A Study of Interaction Between α-Tocopherol Acetate and Fatty Acids Mixed with Polyethoxylated Phospholipid in Langmuir Monolayer at Air-Aqueous Interface

alpha-Tocopherol acetate is a specific type of vitamin E and categorized as a water-insoluble substance and widely used as an antioxidant. Molecular interactions among fatty acid/polyethoxylated phospholipid with alpha-tocopherol acetate is of the interest in this study. The effect of the amount alpha-tocopherol acetate on the thermodynamic properties of mixed monolayer fatty acid/polyethoxylated phospholipid monolayers is revealed from the surface pressure - area (pi - A) isotherm. The relevant thermodynamic parameters such as miscibility, surface excess area, compression modulus, and stability of the mixed monolayer on phosphate buffer subphase can be analyzed quantitatively from this study. We found that the mixed monolayer either binary or ternary mixture consisting fatty acid with and without the presence of polyethoxylated phospholipid is miscible with alpha-tocopherol acetate. The compatibility of alpha-tocopherol acetate with fatty acid and the mixture of fatty acid/polyethoxylated phospholipid monolayer relied on acyl chain length and degree of unsaturation of fatty acid. Moreover, molecular weight of polyethoxylated phospholipid also plays a significant role in determination of monolayer stability. The most favorable combination of each mixture is determined. These findings provide valuable information for formulation and encapsulation of alpha-tocopherol acetate in fatty acid vesicles in addition to promote the understanding of interaction between fatty acid, polyethoxylated phospholipid, and alpha-tocopherol acetate.