Determination of pH Effects Phosphatidyl-hydroxytyrosol and Phosphatidyl-tyrosol bilayer behavior

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

Submitted to: Methods and Protocols
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2018
Publication Date: 11/9/2018
Citation: Evans, K.O., Compton, D.L., Appell, M.D. 2018. Determination of pH Effects Phosphatidyl-hydroxytyrosol and Phosphatidyl-tyrosol bilayer behavior. Methods and Protocols. 1(4):41. doi:10.3390/mps1040041.
DOI: https://doi.org/10.3390/mps1040041

Interpretive Summary: Fats and oils in food products are often vulnerable to spoilage, so producers often add antioxidants to prolong the shelf life and maintain nutritive quality. However, not all antioxidants mix well with fats and oils. One way to resolve this issue is to make the antioxidants more oil-like by attaching the antioxidant to an oil molecule. We developed two newly synthesized bio-based “oily-antioxidants that are capable of reducing this spoilage, and have characterized their physical properties in this study. These novel bio-based lipids were enzymatically synthesized from olive oil waste components and soybean oil. These oily-antioxidants were organized into sub-microscopic spheres and characterized for physical stability and mechanical properties under different pH conditions. This work further highlights technology that uses enzymes to attach natural plant components from olive oil waste to soybean oil. This research explains that the new antioxidant compounds are highly stable spherical nanostructures that resist physical changes at various solution conditions. This agricultural research supports the development of value-added, commodity oil-based commercial products and is an essential component of establishing a bio-based economy and expanding markets for agricultural producers.

Technical Abstract: Enzymatically synthesized hydroxytyrosol and tyrosol phospholipids were investigated for liposomal behavior at buffer conditions pH 5.5, 7.5 and 10. Bilayer formation, stability and adsorption properties were explored using dynamic light scattering, zeta potential measurements and quartz crystal microbalance with dissipation monitoring (QCMD), respectively. Liposome diameters were found to typically increase from pH 5.5 to pH 10. Zeta potential values, on the other hand, were found to be well below -25 mV at all pH conditions explored, indicating the lowest value (and thus best liposome stability) at pH 5.5 or pH 10. QCMD measurements demonstrated that 100% 1,2-dioloeoylphosphatidyl-hydroxytyrosol (DOPHT) liposomes adsorbed intact onto silica in buffer conditions at pH 5.5 and with no calcium, or at pH 7.5 with calcium (no adsorption was detected at pH 10). 1,2-dioleoylphosphatidyl-tyrosol (DOPT) liposomes was shown to adsorb intact under buffer conditions only at pH 5.5 with and without calcium. 1,2-dioleoylphosphatidyl-2-phenolethanol (DOPPE), in comparison, readily adsorbed intact at pH 7.5 without calcium present and just slightly at pH 5.5 with calcium present but formed a supported bilayer over hours at pH 5.5 in the absence of calcium ions.