engleski

Application of Mathematical Models in Simulation of DPPH Disappearance kinetics in Croatian Pumpkin (Cucurbita pepo L.) Seed Oils

In this study, the antioxidant activity of three pumpkin seed oil groups (cold-pressed, traditionally produced and salad) from the northern part of Croatia and the kinetics of their behavior as free radical scavengers were investigated using DPPH radicals. In addition, the involvement of oil tocopherol isomers (α-, γ- and δ-) in different phases of DPPH disappearance as well as their impact on the rate of reaction were analyzed. The kinetics of DPPH disappearance were found to be a two-step process. In the first phase, rapid disappearance of DPPH occurs during the first 11 minutes of the reaction, depending on the oil sample, followed by a slower, second phase decline. To describe DPPH disappearance kinetics, six mathematical models (mono and biphasic) were tested. The better applicability of biphasic models (first-order double-exponential and Weibull distribution models) in the description of DPPH disappearance is confirmed by the high coefficients of determination and low error values. Our findings showed that γ- and δ-tocopherols affected DPP disappearance during the first phase, while α-tocopherol was involved in the second phase of the reaction. Moreover, α-tocopherol demonstrated 30 times higher antioxidant activity than γ- and δ-tocopherols. The results of this study indicate the biphasic double-exponential behavior of DPPH disappearance in oils, due to the complexity of reactions that involve different tocopherols isomers and proceed through different chemical pathways. This means that tocopherol isomers presented in the oils possess different radical suppressing ability and that they react at different rates with radicals, thereby causing the reaction to occur in two phases.

DPPH; mathematical modelling; pumpkin-seed oil; radical scavenging activity; tocopherols

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