Charged phospholipid effects on AAPH oxidation assay as determined using liposomes

Authors: Evans, Kervin; Compton, David - Dave; Kim, Sanghoon; Appell, Michael

Submitted to: Chemistry and Physics of Lipids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2019
Publication Date: 2/21/2019
Citation: Evans, K.O., Compton, D.L., Kim, S., Appell, M.D. 2019. Charged phospholipid effects on AAPH oxidation assay as determined using liposomes. Chemistry and Physics of Lipids. 220:49-56. https://doi.org/10.1016/j.chemphyslip.2019.02.004.
DOI: https://doi.org/10.1016/j.chemphyslip.2019.02.004

Interpretive Summary: Long-term storage can be detrimental to vegetable oils and fats because oxygen slowly breaks down the products through a process called oxidation, causing them to become rancid. This deterioration not only shortens the shelf life of the oils and fats, but also results in a loss in quality for food and industrial applications. Thus, finding simple methods to limit or prevent oxidation of vegetable oils and fats is important. Current research shows that negatively charged compounds can speed up the oxidation process of oil and fat products. This new study shows that positively charged compounds can retard the oxidation process, thus limiting the detrimental effects of oxygen. This research presents a highly effective method to increase the shelf life of products made from oils and fats, further increasing vegetable oils’ market value.

Technical Abstract: The capacity of molecules to inhibit oxidation is widely tested using liposomes as host matrices of the antioxidant molecule of interest. Spectroscopic assays are readily used for this purpose, specifically assays using 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH). In this work the effect that charged lipids have on an AAPH antioxidation assay using 4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid (C11-BODIPY® 581/591) as the reporter molecule was investigated. We measured the diameter, zeta potential and spectroscopic rate of decay and area-under-the-curve (AUC) associated with liposomes containing C11-BODIPY® 581/591 at varying molar percentages (0 to 10 mol%) of charged (cationic or anionic) lipids and compared the results. We showed that although increasing amounts of cationic or anionic lipids did change the diameter of the liposomes, size had little to no effect on the area-under-the-curve or decay rate of fluorescence. Increased (more positive) or decreased (more negative) zeta potentials did, on the other hand, affect the spectroscopic decay rates and area-under-the-curve. The results demonstrate the importance of considering the presence of charged lipids in the AAPH antioxidation assay.