Phosphatidyl-hydroxytyrosol and phosphatidyl-tyrosol bilayer properties

Authors: Evans, Kervin; Compton, David - Dave

Submitted to: Chemistry and Physics of Lipids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2016
Publication Date: 12/14/2016
Publication URL: http://handle.nal.usda.gov/10113/5602250
Citation: Evans, K.O., Compton, D.L. 2017. Phosphatidyl-hydroxytyrosol and phosphatidyl-tyrosol bilayer properties. Chemistry and Physics of Lipids. 202:69-76.

Interpretive Summary: Oxidation causes oils and fats in foods to deteriorate during storage. This deterioration of the oils and fats reduces the foods’ shelf-life and quality, thus proving a need to limit or prevent the loss. Plant-based antioxidants have been shown to slow or prevent oxidation but cannot always be easily mixed with fats and oils. Our research using enzymes to create new valuable bioactive molecules has demonstrated that antioxidants from olive oil waste can be coupled to phospholipids from soy beans to form a new “antioxidant phospholipid." This research describes the synthesis of two antioxidant phospholipids. It also shows that these new antioxidant phospholipids have the ability to self-organize into stable spherical nanostructures that mix well with water-based solutions and offers insight into the nanostructure physical properties. This work demonstrates further the suitability of combining antioxidants from agricultural waste with a soy-based lipid matrix, further expanding markets for vegetable oils.

Technical Abstract: Hydroxytyrosol and tyrosol phospholipids were enzymatically synthesized and investigated for their bilayer properties. Dynamic light scattering demonstrated that hand extrusion at 100 nm consistently resulted in liposomes of nearly 85 nm diameter for both phosphatidyl-hydroxytyrosol (DOPHT) and phosphatidyl-tyrosol (DOPT). Transmission electron microscopy showed DOPT and DOPHT liposomes extruded at 100-nm to be spherical and non-distinctive from one another. Zeta potential measurements resulted in surface charges < -25 mV, demonstrating both DOPT and DOPHT form highly stable liposomes. Quartz crystal microbalance with dissipation monitoring measurements demonstrated that liposomal adsorption was dependent on a combination of DOPT (or DOPHT) mole-percent and calcium ions concentration. Fluorescence anisotropy measurements indicated that melting temperatures of DOPT and DOPHT were below 4 °C, suggesting that adsorption behavior and liposome formation was limited by electrostatic interactions and not gel-state formation.