocopherol and phytosterol retention, reaching values over 88 and 87%, respectively. Similar percentages of polyunsaturated fatty acids were found in SO and Extract treatments. The purslane extract in the 100 mg/kg concentration reduced the alterations suffered by soybean oil after heating and it can be used as a natural substitute for synthetic antioxidants.