| Tocopherols,phytosterols and oryzanol are common lipid phytochemicals found in vegetable oils.However,whether there is a dose-effect relationship between the concomitant content and antioxidant capacity is still unknown.Additionally,the antioxidant capacity of plant oil is not devoted by the contribution of a single concomitant but all existent compounds in oil.Therefore,in this study,three typical lipid concomitants named ?-tocopherol,phytosterol and ?-oryzanol were chosen to investigate the interaction effects of scavenging radicals in three different medium by Bliss model.The research contents were as follows:Firstly,in the absolute ethanol polar system,the interaction types and mechanisms of three lipid concomitant for scavenging free radical were preliminarily explored.The results showed that the scavenging of free radicals after the combination of the three substances was mainly antagonistic.Among them,the SE values of 94.55 mg/kg ?-tocopherol+120.58 mg/kg ?-oryzanol,94.55 mg/kg ?-tocopherol+81.87 mg/kg phytosterol and 120.58 mg/kg ?-oryzanol+81.87 mg/kg phytosterol were 0.89,0.97 and 0.98,respectively.Subsequently,the mechanism of antagonism was explored from the perspective of reaction kinetics.When the reaction time was at 2 s,the rate of scavenging DPPH· for ?-tocopherol was faster than that of the mixture system,and the stoichiometric number of scavenging DPPH· for ?-tocopherol was 2.After mixing with ?-oryzanol and phytosterols,the stoichiometric number was less 1.Meantime,Fourier transform infrared was used to detect the mixture system,and the hydroxyl bond was found to shift to the right.It was speculated that the formation of hydrogen bonds may also lead to the rate of scavenging free radicals slowed down in mixture system.Thus,it was demonstrated that inhibition of the regeneration of ?-tocopherol and the formation of hydrogen bonds were the main causes of the antagonism for these three concomitants.Secondly,in the ethyl acetate non-polar system,the interaction types and mechanisms of scavenging free radical of three lipid concomitants at high concentrations were investigated.The results showed that the interaction of scavenging free radicals after the combination of the three substances was mainly antagonistic.Among them,after 500 mg/kg ?-tocopherol was compounded with 10000 mg/kg ?-oryzanol and 10000 mg/kg phytosterol,it showed antagonistic and additive effects,respectively.The SE value of 10000 mg/kg ?-oryzanol+10000 mg/kg phytosterol was 0.93 for antagonism.Subsequently,the kinetic study showed that the reaction rate of mixture system for scavenging radicals in the non-polar medium is mainly determined by the main antioxidant.Then the hydroxyl bond was shifted to the right was found by the Fourier transform infrared,which provide a basis that the formation of hydrogen bonds was also a possible cause of the antagonism of the three lipid concomitants in ethyl acetate.Finally,in the removal of concomitant rice oil,we studied the types and mechanisms of the interaction among three lipid concomitants including scavenging free radicals and oxidative stability after they were compounded.The results showed scavenging free radicals and oxidative stability of ?-oryzanol and phytosterols were synergistic effect.The antioxidant capacity and the oxidation induction time of 12000 mg/kg ?-oryzanol+ 12000 mg/kg phytosterol reached 211 ?mol TE/100 g and 4.21 h,which was higher 11%,8.7% than that of theoretical value,respectively;The other two combinations of scavenging free radicals and oxidative stability interactions showed antagonism.The scavenging capacity and oxidation induction time of 1000 mg/kg ?-tocopherol+12000 mg/kg ?-oryzanol were 264 ?mol TE/100 g,5.5 h respectively,which were 7% and 35% lower than that of the theoretical value.The scavenging capacity and oxidation induction time of 1000 mg/kg ?-tocopherol and 12000 mg/kg phytosterol were 238 ?mol TE/100 g,respectively 4.05 h respectively,which were both lower 9% than that of the theoretical value.Meanwhile,Fourier transform infrared was used to detect the spectrum of mixture system.No hydrogen bond was detected,which may be due to the complex composition of rice oil.In summary,the concentration of lipid concomitants and medium have significant effects on the type of anti-oxidation interactions.In the two solvent media,the three lipid concomitants exhibited antagonism,while in the rice oil medium,?-oryzanol and phytosterols was found synergistic,?-tocopherol and other two concomitant were found antagonism.Inhibition of ?-tocopherol regeneration and formation of hydrogen bonds may be the main cause of interaction between the three concomitants. |
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