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

Ferulic acid and its derivative gamma-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 gamma-oryzanol effect of fighting with ultraviolet irradiation. We demonstrated that both ferulic acid and gamma-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 S(1)states decay to the S(0)state via internal conversion (IC) process at the S-1/S(0)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 gamma-oryzanol as UV protection in rice from our excited state non-adiabatic dynamics. [GRAPHICS] .

Automated summary

Ferulic acid and gamma-oryzanol in rice demonstrate strong UV absorption capabilities and excellent photostability. Through calculations, it is found that they decay from the excited state to the ground state via internal conversion process and undergo photoisomerization. This study provides insight into the UV protection mechanism of ferulic acid and gamma-oryzanol in rice based on excited state non-adiabatic dynamics.