Effect of caffeic acid esters on antioxidant activity and oxidative stability of sunflower oil: Molecular simulation and experiments.

Polyphenol, though used as antioxidants in food industry, suffers from poor solubility issues in vegetable oil. Usually, its solubility would be enhanced through esterification. This work investigated the antioxidant activity and oxidative stability of caffeic acid (CA) and its derivative modified esters by molecular simulation and experiments. Density functional theory (DFT) and molecular dynamic analysis revealed the antioxidant mechanism of CA esters attributing to the comprehensive effects. The lower hydrogen dissociation energy (ΔG) of CA esters with catechol moiety caused the transformation of antioxidant into quinone via the double hydrogen atom transfer reaction. Particularly, the second reduced hydrogen dissociation energy was the keypoint. The strong non-bond energy and hydrogen bond allowed CA esters and oil molecules to interact more efficiently. Hence, the ester moieties enhanced the antioxidant activity with 4.5-6.5 % ΔG reduction compared to CA. Rancimat and DSC assays validated the theoretical predictions. This result shows that the antioxidant activity of CA and its esters could be predicted by this molecular simulation way, which may aid in designing of new polyphenol antioxidant structure.

Degradation characteristics of crude oil by a consortium of bacteria in the existence of chlorophenol.

In order to enhance the degradation effect of microorganisms on crude oil in the existence of chlorophenol compounds, oil-degrading bacteria C4 (Alcaligenes faecails), C5 (Bacillus sp.) and 2,4-dichlorophenol (2,4-DCP) degrading bacteria L3 (Bacillus marisflavi), L4 (Bacillus aquimaris) were isolated to construct a highly efficient consortium named (C4C5 + L3L4). When the compound bacteria agent combination by VC4: VC5: VL3: VL4 = 1:2:2:1, the crude oil degradation efficiency of 7 days was stable at 50.63% ~ 55.43% under different conditions. Degradation mechanism was analyzed by FTIR, GC-MS and IC technology and the following conclusions showed that in the system of adding consortium (C4C5 + L3L4), the heavy components were converted into saturated and unsaturated components. The bacterial consortium could first degrade medium and long chain alkanes into short chain hydrocarbons and then further degrade. And the dechlorination efficiency of 2,4-DCP in the degradation system reached 73.83%. The results suggested that the potential applicability and effectiveness of the selected bacteria consortium for the remediation of oil-contaminated water or soil with the existence of chlorophenol compound.

Effects of natural antioxidants on the oxidative stability of Eucommia ulmoides seed oil: Experimental and molecular simulation investigations.

Eucommia ulmoides seed oil with high health potential is prone to oxidative rancidity due to its rich unsaturated fatty acids. In this work, three natural antioxidants were selected for exploring the oxidation resistance of the oil compared with the common synthetic antioxidant BHT. Antioxidant activity and its dispersion and migration as well as oxygen barrier performance were predicted via the bond dissociation enthalpy (BDE), mean square displacement (MSD), binding energy (Ebinding) and permeability coefficient (S). The predicted comprehensive performance is as follows: myricetin > epicatechin > caffeic acid > BHT. Free radical scavenging assay and Rancimat assay confirmed the antioxidant activity and protective effect on oil. That is the protective effect of three natural antioxidants on Eucommia ulmoides seed oil is better than BHT and myricetin shows the optimal comprehensive performance. The induction period of myricetin/lipid system increased 164.5% compared with the control. The experimental results are in good consistent with the simulation predictions.