1-2-oleoylphosphatidylcholine and 6-hydroxy-2-5-7-8-tetramethylchroman-2-carboxylic-acid

Phospholipids self-assemble in bulk oils to form structures such as reverse micelles that can alter the microenvironment where chemical degradation reactions occur, such as lipid oxidation. In this study, we examined the influence of phospholipid reverse micelles on the activity of non-polar (α-tocopherol) and polar (Trolox) antioxidants in stripped soybean oil (SSO). Reverse micelles were formed by adding 1000 μM 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) to SSO. The addition of DOPC reverse micelles had a prooxidant effect, shortening the lag phase of SSO at 55 °C. DOPC improved the activity of low α-tocopherol or Trolox concentrations (10 μM) but decreased the activity of high concentrations (100 μM). Hydrophilic Trolox had better antioxidant activity than hydrophobic α-tocopherol. Fluorescence steady state and lifetime decay studies suggests that differences in the antioxidant activity of Trolox and α-tocopherol could be due to differences in their physical location in DOPC reverse micelles. These results will improve our understanding and control of lipid oxidation in bulk oils.

Topics: alpha-Tocopherol; Antioxidants; Chromans; Lipid Metabolism; Micelles; Oils; Phosphatidylcholines; Phospholipids; Soybean Oil

An in vitro antioxidant assay has been developed to better reflect the in vivo conditions of antioxidants interacting with membrane and lipid surfaces. The lipid peroxidation inhibition capacity (LPIC) method measures the ability of both lipophilic and hydrophilic antioxidants to protect a lipophilic fluorescent probe 4, 4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid, incorporated in the membrane, from 2,2'-azobis(2-amidinopropane)hydrochloride generated radicals in the surrounding aqueous solution. Antioxidant activities of test compounds were measured either after they were mixed with preformed liposomes (LPIC(Mixed)) or after they were incorporated into liposomes (LPIC(Inco)) as they were made. The results were analysed to determine how the method of mixing and the structures of the antioxidants influenced their protection of the membrane from free radical attack. The LPIC(Mixed) values were larger than the LPIC(Inco) values for a range of 12 structurally diverse antioxidant compounds. However, there was no linear correlation between the lipophilicities, as measured by their partition coefficient, log P and either LPIC(Inco) or LPIC(Mixed) values. A strong correlation was found between LPIC(Inco) and LPIC(Mixed) values.

Topics: alpha-Tocopherol; Antioxidants; beta Carotene; Boron Compounds; Chromans; Coumaric Acids; Flavonoids; Fluorescent Dyes; Free Radicals; Gallic Acid; Lipid Peroxidation; Liposomes; Oxidation-Reduction; Phase Transition; Phosphatidylcholines

Topics: Antioxidants; Carotenoids; Chromans; Free Radical Scavengers; Indicators and Reagents; Kinetics; Liposomes; Phosphatidylcholines; Retinoids; Vitamin E