Non-adiabatic Dynamics Mechanism in Excited State of Novel UV Protective Sunscreen in Rice: Conical Intersection Promotes Internal Conversion

Abstract

Ferulic acid and its derivative γ-oryzanol are common in Rice. They have the same molecular skeleton with some sunscreens that used commonly, but there were no reports on them as rice UV protection. In this work, UV absorption and fluorescence emission spectrum are performed to measure ferulic acid and γ-oryzanol effect of fighting with ultraviolet irradiation. We demonstrated that both ferulic acid and γ-oryzanol have good absorption intensity at UVA, UVB and UVC regions, with superior photostability. Furthermore, the optimized molecular conformation and potential energy surfaces (PES) in ground and excited states are obtained by using the time-dependent density functional theory (TD-DFT) method. From the calculation results, it can conclude that their S1 states decay to the S0 state via internal conversion (IC) process at the S1/S0 conical intersection (CI) point of PES followed by trans–cis photoisomerization. For the first time, we elucidated the mechanism of UV protection for ferulic acid and γ-oryzanol as UV protection in rice from our excited state non-adiabatic dynamics.