Effect of DPPC on the Kinetics of Photo‐ and Thermal Isomerization of γ–Oryzanol

ABSTRACT Gamma oryzanol is extracted from rice bran oil and has potential applications in the cosmetics industry with products such as sunscreens due to its photo sensitivity. In this work, we have studied the quasi‐two‐dimensional phases exhibited by the mixtures of DPPC and ‐oryzanol at the air‐water interface and the kinetics of isomerization of ‐oryzanol in the mixed monolayer. The rate constants corresponding to the photo‐and thermal‐isomerization processes are obtained for different mole fractions of DPPC in the ‐oryzanol‐DPPC mixed monolayers. The kinetic studies at different temperatures show the Arrhenius temperature dependence of photo‐and thermal‐isomerization processes for the trans to cis ‐state isomerization of ‐oryzanol molecules and vice versa, respectively. Our analysis shows that the ‐oryzanol molecules in cis ‐state are more stable than the trans ‐state for the monolayer mixtures containing DPPC with a relative composition of 0.2 and 0.3.