Search

In the present work, the effect of refining process on physicochemical parameters (acid and peroxide values), chemical compositions (fatty acid and phytochemical contents) and in vitro antioxidant activities of rice bran oil (RBO) were investigated. The results showed that acid and peroxide values of the test RBOs decreased significantly after the refining process. However, refining did not have significant influence on the fatty acid composition. Besides, phytochemical levels (except tocopherols) and antioxidant activities of the RBO were reduced to a large degree during the refining. Among the steps of RBO refining, neutralization caused the largest losses of phytochemicals and antioxidant activities. According to the correlation analysis, polyphenols were significantly positive correlated with ABTS and ORAC values, while γ-oryzanol was significantly positive correlated with DPPH and CAA values. Chemometrics was employed to evaluate the certain contribution of phytochemical to the antioxidant activity, and the measures that can be taken to reduce the loss of phytochemical levels in each step of the RBO refining process were also provided. • Refining process resulted in a decline in phytochemicals except tocopherols. • Refining process led to a decreased in vitro antioxidant activities. • The antioxidant activity was significantly correlated with polyphenols and γ-oryzanol. [ABSTRACT FROM AUTHOR]

• Concentration of binary mixtures affected the total antioxidant capacity. • Ratio of binary mixtures affected the type or degree of antioxidant interaction. • Inhibition of phytosterol on α-tocopherol regeneration leads to antagonism. • Synergism of γ-oryzanol and phytosterol is related to the hydrogen bond. In this study, purified rice bran oil (RBO) was used as a lipid matrix model to study the individual and binary antioxidant capacity of the minor constituents (α-tocopherol, γ-oryzanol and phytosterol) added at different concentrations and ratios. The results revealed that concentration influenced on the oxidation stability and scavenging capacity, while ratio mainly affected the type of interaction or the degree of synergism or antagonism. It was important to notice that the antioxidant capacity of α-tocopherol would decrease under high concentration. Besides, the inhibition of phytosterol on α-tocopherol and the formation of hydrogen bond between γ-oryzanol and phytosterol were speculated by the interactions of these minor constituents. This work helps to select efficient combinations for stabilizing the anti-oxidation of nutrient enriched RBO or provide suggestions for moderate retain of minor constituents in RBO. [ABSTRACT FROM AUTHOR]

In this study, the cellular antioxidant activity (CAA) of α-tocopherol and γ-oryzanol was determined in two typical oil bases, namely rice bran oil base (RBOB) with long-chain unsaturated triglycerides and coconut oil base (CNOB) with medium-chain saturated triglycerides. The results showed that α-tocopherol and γ-oryzanol exhibited significantly higher CAA values in CNOB. In order to further explore the mechanism, glyceryl trioleate (GLT) and medium chain triglycerides (MCT) with similar structures to RBOB and CNOB respectively were added and compared. It was found that long-chain unsaturated triglycerides (RBOB and GLT) in emulsions exhibited lower CAA values than medium-chain saturated triglycerides (CNOB and MCT), though the former presented higher cellular uptake of minor constituents. It was speculated that unsaturated bond tended to be attacked by free radicals to initiate an oxidative chain reaction in HepG2 cells resulting in lipid peroxidation, thus depleted more antioxidants. Overall, these findings provided useful reference for further developing the production and processing of vegetable oil for better stability. • Medium-chain saturated glycerides exhibited better cellular antioxidant activities. • Long-chain unsaturated glycerides were more conducive to the cellular uptake. • Type of glycerides has greater effect on cellular antioxidant activity than cellular uptake of minor constituents. [ABSTRACT FROM AUTHOR]

Lipid concomitants are the main trace substances that determine the oxidative stability of oils. Over 90% of oils are composed of triglycerides, which affect oxidative stability. Oils typically enter living organism as emulsions. This study investigated the physical properties and cellular antioxidant activity (CAA) of emulsions in two model oils, namely, rice bran oil (RBO) with long-chain unsaturated triglycerides and coconut oil (CNO) with medium-chain saturated triglycerides. The results were as follows: the mean particle sizes were all approximately 250 nm; the polydispersity index (PDI) values were below 0.2; and the zeta potential values were more negative than −30 mV. The droplet size distribution of CNO emulsions was more concentrated than that of RBO emulsions. Rice bran oil-S (RBO-S) emulsions exhibited the highest CAA value, but the CAA value of coconut oil-C (CNO–C) emulsions was higher than that of rice bran oil-D (RBO-D) emulsions, indicating that CAA was influenced by the combined effect of triglycerides and minor constituents. Moreover, the medium-chain saturated triglycerides in vegetable oil emulsions resulted in a stronger CAA than that of long-chain saturated triglycerides. • Emulsions rich in long-chain unsaturated triglycerides are more dispersed in size distribution. • Oil with medium-chain saturated triglyceride is easier to result in strong CAA in oil emulsions. • The result of CAA was the combined effects of triglycerides and micronutrients of the vegetable oil. [ABSTRACT FROM AUTHOR]