Pectin gel and retinyl palmitate-loaded monoolein cubic phases as a salt-responsive and anti-oxidative vehicle

Pectin gel and retinyl palmitate (RP)-loaded monoolein (MO) cubic phases were prepared by a melt-hydration method as a salt-responsive and anti-oxidative vehicle. The pectin gel was formed maximally when CaCl₂ concentration in aqueous pectin solution (0.25% to 2%) was 50 mM. The phase transition temperature (PTT) of the cubic phase, determined by differential scanning calorimetry (DSC), decreased from 58 to 46.9 ℃ as the RP content increased from 0 to 1.5%. The maximum release degree at 22 ℃ of a dye (amaranth) loaded in a cubic phase was about 15.9% and 51.3%, respectively, when the release medium was deionized water and PBS (10 mM, pH 7.4). An ion exchange between Na⁺ and Ca²⁺ seemed to cause the extensive release in the saline. The in vitro radical scavenging capability (RSC) of RP loaded in the cubic phase was proportional to the RP concentration and the RSC was substantially higher than that of free RP. The double bond of MO contained in the cubic phases was chemically stable during 6 months storage at 25 ℃ and 40 ℃, evidenced by ¹H NMR spectroscopy. The cubic phases maintained their integrity and retained their unique structure (the water channels winded by the lipid layers) under the same storage conditions.