Characterization of daidzein associates in soybean oil and their interactions with phosphatidylcholine reversed micelles

Background. Soybean oil is one of the most commonly consumed vegetable oils in the world. It is rich in unsaturated fatty acids and contains surface-active compounds which, due to their amphiphilic nature, are capable of forming association colloids. These structures are considered to be autoxidation centers. Interactions of amphiphilic antioxidants present in soybean oil and association colloids may influence their solubility and antioxidant activity, as well as changing the organoleptic properties of the oil (such as opacity). The aim of this study was to characterize the interactions of isoflavone daidzein (DAI) with phosphatidylcholine association colloids (reverse micelles) and get insights into the aggregates formed from daidzein itself in soybean oil.
Materials and methods. In this investigation, static and dynamic light scattering techniques (SLS, DLS) were applied to take measurements. Association colloids (reverse micelles) containing daidzein were formed from DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) in soybean oil from which the amphiphilic minor components were removed.
Results. Daidzein was found to be able to self-assemble and form associates in soybean oil, as well as incorporating itself into DOPC reverse micelles. This antioxidant increases the hydrodynamic diameter of DOPC structures only above a specified critical concentration (600 μmol/kg according to DLS measurements), while structures composed of DAI are formed at its lower concentrations (above 50 μmol/kg as measured by SLS).
Conclusions. The present findings may help in the formulation of oils that possess health protecting properties with an increased daidzein content and in the elucidation of daidzein antioxidant action mechanisms in bulk oils.