Free radical scavenging activity of carbonyl‐amine adducts formed in soybean oil fortified with phosphatidylethanolamine

Abstract

Non‐enzymatic browning reactions between lipid aldehydes and aminophospholipids might play an important role in the oxidative stability of cold‐pressed vegetable oils. We, therefore, aimed to study the Maillard‐type reaction between hexanal, a lipid oxidation product of linoleic acid, and phosphatidylethanolamine (PE (16:0/18:1)) at a ratio of 2:1 at conditions representative of the extraction of cold‐pressed soybean oils (CPSBO) and determine the radical scavenging activity of the carbonyl‐amine adducts with the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay. The reaction product, 2‐pentyl‐3,5‐dibutyl‐dihydropyridine, could be identified by means of LC‐ESI‐QTOF-MS/MS. The formation of this nitrogen‐containing heterocycle significantly increased with time and temperature (p < 0.05). The products formed during the carbonyl‐amine reaction between PE (16:0/18:1) and hexanal at 60 °C showed a radical scavenging activity of approximately 20% (p < 0.05). The fraction, containing 2‐pentyl‐3,5‐dibutyl‐dihydropyridine, contributed to, but was not solely responsible for, the radical scavenging activity (p < 0.05). Incubation of CPSBO fortified with PE (16:0/18:1) at 60 °C for 60 min had the strongest radical scavenging activity of 85.1 ± 0.62%. Besides 2‐pentyl‐3,5‐dibutyl‐dihydropyridine, other carbonyl‐amine adducts might impact the radical scavenging activity of CPSBO as well. The oxidative stability of CPSBO might be increased by promoting the formation of carbonyl‐amine reaction products, such as 2‐pentyl‐3,5‐dibutyl-dihydropyridine.